Expressions de requête

  • Article

Les expressions de requête vous permettent d’interroger une source de données et de placer les données dans la forme souhaitée. Les expressions de requête prennent en charge LINQ en F#.

Syntaxe

query { expression }

Notes

Les expressions de requête sont un type d’expression de calcul similaire aux expressions de séquence. De la même façon que vous spécifiez une séquence en fournissant du code dans une expression de séquence, vous spécifiez un ensemble de données en fournissant du code dans une expression de requête. Dans une expression de séquence, le mot clé yield identifie les données à renvoyer dans le cadre de la séquence obtenue. Dans les expressions de requête, le mot clé select exécute la même fonction. En plus du mot clé select, F# prend également en charge un certain nombre d’opérateurs de requête qui ressemblent beaucoup aux parties d’une instruction SQL SELECT. Voici un exemple d’expression de requête simple, avec du code qui se connecte à la source OData Northwind.

// Use the OData type provider to create types that can be used to access the Northwind database.
// Add References to FSharp.Data.TypeProviders and System.Data.Services.Client
open Microsoft.FSharp.Data.TypeProviders

type Northwind = ODataService<"http://services.odata.org/Northwind/Northwind.svc">
let db = Northwind.GetDataContext()

// A query expression.
let query1 =
    query {
        for customer in db.Customers do
            select customer
    }

// Print results
query1
|> Seq.iter (fun customer -> printfn "Company: %s Contact: %s" customer.CompanyName customer.ContactName)

Dans l’exemple de code précédent, l’expression de requête est entre accolades. Le sens du code dans l’expression est de renvoyer chaque client de la table Customers de la base de données dans les résultats de requête. Les expressions de requête renvoient un type qui implémente IQueryable<T> et IEnumerable<T>, elles peuvent donc être itérées avec le module Seq comme le montre l’exemple.

Chaque type d’expression de calcul est créé à partir d’une classe de générateur. La classe de générateur de l’expression de calcul de requête est QueryBuilder. Pour plus d’informations, consultez Expressions de calcul et classe QueryBuilder.

Opérateurs de requête

Les opérateurs de requête vous permettent de spécifier les détails de la requête, par exemple, pour placer des critères sur les enregistrements à renvoyer ou spécifier l’ordre de tri des résultats. La source de requête doit prendre en charge l’opérateur de requête. Si vous tentez d’utiliser un opérateur de requête non pris en charge, l’exception System.NotSupportedException est levée.

Seules les expressions qui peuvent être traduites en SQL sont autorisées dans les expressions de requête. Par exemple, aucun appel de fonction n’est autorisé dans les expressions si vous utilisez l’opérateur de requête where.

Le tableau 1 montre les opérateurs de requête disponibles. Par ailleurs, consultez le tableau 2, qui compare les requêtes SQL et les expressions de requête F# équivalentes plus loin dans cette rubrique. Certains opérateurs de requête ne sont pas pris en charge par certains fournisseurs de type. En particulier, le fournisseur de type OData est limité dans les opérateurs de requête qu’il prend en charge en raison de limitations dans OData.

Ce tableau utilise une base de données de la forme suivante :

Diagram that shows a sample database.

Le code dans les tableaux qui suivent utilise également le code de connexion aux bases de données suivant. Les projets doivent ajouter des références aux assemblys System.Data, System.Data.Linq et FSharp.Data.TypeProviders. Le code qui crée cette base de données est ajouté à la fin de cette rubrique.

open System
open Microsoft.FSharp.Data.TypeProviders
open System.Data.Linq.SqlClient
open System.Linq
open Microsoft.FSharp.Linq

type schema = SqlDataConnection< @"Data Source=SERVER\INSTANCE;Initial Catalog=MyDatabase;Integrated Security=SSPI;" >

let db = schema.GetDataContext()

// Needed for some query operator examples:
let data = [ 1; 5; 7; 11; 18; 21]

Tableau 1. Opérateurs de requête

Opérateur Description
contains Détermine si les éléments sélectionnés ont un élément spécifié.

query {
    for student in db.Student do
    select student.Age.Value
    contains 11
}
countRenvoie le nombre d’éléments sélectionnés.

query {
    for student in db.Student do
    select student
    count
}
lastSélectionne le dernier des éléments sélectionnés jusqu’à présent.

query {
    for number in data do
    last
}
lastOrDefaultSélectionne le dernier des éléments sélectionnés jusqu’à présent, ou une valeur par défaut si aucun élément n’est trouvé.

query {
    for number in data do
    where (number < 0)
    lastOrDefault
}
exactlyOneSélectionne le seul élément spécifique sélectionné jusqu’à présent. Si plusieurs éléments sont présents, une exception est levée.

query {
    for student in db.Student do
    where (student.StudentID = 1)
    select student
    exactlyOne
}
exactlyOneOrDefaultSélectionne le seul élément spécifique parmi ceux sélectionnés jusqu’à présent, ou une valeur par défaut si cet élément est introuvable.

query {
    for student in db.Student do
    where (student.StudentID = 1)
    select student
    exactlyOneOrDefault
}
headOrDefaultSélectionne le premier des éléments sélectionnés jusqu’à présent, ou une valeur par défaut si la séquence ne contient aucun élément.

query {
    for student in db.Student do
    select student
    headOrDefault
}
selectProjette chacun des éléments sélectionnés jusqu’à présent.

query {
    for student in db.Student do
    select student
}
whereSélectionne les éléments en fonction d’un prédicat spécifié.

query {
    for student in db.Student do
    where (student.StudentID > 4)
    select student
}
minBySélectionne une valeur pour chaque élément sélectionné jusqu’à présent et renvoie la valeur minimale obtenue.

query {
    for student in db.Student do
    minBy student.StudentID
}
maxBySélectionne une valeur pour chaque élément sélectionné jusqu’à présent et renvoie la valeur maximale obtenue.

query {
    for student in db.Student do
    maxBy student.StudentID
}
groupByRegroupe les éléments sélectionnés jusqu’à présent en fonction d’un sélecteur de clé spécifié.

query {
    for student in db.Student do
    groupBy student.Age into g
    select (g.Key, g.Count())
}
sortByTrie les éléments sélectionnés jusqu’à présent dans l’ordre croissant en utilisant la clé de tri donnée.

query {
    for student in db.Student do
    sortBy student.Name
    select student
}
sortByDescendingTrie les éléments sélectionnés jusqu’à présent dans l’ordre décroissant en utilisant la clé de tri donnée.

query {
    for student in db.Student do
    sortByDescending student.Name
    select student
}
thenByEffectue un tri ultérieur des éléments sélectionnés jusqu’à présent dans l’ordre croissant en utilisant la clé de tri donnée. Cet opérateur peut être utilisé seulement après sortBy, sortByDescending, thenBy ou thenByDescending.

query {
    for student in db.Student do
    where student.Age.HasValue
    sortBy student.Age.Value
    thenBy student.Name
    select student
}
thenByDescendingEffectue un tri ultérieur des éléments sélectionnés jusqu’à présent dans l’ordre décroissant en utilisant la clé de tri donnée. Cet opérateur peut être utilisé seulement après sortBy, sortByDescending, thenBy ou thenByDescending.

query {
    for student in db.Student do
    where student.Age.HasValue
    sortBy student.Age.Value
    thenByDescending student.Name
    select student
}
groupValBySélectionne une valeur pour chaque élément sélectionné jusqu’à présent et regroupe les éléments en fonction de la clé donnée.

query {
    for student in db.Student do
    groupValBy student.Name student.Age into g
    select (g, g.Key, g.Count())
}
joinMet en corrélation deux ensembles de valeurs sélectionnées en fonction de clés correspondantes. Notez que l’ordre des clés autour de du signe = dans une expression de jointure est significatif. Dans toutes les jointures, si la ligne est divisée après le symbole ->, la mise en retrait doit être appliquée au moins jusqu’au mot clé for.

query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    select (student, selection)
}
groupJoinMet en corrélation deux ensembles de valeurs sélectionnées en fonction des clés correspondantes et regroupe les résultats. Notez que l’ordre des clés autour de du signe = dans une expression de jointure est significatif.

query {
    for student in db.Student do
    groupJoin courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID) into g
    for courseSelection in g do
    join course in db.Course
        on (courseSelection.CourseID = course.CourseID)
    select (student.Name, course.CourseName)
}
leftOuterJoinMet en corrélation deux ensembles de valeurs sélectionnées en fonction des clés correspondantes et regroupe les résultats. Si un groupe est vide, un groupe avec une seule valeur par défaut est utilisé à la place. Notez que l’ordre des clés autour de du signe = dans une expression de jointure est significatif.

query {
    for student in db.Student do
    leftOuterJoin selection in db.CourseSelection
        on (student.StudentID = selection.StudentID) into result
    for selection in result.DefaultIfEmpty() do
    select (student, selection)
}
sumByNullableSélectionne une valeur nullable pour chaque élément sélectionné jusqu’à présent et renvoie la somme de ces valeurs. Si un nullable n’a pas de valeur, il est ignoré.

query {
    for student in db.Student do
    sumByNullable student.Age
}
minByNullableSélectionne une valeur nullable pour chaque élément sélectionné jusqu’à présent et renvoie la valeur minimale. Si un nullable n’a pas de valeur, il est ignoré.

query {
    for student in db.Student do
    minByNullable student.Age
}
maxByNullableSélectionne une valeur nullable pour chaque élément sélectionné jusqu’à présent et renvoie la valeur maximale. Si un nullable n’a pas de valeur, il est ignoré.

query {
    for student in db.Student do
    maxByNullable student.Age
}
averageByNullableSélectionne une valeur nullable pour chaque élément sélectionné jusqu’à présent et renvoie la moyenne de ces valeurs. Si un nullable n’a pas de valeur, il est ignoré.

query {
    for student in db.Student do
    averageByNullable (Nullable.float student.Age)
}
averageBySélectionne une valeur pour chaque élément sélectionné jusqu’à présent et renvoie la moyenne de ces valeurs.

query {
    for student in db.Student do
    averageBy (float student.StudentID)
}
distinctSélectionne des éléments distincts parmi les éléments sélectionnés jusqu’à présent.

query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    distinct
}
existsDétermine si un élément sélectionné jusqu’à présent remplit une condition.

query {
    for student in db.Student do
    where
        (query {
            for courseSelection in db.CourseSelection do
            exists (courseSelection.StudentID = student.StudentID) })
    select student
}
findSélectionne le premier élément sélectionné jusqu’à présent qui remplit une condition spécifiée.

query {
    for student in db.Student do
    find (student.Name = "Abercrombie, Kim")
}
allDétermine si tous les éléments sélectionnés jusqu’à présent remplissent une condition.

query {
    for student in db.Student do
    all (SqlMethods.Like(student.Name, "%,%"))
}
headSélectionne le premier des éléments sélectionnés jusqu’à présent.

query {
    for student in db.Student do
    head
}
nthSélectionne l’élément à un index spécifié parmi ceux sélectionnés jusqu’à présent.

query {
    for numbers in data do
    nth 3
}
skipIgnore un nombre spécifié d’éléments sélectionnés jusqu’à présent, puis sélectionne les éléments restants.

query {
    for student in db.Student do
    skip 1
}
skipWhileIgnore des éléments dans une séquence tant que la condition spécifiée a la valeur true, puis sélectionne les éléments restants.

query {
    for number in data do
    skipWhile (number < 3)
    select student
}
sumBySélectionne une valeur pour chaque élément sélectionné jusqu’à présent et renvoie la somme de ces valeurs.

query {
    for student in db.Student do
    sumBy student.StudentID
}
takeSélectionne un nombre spécifié d’éléments contigus parmi ceux sélectionnés jusqu’à présent.

query {
    for student in db.Student do
    select student
    take 2
}
takeWhileSélectionne des éléments dans une séquence tant que la condition spécifiée a la valeur true, puis ignore les éléments restants.

query {
    for number in data do
    takeWhile (number < 10)
}
sortByNullableTrie les éléments sélectionnés jusqu’à présent dans l’ordre croissant en utilisant la clé de tri nullable donnée.

query {
    for student in db.Student do
    sortByNullable student.Age
    select student
}
sortByNullableDescendingTrie les éléments sélectionnés jusqu’à présent dans l’ordre décroissant en utilisant la clé de tri nullable donnée.

query {
    for student in db.Student do
    sortByNullableDescending student.Age
    select student
}
thenByNullableEffectue un tri ultérieur des éléments sélectionnés jusqu’à présent dans l’ordre croissant en utilisant la clé de tri nullable donnée. Cet opérateur peut être utilisé seulement immédiatement après sortBy, sortByDescending, thenBy ou thenByDescending, ou leurs variantes nullables.

query {
    for student in db.Student do
    sortBy student.Name
    thenByNullable student.Age
    select student
}
thenByNullableDescendingEffectue un tri ultérieur des éléments sélectionnés jusqu’à présent dans l’ordre décroissant en utilisant la clé de tri nullable donnée. Cet opérateur peut être utilisé seulement immédiatement après sortBy, sortByDescending, thenBy ou thenByDescending, ou leurs variantes nullables.

query {
    for student in db.Student do
    sortBy student.Name
    thenByNullableDescending student.Age
    select student
}

Comparaison des expressions de requête Transact-SQL et F#

Le tableau suivant montre certaines requêtes Transact-SQL courantes et leurs équivalents en F#. Le code de ce tableau utilise également la même base de données que le tableau précédent et le même code initial pour configurer le fournisseur de type.

Tableau 2. Expressions de requête Transact-SQL et F#

Transact-SQL (ne respecte pas la casse) Expression de requête F# (respecte la casse)
Sélectionne tous les champs de la table.
SELECT * FROM Student

// All students.
query {
    for student in db.Student do
    select student
}
Compte les enregistrements dans une table.
SELECT COUNT( * ) FROM Student

// Count of students.
query {
    for student in db.Student do
    count
}
EXISTS 
SELECT * FROM Student
WHERE EXISTS
  (SELECT * FROM CourseSelection
   WHERE CourseSelection.StudentID = Student.StudentID)

// Find students who have signed up at least one course.
query {
    for student in db.Student do
    where
        (query {
            for courseSelection in db.CourseSelection do
            exists (courseSelection.StudentID = student.StudentID) })
    select student
}
Regroupement
SELECT Student.Age, COUNT( * ) FROM Student
GROUP BY Student.Age

// Group by age and count.
query {
    for n in db.Student do
    groupBy n.Age into g
    select (g.Key, g.Count())
}
// OR
query {
    for n in db.Student do
    groupValBy n.Age n.Age into g
    select (g.Key, g.Count())
}
Regroupement avec une condition.
SELECT Student.Age, COUNT( * )
FROM Student
GROUP BY Student.Age
HAVING student.Age > 10

// Group students by age where age > 10.
query {
    for student in db.Student do
    groupBy student.Age into g
    where (g.Key.HasValue && g.Key.Value > 10)
    select (g.Key, g.Count())
}
Regroupement avec une condition de nombre.
SELECT Student.Age, COUNT( * )
FROM Student
GROUP BY Student.Age
HAVING COUNT( * ) > 1

// Group students by age and count number of students
// at each age with more than 1 student.
query {
    for student in db.Student do
    groupBy student.Age into group
    where (group.Count() > 1)
    select (group.Key, group.Count())
}
Regroupement, comptage et calcul de la somme.
SELECT Student.Age, COUNT( * ), SUM(Student.Age) as total
FROM Student
GROUP BY Student.Age

// Group students by age and sum ages.
query {
    for student in db.Student do
    groupBy student.Age into g
    let total =
        query {
            for student in g do
            sumByNullable student.Age
        }
    select (g.Key, g.Count(), total)
}
Regroupement, comptage et tri par nombre.
SELECT Student.Age, COUNT( * ) as myCount
FROM Student
GROUP BY Student.Age
HAVING COUNT( * ) > 1
ORDER BY COUNT( * ) DESC

// Group students by age, count number of students
// at each age, and display all with count > 1
// in descending order of count.
query {
    for student in db.Student do
    groupBy student.Age into g
    where (g.Count() > 1)
    sortByDescending (g.Count())
    select (g.Key, g.Count())
}
IN un ensemble de valeurs spécifiées
SELECT *
FROM Student
WHERE Student.StudentID IN (1, 2, 5, 10)

// Select students where studentID is one of a given list.
let idQuery =
    query {
        for id in [1; 2; 5; 10] do
        select id
    }
query {
    for student in db.Student do
    where (idQuery.Contains(student.StudentID))
    select student
}
Voir LIKE et TOP.
-- '_e%' matches strings where the second character is 'e'
SELECT TOP 2 * FROM Student
WHERE Student.Name LIKE '_e%'

// Look for students with Name match _e% pattern and take first two.
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "_e%") )
    select student
    take 2
}
LIKE avec des critères spéciaux définis.
-- '[abc]%' matches strings where the first character is
-- 'a', 'b', 'c', 'A', 'B', or 'C'
SELECT * FROM Student
WHERE Student.Name LIKE '[abc]%'

query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "[abc]%") )
    select student
}
LIKE avec un modèle d’exclusion défini.
-- '[^abc]%' matches strings where the first character is
-- not 'a', 'b', 'c', 'A', 'B', or 'C'
SELECT * FROM Student
WHERE Student.Name LIKE '[^abc]%'

// Look for students with name matching [^abc]%% pattern.
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "[^abc]%") )
    select student
}
LIKE sur un champ, mais sélectionne un autre champ.
SELECT StudentID AS ID FROM Student
WHERE Student.Name LIKE '[^abc]%'

query {
    for n in db.Student do
    where (SqlMethods.Like( n.Name, "[^abc]%") )
    select n.StudentID
}
LIKE, avec recherche de sous-chaîne.
SELECT * FROM Student
WHERE Student.Name like '%A%'

// Using Contains as a query filter.
query {
    for student in db.Student do
    where (student.Name.Contains("a"))
    select student
}
JOIN simple avec deux tables.
SELECT * FROM Student
JOIN CourseSelection
ON Student.StudentID = CourseSelection.StudentID

// Join Student and CourseSelection tables.
query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    select (student, selection)
}
LEFT JOIN avec deux tables.
SELECT * FROM Student
LEFT JOIN CourseSelection
ON Student.StudentID = CourseSelection.StudentID

//Left Join Student and CourseSelection tables.
query {
    for student in db.Student do
    leftOuterJoin selection in db.CourseSelection
        on (student.StudentID = selection.StudentID) into result
    for selection in result.DefaultIfEmpty() do
    select (student, selection)
}
JOIN avec COUNT
SELECT COUNT( * ) FROM Student
JOIN CourseSelection
ON Student.StudentID = CourseSelection.StudentID

// Join with count.
query {
    for n in db.Student do
    join e in db.CourseSelection
        on (n.StudentID = e.StudentID)
    count
}
DISTINCT
SELECT DISTINCT StudentID FROM CourseSelection

// Join with distinct.
query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    distinct
}
Nombre distinct.
SELECT DISTINCT COUNT(StudentID) FROM CourseSelection

// Join with distinct and count.
query {
    for n in db.Student do
    join e in db.CourseSelection
        on (n.StudentID = e.StudentID)
    distinct
    count
}
BETWEEN
SELECT * FROM Student
WHERE Student.Age BETWEEN 10 AND 15

// Selecting students with ages between 10 and 15.
query {
    for student in db.Student do
    where (student.Age ?>= 10 && student.Age ?< 15)
    select student
}
OR
SELECT * FROM Student
WHERE Student.Age = 11 OR Student.Age = 12

// Selecting students with age that's either 11 or 12.
query {
    for student in db.Student do
    where (student.Age.Value = 11 &#124;&#124; student.Age.Value = 12)
    select student
}
OR avec tri
SELECT * FROM Student
WHERE Student.Age = 12 OR Student.Age = 13
ORDER BY Student.Age DESC

// Selecting students in a certain age range and sorting.
query {
    for n in db.Student do
    where (n.Age.Value = 12 &#124;&#124; n.Age.Value = 13)
    sortByNullableDescending n.Age
    select n
}
TOP, OR et tri.
SELECT TOP 2 student.Name FROM Student
WHERE Student.Age = 11 OR Student.Age = 12
ORDER BY Student.Name DESC

// Selecting students with certain ages,
// taking account of the possibility of nulls.
query {
    for student in db.Student do
    where
        ((student.Age.HasValue && student.Age.Value = 11) &#124;&#124;
         (student.Age.HasValue && student.Age.Value = 12))
    sortByDescending student.Name
    select student.Name
    take 2
}
UNION de deux requêtes.
SELECT * FROM Student
UNION
SELECT * FROM lastStudent

let query1 =
    query {
        for n in db.Student do
        select (n.Name, n.Age)
    }

let query2 =
    query {
        for n in db.LastStudent do
        select (n.Name, n.Age)
    }

query2.Union (query1)
Intersection de deux requêtes.
SELECT * FROM Student
INTERSECT
SELECT * FROM LastStudent

let query1 =
    query {
        for n in db.Student do
        select (n.Name, n.Age)
    }

let query2 =
    query {
        for n in db.LastStudent do
        select (n.Name, n.Age)
    }

query1.Intersect(query2)
Condition de CASE.
SELECT student.StudentID,
CASE Student.Age
  WHEN -1 THEN 100
  ELSE Student.Age
END,
Student.Age
FROM Student

// Using if statement to alter results for special value.
query {
    for student in db.Student do
    select
        (if student.Age.HasValue && student.Age.Value = -1 then
             (student.StudentID, System.Nullable<int>(100), student.Age)
         else (student.StudentID, student.Age, student.Age))
}
Plusieurs cas.
SELECT Student.StudentID,
CASE Student.Age
  WHEN -1 THEN 100
  WHEN 0 THEN 1000
  ELSE Student.Age
END,
Student.Age
FROM Student

// Using if statement to alter results for special values.
query {
    for student in db.Student do
    select
        (if student.Age.HasValue && student.Age.Value = -1 then
             (student.StudentID, System.Nullable<int>(100), student.Age)
         elif student.Age.HasValue && student.Age.Value = 0 then
             (student.StudentID, System.Nullable<int>(1000), student.Age)
         else (student.StudentID, student.Age, student.Age))
}
Plusieurs tables.
SELECT * FROM Student, Course

// Multiple table select.
query {
    for student in db.Student do
    for course in db.Course do
    select (student, course)
}
Plusieurs jointures.
SELECT Student.Name, Course.CourseName
FROM Student
JOIN CourseSelection
ON CourseSelection.StudentID = Student.StudentID
JOIN Course
ON Course.CourseID = CourseSelection.CourseID

// Multiple joins.
query {
    for student in db.Student do
    join courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID)
    join course in db.Course
        on (courseSelection.CourseID = course.CourseID)
    select (student.Name, course.CourseName)
}
Plusieurs jointures externes gauches.
SELECT Student.Name, Course.CourseName
FROM Student
LEFT OUTER JOIN CourseSelection
ON CourseSelection.StudentID = Student.StudentID
LEFT OUTER JOIN Course
ON Course.CourseID = CourseSelection.CourseID

// Using leftOuterJoin with multiple joins.
query {
    for student in db.Student do
    leftOuterJoin courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID) into g1
    for courseSelection in g1.DefaultIfEmpty() do
    leftOuterJoin course in db.Course
        on (courseSelection.CourseID = course.CourseID) into g2
    for course in g2.DefaultIfEmpty() do
    select (student.Name, course.CourseName)
}

Le code suivant peut être utilisé afin de créer l’exemple de base de données pour ces exemples.

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

USE [master];
GO

IF EXISTS (SELECT * FROM sys.databases WHERE name = 'MyDatabase')
DROP DATABASE MyDatabase;
GO

-- Create the MyDatabase database.
CREATE DATABASE MyDatabase COLLATE SQL_Latin1_General_CP1_CI_AS;
GO

-- Specify a simple recovery model
-- to keep the log growth to a minimum.
ALTER DATABASE MyDatabase
SET RECOVERY SIMPLE;
GO

USE MyDatabase;
GO

CREATE TABLE [dbo].[Course] (
[CourseID]   INT           NOT NULL,
[CourseName] NVARCHAR (50) NOT NULL,
PRIMARY KEY CLUSTERED ([CourseID] ASC)
);

CREATE TABLE [dbo].[Student] (
[StudentID] INT           NOT NULL,
[Name]      NVARCHAR (50) NOT NULL,
[Age]       INT           NULL,
PRIMARY KEY CLUSTERED ([StudentID] ASC)
);

CREATE TABLE [dbo].[CourseSelection] (
[ID]        INT NOT NULL,
[StudentID] INT NOT NULL,
[CourseID]  INT NOT NULL,
PRIMARY KEY CLUSTERED ([ID] ASC),
CONSTRAINT [FK_CourseSelection_ToTable] FOREIGN KEY ([StudentID]) REFERENCES [dbo].[Student] ([StudentID]) ON DELETE NO ACTION ON UPDATE NO ACTION,
CONSTRAINT [FK_CourseSelection_Course_1] FOREIGN KEY ([CourseID]) REFERENCES [dbo].[Course] ([CourseID]) ON DELETE NO ACTION ON UPDATE NO ACTION
);

CREATE TABLE [dbo].[LastStudent] (
[StudentID] INT           NOT NULL,
[Name]      NVARCHAR (50) NOT NULL,
[Age]       INT           NULL,
PRIMARY KEY CLUSTERED ([StudentID] ASC)
);

-- Insert data into the tables.
USE MyDatabase
INSERT INTO Course (CourseID, CourseName)
VALUES(1, 'Algebra I');
INSERT INTO Course (CourseID, CourseName)
VALUES(2, 'Trigonometry');
INSERT INTO Course (CourseID, CourseName)
VALUES(3, 'Algebra II');
INSERT INTO Course (CourseID, CourseName)
VALUES(4, 'History');
INSERT INTO Course (CourseID, CourseName)
VALUES(5, 'English');
INSERT INTO Course (CourseID, CourseName)
VALUES(6, 'French');
INSERT INTO Course (CourseID, CourseName)
VALUES(7, 'Chinese');

INSERT INTO Student (StudentID, Name, Age)
VALUES(1, 'Abercrombie, Kim', 10);
INSERT INTO Student (StudentID, Name, Age)
VALUES(2, 'Abolrous, Hazen', 14);
INSERT INTO Student (StudentID, Name, Age)
VALUES(3, 'Hance, Jim', 12);
INSERT INTO Student (StudentID, Name, Age)
VALUES(4, 'Adams, Terry', 12);
INSERT INTO Student (StudentID, Name, Age)
VALUES(5, 'Hansen, Claus', 11);
INSERT INTO Student (StudentID, Name, Age)
VALUES(6, 'Penor, Lori', 13);
INSERT INTO Student (StudentID, Name, Age)
VALUES(7, 'Perham, Tom', 12);
INSERT INTO Student (StudentID, Name, Age)
VALUES(8, 'Peng, Yun-Feng', NULL);

INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(1, 1, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(2, 1, 3);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(3, 1, 5);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(4, 2, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(5, 2, 5);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(6, 2, 6);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(7, 2, 3);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(8, 3, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(9, 3, 1);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(10, 4, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(11, 4, 5);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(12, 4, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(13, 5, 3);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(14, 5, 2);
INSERT INTO CourseSelection (ID, StudentID, CourseID)
VALUES(15, 7, 3);

Le code suivant contient l’exemple de code qui apparaît dans cette rubrique.

#if INTERACTIVE
#r "FSharp.Data.TypeProviders.dll"
#r "System.Data.dll"
#r "System.Data.Linq.dll"
#endif
open System
open Microsoft.FSharp.Data.TypeProviders
open System.Data.Linq.SqlClient
open System.Linq

type schema = SqlDataConnection<"Data Source=SERVER\INSTANCE;Initial Catalog=MyDatabase;Integrated Security=SSPI;">

let db = schema.GetDataContext()

let data = [1; 5; 7; 11; 18; 21]

type Nullable<'T when 'T : ( new : unit -> 'T) and 'T : struct and 'T :> ValueType > with
    member this.Print() =
        if this.HasValue then this.Value.ToString()
        else "NULL"

printfn "\ncontains query operator"
query {
    for student in db.Student do
    select student.Age.Value
    contains 11
}
|> printfn "Is at least one student age 11? %b"

printfn "\ncount query operator"
query {
    for student in db.Student do
    select student
    count
}
|> printfn "Number of students: %d"

printfn "\nlast query operator."
let num =
    query {
        for number in data do
        sortBy number
        last
    }
printfn "Last number: %d" num

open Microsoft.FSharp.Linq

printfn "\nlastOrDefault query operator."
query {
    for number in data do
    sortBy number
    lastOrDefault
}
|> printfn "lastOrDefault: %d"

printfn "\nexactlyOne query operator."
let student2 =
    query {
        for student in db.Student do
        where (student.StudentID = 1)
        select student
        exactlyOne
    }
printfn "Student with StudentID = 1 is %s" student2.Name

printfn "\nexactlyOneOrDefault query operator."
let student3 =
    query {
        for student in db.Student do
        where (student.StudentID = 1)
        select student
        exactlyOneOrDefault
    }
printfn "Student with StudentID = 1 is %s" student3.Name

printfn "\nheadOrDefault query operator."
let student4 =
    query {
        for student in db.Student do
        select student
        headOrDefault
    }
printfn "head student is %s" student4.Name

printfn "\nselect query operator."
query {
    for student in db.Student do
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.StudentID student.Name)

printfn "\nwhere query operator."
query {
    for student in db.Student do
    where (student.StudentID > 4)
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.StudentID student.Name)

printfn "\nminBy query operator."
let student5 =
    query {
        for student in db.Student do
        minBy student.StudentID
    }

printfn "\nmaxBy query operator."
let student6 =
    query {
        for student in db.Student do
        maxBy student.StudentID
    }

printfn "\ngroupBy query operator."
query {
    for student in db.Student do
    groupBy student.Age into g
    select (g.Key, g.Count())
}
|> Seq.iter (fun (age, count) -> printfn "Age: %s Count at that age: %d" (age.Print()) count)

printfn "\nsortBy query operator."
query {
    for student in db.Student do
    sortBy student.Name
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.StudentID student.Name)

printfn "\nsortByDescending query operator."
query {
    for student in db.Student do
    sortByDescending student.Name
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.StudentID student.Name)

printfn "\nthenBy query operator."
query {
    for student in db.Student do
    where student.Age.HasValue
    sortBy student.Age.Value
    thenBy student.Name
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.Age.Value student.Name)

printfn "\nthenByDescending query operator."
query {
    for student in db.Student do
    where student.Age.HasValue
    sortBy student.Age.Value
    thenByDescending student.Name
    select student
}
|> Seq.iter (fun student -> printfn "StudentID, Name: %d %s" student.Age.Value student.Name)

printfn "\ngroupValBy query operator."
query {
    for student in db.Student do
    groupValBy student.Name student.Age into g
    select (g, g.Key, g.Count())
}
|> Seq.iter (fun (group, age, count) ->
    printfn "Age: %s Count at that age: %d" (age.Print()) count
    group |> Seq.iter (fun name -> printfn "Name: %s" name))

printfn "\n sumByNullable query operator"
query {
    for student in db.Student do
    sumByNullable student.Age
}
|> (fun sum -> printfn "Sum of ages: %s" (sum.Print()))

printfn "\n minByNullable"
query {
    for student in db.Student do
    minByNullable student.Age
}
|> (fun age -> printfn "Minimum age: %s" (age.Print()))

printfn "\n maxByNullable"
query {
    for student in db.Student do
    maxByNullable student.Age
}
|> (fun age -> printfn "Maximum age: %s" (age.Print()))

printfn "\n averageBy"
query {
    for student in db.Student do
    averageBy (float student.StudentID)
}
|> printfn "Average student ID: %f"

printfn "\n averageByNullable"
query {
    for student in db.Student do
    averageByNullable (Nullable.float student.Age)
}
|> (fun avg -> printfn "Average age: %s" (avg.Print()))

printfn "\n find query operator"
query {
    for student in db.Student do
    find (student.Name = "Abercrombie, Kim")
}
|> (fun student -> printfn "Found a match with StudentID = %d" student.StudentID)

printfn "\n all query operator"
query {
    for student in db.Student do
    all (SqlMethods.Like(student.Name, "%,%"))
}
|> printfn "Do all students have a comma in the name? %b"

printfn "\n head query operator"
query {
    for student in db.Student do
    head
}
|> (fun student -> printfn "Found the head student with StudentID = %d" student.StudentID)

printfn "\n nth query operator"
query {
    for numbers in data do
    nth 3
}
|> printfn "Third number is %d"

printfn "\n skip query operator"
query {
    for student in db.Student do
    skip 1
}
|> Seq.iter (fun student -> printfn "StudentID = %d" student.StudentID)

printfn "\n skipWhile query operator"
query {
    for number in data do
    skipWhile (number < 3)
    select number
}
|> Seq.iter (fun number -> printfn "Number = %d" number)

printfn "\n sumBy query operator"
query {
    for student in db.Student do
    sumBy student.StudentID
}
|> printfn "Sum of student IDs: %d"

printfn "\n take query operator"
query {
    for student in db.Student do
    select student
    take 2
}
|> Seq.iter (fun student -> printfn "StudentID = %d" student.StudentID)

printfn "\n takeWhile query operator"
query {
    for number in data do
    takeWhile (number < 10)
}
|> Seq.iter (fun number -> printfn "Number = %d" number)

printfn "\n sortByNullable query operator"
query {
    for student in db.Student do
    sortByNullable student.Age
    select student
}
|> Seq.iter (fun student ->
    printfn "StudentID, Name, Age: %d %s %s" student.StudentID student.Name (student.Age.Print()))

printfn "\n sortByNullableDescending query operator"
query {
    for student in db.Student do
    sortByNullableDescending student.Age
    select student
}
|> Seq.iter (fun student ->
    printfn "StudentID, Name, Age: %d %s %s" student.StudentID student.Name (student.Age.Print()))

printfn "\n thenByNullable query operator"
query {
    for student in db.Student do
    sortBy student.Name
    thenByNullable student.Age
    select student
}
|> Seq.iter (fun student ->
    printfn "StudentID, Name, Age: %d %s %s" student.StudentID student.Name (student.Age.Print()))

printfn "\n thenByNullableDescending query operator"
query {
    for student in db.Student do
    sortBy student.Name
    thenByNullableDescending student.Age
    select student
}
|> Seq.iter (fun student ->
    printfn "StudentID, Name, Age: %d %s %s" student.StudentID student.Name (student.Age.Print()))

printfn "All students: "
query {
    for student in db.Student do
    select student
}
|> Seq.iter (fun student -> printfn "%s %d %s" student.Name student.StudentID (student.Age.Print()))

printfn "\nCount of students: "
query {
    for student in db.Student do
    count
}
|> (fun count -> printfn "Student count: %d" count)

printfn "\nExists."
query {
    for student in db.Student do
    where
        (query {
            for courseSelection in db.CourseSelection do
            exists (courseSelection.StudentID = student.StudentID) })
    select student
}
|> Seq.iter (fun student -> printfn "%A" student.Name)

printfn "\n Group by age and count"
query {
    for n in db.Student do
    groupBy n.Age into g
    select (g.Key, g.Count())
}
|> Seq.iter (fun (age, count) -> printfn "%s %d" (age.Print()) count)

printfn "\n Group value by age."
query {
    for n in db.Student do
    groupValBy n.Age n.Age into g
    select (g.Key, g.Count())
}
|> Seq.iter (fun (age, count) -> printfn "%s %d" (age.Print()) count)

printfn "\nGroup students by age where age > 10."
query {
    for student in db.Student do
    groupBy student.Age into g
    where (g.Key.HasValue && g.Key.Value > 10)
    select (g, g.Key)
}
|> Seq.iter (fun (students, age) ->
    printfn "Age: %s" (age.Value.ToString())
    students
    |> Seq.iter (fun student -> printfn "%s" student.Name))

printfn "\nGroup students by age and print counts of number of students at each age with more than 1 student."
query {
    for student in db.Student do
    groupBy student.Age into group
    where (group.Count() > 1)
    select (group.Key, group.Count())
}
|> Seq.iter (fun (age, ageCount) ->
    printfn "Age: %s Count: %d" (age.Print()) ageCount)

printfn "\nGroup students by age and sum ages."
query {
    for student in db.Student do
    groupBy student.Age into g
    let total = query { for student in g do sumByNullable student.Age }
    select (g.Key, g.Count(), total)
}
|> Seq.iter (fun (age, count, total) ->
    printfn "Age: %d" (age.GetValueOrDefault())
    printfn "Count: %d" count
    printfn "Total years: %s" (total.ToString()))

printfn "\nGroup students by age and count number of students at each age, and display all with count > 1 in descending order of count."
query {
    for student in db.Student do
    groupBy student.Age into g
    where (g.Count() > 1)
    sortByDescending (g.Count())
    select (g.Key, g.Count())
}
|> Seq.iter (fun (age, myCount) ->
    printfn "Age: %s" (age.Print())
    printfn "Count: %d" myCount)

printfn "\n Select students from a set of IDs"
let idList = [1; 2; 5; 10]
let idQuery =
    query { for id in idList do select id }
query {
    for student in db.Student do
    where (idQuery.Contains(student.StudentID))
    select student
}
|> Seq.iter (fun student ->
    printfn "Name: %s" student.Name)

printfn "\nLook for students with Name match _e%% pattern and take first two."
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "_e%") )
    select student
    take 2
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nLook for students with Name matching [abc]%% pattern."
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "[abc]%") )
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nLook for students with name matching [^abc]%% pattern."
query {
    for student in db.Student do
    where (SqlMethods.Like( student.Name, "[^abc]%") )
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nLook for students with name matching [^abc]%% pattern and select ID."
query {
    for n in db.Student do
    where (SqlMethods.Like( n.Name, "[^abc]%") )
    select n.StudentID
}
|> Seq.iter (fun id -> printfn "%d" id)

printfn "\n Using Contains as a query filter."
query {
    for student in db.Student do
    where (student.Name.Contains("a"))
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nSearching for names from a list."
let names = [|"a";"b";"c"|]
query {
    for student in db.Student do
    if names.Contains (student.Name) then select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\nJoin Student and CourseSelection tables."
query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    select (student, selection)
}
|> Seq.iter (fun (student, selection) -> printfn "%d %s %d" student.StudentID student.Name selection.CourseID)

printfn "\nLeft Join Student and CourseSelection tables."
query {
    for student in db.Student do
    leftOuterJoin selection in db.CourseSelection
        on (student.StudentID = selection.StudentID) into result
    for selection in result.DefaultIfEmpty() do
    select (student, selection)
}
|> Seq.iter (fun (student, selection) ->
    let selectionID, studentID, courseID =
        match selection with
        | null -> "NULL", "NULL", "NULL"
        | sel -> (sel.ID.ToString(), sel.StudentID.ToString(), sel.CourseID.ToString())
    printfn "%d %s %d %s %s %s" student.StudentID student.Name (student.Age.GetValueOrDefault()) selectionID studentID courseID)

printfn "\nJoin with count"
query {
    for n in db.Student do
    join e in db.CourseSelection
        on (n.StudentID = e.StudentID)
    count
}
|> printfn "%d"

printfn "\n Join with distinct."
query {
    for student in db.Student do
    join selection in db.CourseSelection
        on (student.StudentID = selection.StudentID)
    distinct
}
|> Seq.iter (fun (student, selection) -> printfn "%s %d" student.Name selection.CourseID)

printfn "\n Join with distinct and count."
query {
    for n in db.Student do
    join e in db.CourseSelection
        on (n.StudentID = e.StudentID)
    distinct
    count
}
|> printfn "%d"

printfn "\n Selecting students with age between 10 and 15."
query {
    for student in db.Student do
    where (student.Age.Value >= 10 && student.Age.Value < 15)
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\n Selecting students with age either 11 or 12."
query {
    for student in db.Student do
    where (student.Age.Value = 11 || student.Age.Value = 12)
    select student
}
|> Seq.iter (fun student -> printfn "%s" student.Name)

printfn "\n Selecting students in a certain age range and sorting."
query {
    for n in db.Student do
    where (n.Age.Value = 12 || n.Age.Value = 13)
    sortByNullableDescending n.Age
    select n
}
|> Seq.iter (fun student -> printfn "%s %s" student.Name (student.Age.Print()))

printfn "\n Selecting students with certain ages, taking account of possibility of nulls."
query {
    for student in db.Student do
    where
        ((student.Age.HasValue && student.Age.Value = 11) ||
         (student.Age.HasValue && student.Age.Value = 12))
    sortByDescending student.Name
    select student.Name
    take 2
}
|> Seq.iter (fun name -> printfn "%s" name)

printfn "\n Union of two queries."
module Queries =
    let query1 = query {
        for n in db.Student do
        select (n.Name, n.Age)
    }

    let query2 = query {
        for n in db.LastStudent do
        select (n.Name, n.Age)
    }

    query2.Union (query1)
    |> Seq.iter (fun (name, age) -> printfn "%s %s" name (age.Print()))

printfn "\n Intersect of two queries."
module Queries2 =
    let query1 = query {
        for n in db.Student do
        select (n.Name, n.Age)
    }

    let query2 = query {
        for n in db.LastStudent do
        select (n.Name, n.Age)
    }

    query1.Intersect(query2)
    |> Seq.iter (fun (name, age) -> printfn "%s %s" name (age.Print()))

printfn "\n Using if statement to alter results for special value."
query {
    for student in db.Student do
    select
        (if student.Age.HasValue && student.Age.Value = -1 then
            (student.StudentID, System.Nullable<int>(100), student.Age)
         else (student.StudentID, student.Age, student.Age))
}
|> Seq.iter (fun (id, value, age) -> printfn "%d %s %s" id (value.Print()) (age.Print()))

printfn "\n Using if statement to alter results special values."
query {
    for student in db.Student do
    select
        (if student.Age.HasValue && student.Age.Value = -1 then
            (student.StudentID, System.Nullable<int>(100), student.Age)
         elif student.Age.HasValue && student.Age.Value = 0 then
            (student.StudentID, System.Nullable<int>(100), student.Age)
         else (student.StudentID, student.Age, student.Age))
}
|> Seq.iter (fun (id, value, age) -> printfn "%d %s %s" id (value.Print()) (age.Print()))

printfn "\n Multiple table select."
query {
    for student in db.Student do
    for course in db.Course do
    select (student, course)
}
|> Seq.iteri (fun index (student, course) ->
    if index = 0 then
        printfn "StudentID Name Age CourseID CourseName"
    printfn "%d %s %s %d %s" student.StudentID student.Name (student.Age.Print()) course.CourseID course.CourseName)

printfn "\nMultiple Joins"
query {
    for student in db.Student do
    join courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID)
    join course in db.Course
        on (courseSelection.CourseID = course.CourseID)
    select (student.Name, course.CourseName)
}
|> Seq.iter (fun (studentName, courseName) -> printfn "%s %s" studentName courseName)

printfn "\nMultiple Left Outer Joins"
query {
    for student in db.Student do
    leftOuterJoin courseSelection in db.CourseSelection
        on (student.StudentID = courseSelection.StudentID) into g1
    for courseSelection in g1.DefaultIfEmpty() do
    leftOuterJoin course in db.Course
        on (courseSelection.CourseID = course.CourseID) into g2
    for course in g2.DefaultIfEmpty() do
    select (student.Name, course.CourseName)
}
|> Seq.iter (fun (studentName, courseName) -> printfn "%s %s" studentName courseName)

Voici la sortie complète quand ce code est exécuté dans F# Interactive.

--> Referenced 'C:\Program Files (x86)\Reference Assemblies\Microsoft\FSharp\3.0\Runtime\v4.0\Type Providers\FSharp.Data.TypeProviders.dll'

--> Referenced 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\System.Data.dll'

--> Referenced 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\System.Data.Linq.dll'

contains query operator
Binding session to 'C:\Users\ghogen\AppData\Local\Temp\tmp5E3C.dll'...
Binding session to 'C:\Users\ghogen\AppData\Local\Temp\tmp611A.dll'...
Is at least one student age 11? true

count query operator
Number of students: 8

last query operator.
Last number: 21

lastOrDefault query operator.
lastOrDefault: 21

exactlyOne query operator.
Student with StudentID = 1 is Abercrombie, Kim

exactlyOneOrDefault query operator.
Student with StudentID = 1 is Abercrombie, Kim

headOrDefault query operator.
head student is Abercrombie, Kim

select query operator.
StudentID, Name: 1 Abercrombie, Kim
StudentID, Name: 2 Abolrous, Hazen
StudentID, Name: 3 Hance, Jim
StudentID, Name: 4 Adams, Terry
StudentID, Name: 5 Hansen, Claus
StudentID, Name: 6 Penor, Lori
StudentID, Name: 7 Perham, Tom
StudentID, Name: 8 Peng, Yun-Feng

where query operator.
StudentID, Name: 5 Hansen, Claus
StudentID, Name: 6 Penor, Lori
StudentID, Name: 7 Perham, Tom
StudentID, Name: 8 Peng, Yun-Feng

minBy query operator.

maxBy query operator.

groupBy query operator.
Age: NULL Count at that age: 1
Age: 10 Count at that age: 1
Age: 11 Count at that age: 1
Age: 12 Count at that age: 3
Age: 13 Count at that age: 1
Age: 14 Count at that age: 1

sortBy query operator.
StudentID, Name: 1 Abercrombie, Kim
StudentID, Name: 2 Abolrous, Hazen
StudentID, Name: 4 Adams, Terry
StudentID, Name: 3 Hance, Jim
StudentID, Name: 5 Hansen, Claus
StudentID, Name: 8 Peng, Yun-Feng
StudentID, Name: 6 Penor, Lori
StudentID, Name: 7 Perham, Tom

sortByDescending query operator.
StudentID, Name: 7 Perham, Tom
StudentID, Name: 6 Penor, Lori
StudentID, Name: 8 Peng, Yun-Feng
StudentID, Name: 5 Hansen, Claus
StudentID, Name: 3 Hance, Jim
StudentID, Name: 4 Adams, Terry
StudentID, Name: 2 Abolrous, Hazen
StudentID, Name: 1 Abercrombie, Kim

thenBy query operator.
StudentID, Name: 10 Abercrombie, Kim
StudentID, Name: 11 Hansen, Claus
StudentID, Name: 12 Adams, Terry
StudentID, Name: 12 Hance, Jim
StudentID, Name: 12 Perham, Tom
StudentID, Name: 13 Penor, Lori
StudentID, Name: 14 Abolrous, Hazen

thenByDescending query operator.
StudentID, Name: 10 Abercrombie, Kim
StudentID, Name: 11 Hansen, Claus
StudentID, Name: 12 Perham, Tom
StudentID, Name: 12 Hance, Jim
StudentID, Name: 12 Adams, Terry
StudentID, Name: 13 Penor, Lori
StudentID, Name: 14 Abolrous, Hazen

groupValBy query operator.
Age: NULL Count at that age: 1
Name: Peng, Yun-Feng
Age: 10 Count at that age: 1
Name: Abercrombie, Kim
Age: 11 Count at that age: 1
Name: Hansen, Claus
Age: 12 Count at that age: 3
Name: Hance, Jim
Name: Adams, Terry
Name: Perham, Tom
Age: 13 Count at that age: 1
Name: Penor, Lori
Age: 14 Count at that age: 1
Name: Abolrous, Hazen

sumByNullable query operator
Sum of ages: 84

minByNullable
Minimum age: 10

maxByNullable
Maximum age: 14

averageBy
Average student ID: 4.500000

averageByNullable
Average age: 12

find query operator
Found a match with StudentID = 1

all query operator
Do all students have a comma in the name? true

head query operator
Found the head student with StudentID = 1

nth query operator
Third number is 11

skip query operator
StudentID = 2
StudentID = 3
StudentID = 4
StudentID = 5
StudentID = 6
StudentID = 7
StudentID = 8

skipWhile query operator
Number = 5
Number = 7
Number = 11
Number = 18
Number = 21

sumBy query operator
Sum of student IDs: 36

take query operator
StudentID = 1
StudentID = 2

takeWhile query operator
Number = 1
Number = 5
Number = 7

sortByNullable query operator
StudentID, Name, Age: 8 Peng, Yun-Feng NULL
StudentID, Name, Age: 1 Abercrombie, Kim 10
StudentID, Name, Age: 5 Hansen, Claus 11
StudentID, Name, Age: 7 Perham, Tom 12
StudentID, Name, Age: 3 Hance, Jim 12
StudentID, Name, Age: 4 Adams, Terry 12
StudentID, Name, Age: 6 Penor, Lori 13
StudentID, Name, Age: 2 Abolrous, Hazen 14

sortByNullableDescending query operator
StudentID, Name, Age: 2 Abolrous, Hazen 14
StudentID, Name, Age: 6 Penor, Lori 13
StudentID, Name, Age: 7 Perham, Tom 12
StudentID, Name, Age: 3 Hance, Jim 12
StudentID, Name, Age: 4 Adams, Terry 12
StudentID, Name, Age: 5 Hansen, Claus 11
StudentID, Name, Age: 1 Abercrombie, Kim 10
StudentID, Name, Age: 8 Peng, Yun-Feng NULL

thenByNullable query operator
StudentID, Name, Age: 1 Abercrombie, Kim 10
StudentID, Name, Age: 2 Abolrous, Hazen 14
StudentID, Name, Age: 4 Adams, Terry 12
StudentID, Name, Age: 3 Hance, Jim 12
StudentID, Name, Age: 5 Hansen, Claus 11
StudentID, Name, Age: 8 Peng, Yun-Feng NULL
StudentID, Name, Age: 6 Penor, Lori 13
StudentID, Name, Age: 7 Perham, Tom 12

thenByNullableDescending query operator
StudentID, Name, Age: 1 Abercrombie, Kim 10
StudentID, Name, Age: 2 Abolrous, Hazen 14
StudentID, Name, Age: 4 Adams, Terry 12
StudentID, Name, Age: 3 Hance, Jim 12
StudentID, Name, Age: 5 Hansen, Claus 11
StudentID, Name, Age: 8 Peng, Yun-Feng NULL
StudentID, Name, Age: 6 Penor, Lori 13
StudentID, Name, Age: 7 Perham, Tom 12
All students:
Abercrombie, Kim 1 10
Abolrous, Hazen 2 14
Hance, Jim 3 12
Adams, Terry 4 12
Hansen, Claus 5 11
Penor, Lori 6 13
Perham, Tom 7 12
Peng, Yun-Feng 8 NULL

Count of students:
Student count: 8

Exists.
"Abercrombie, Kim"
"Abolrous, Hazen"
"Hance, Jim"
"Adams, Terry"
"Hansen, Claus"
"Perham, Tom"

Group by age and count
NULL 1
10 1
11 1
12 3
13 1
14 1

Group value by age.
NULL 1
10 1
11 1
12 3
13 1
14 1

Group students by age where age > 10.
Age: 11
Hansen, Claus
Age: 12
Hance, Jim
Adams, Terry
Perham, Tom
Age: 13
Penor, Lori
Age: 14
Abolrous, Hazen

Group students by age and print counts of number of students at each age with more than 1 student.
Age: 12 Count: 3

Group students by age and sum ages.
Age: 0
Count: 1
Total years:
Age: 10
Count: 1
Total years: 10
Age: 11
Count: 1
Total years: 11
Age: 12
Count: 3
Total years: 36
Age: 13
Count: 1
Total years: 13
Age: 14
Count: 1
Total years: 14

Group students by age and count number of students at each age, and display all with count > 1 in descending order of count.
Age: 12
Count: 3

Select students from a set of IDs
Name: Abercrombie, Kim
Name: Abolrous, Hazen
Name: Hansen, Claus

Look for students with Name match _e% pattern and take first two.
Penor, Lori
Perham, Tom

Look for students with Name matching [abc]% pattern.
Abercrombie, Kim
Abolrous, Hazen
Adams, Terry

Look for students with name matching [^abc]% pattern.
Hance, Jim
Hansen, Claus
Penor, Lori
Perham, Tom
Peng, Yun-Feng

Look for students with name matching [^abc]% pattern and select ID.
3
5
6
7
8

Using Contains as a query filter.
Abercrombie, Kim
Abolrous, Hazen
Hance, Jim
Adams, Terry
Hansen, Claus
Perham, Tom

Searching for names from a list.

Join Student and CourseSelection tables.
2 Abolrous, Hazen 2
3 Hance, Jim 3
5 Hansen, Claus 5
2 Abolrous, Hazen 2
5 Hansen, Claus 5
6 Penor, Lori 6
3 Hance, Jim 3
2 Abolrous, Hazen 2
1 Abercrombie, Kim 1
2 Abolrous, Hazen 2
5 Hansen, Claus 5
2 Abolrous, Hazen 2
3 Hance, Jim 3
2 Abolrous, Hazen 2
3 Hance, Jim 3

Left Join Student and CourseSelection tables.
1 Abercrombie, Kim 10 9 3 1
2 Abolrous, Hazen 14 1 1 2
2 Abolrous, Hazen 14 4 2 2
2 Abolrous, Hazen 14 8 3 2
2 Abolrous, Hazen 14 10 4 2
2 Abolrous, Hazen 14 12 4 2
2 Abolrous, Hazen 14 14 5 2
3 Hance, Jim 12 2 1 3
3 Hance, Jim 12 7 2 3
3 Hance, Jim 12 13 5 3
3 Hance, Jim 12 15 7 3
4 Adams, Terry 12 NULL NULL NULL
5 Hansen, Claus 11 3 1 5
5 Hansen, Claus 11 5 2 5
5 Hansen, Claus 11 11 4 5
6 Penor, Lori 13 6 2 6
7 Perham, Tom 12 NULL NULL NULL
8 Peng, Yun-Feng 0 NULL NULL NULL

Join with count
15

Join with distinct.
Abercrombie, Kim 2
Abercrombie, Kim 3
Abercrombie, Kim 5
Abolrous, Hazen 2
Abolrous, Hazen 5
Abolrous, Hazen 6
Abolrous, Hazen 3
Hance, Jim 2
Hance, Jim 1
Adams, Terry 2
Adams, Terry 5
Adams, Terry 2
Hansen, Claus 3
Hansen, Claus 2
Perham, Tom 3

Join with distinct and count.
15

Selecting students with age between 10 and 15.
Abercrombie, Kim
Abolrous, Hazen
Hance, Jim
Adams, Terry
Hansen, Claus
Penor, Lori
Perham, Tom

Selecting students with age either 11 or 12.
Hance, Jim
Adams, Terry
Hansen, Claus
Perham, Tom

Selecting students in a certain age range and sorting.
Penor, Lori 13
Perham, Tom 12
Hance, Jim 12
Adams, Terry 12

Selecting students with certain ages, taking account of possibility of nulls.
Hance, Jim
Adams, Terry

Union of two queries.
Abercrombie, Kim 10
Abolrous, Hazen 14
Hance, Jim 12
Adams, Terry 12
Hansen, Claus 11
Penor, Lori 13
Perham, Tom 12
Peng, Yun-Feng NULL

Intersect of two queries.

Using if statement to alter results for special value.
1 10 10
2 14 14
3 12 12
4 12 12
5 11 11
6 13 13
7 12 12
8 NULL NULL

Using if statement to alter results special values.
1 10 10
2 14 14
3 12 12
4 12 12
5 11 11
6 13 13
7 12 12
8 NULL NULL

Multiple table select.
StudentID Name Age CourseID CourseName
1 Abercrombie, Kim 10 1 Algebra I
2 Abolrous, Hazen 14 1 Algebra I
3 Hance, Jim 12 1 Algebra I
4 Adams, Terry 12 1 Algebra I
5 Hansen, Claus 11 1 Algebra I
6 Penor, Lori 13 1 Algebra I
7 Perham, Tom 12 1 Algebra I
8 Peng, Yun-Feng NULL 1 Algebra I
1 Abercrombie, Kim 10 2 Trigonometry
2 Abolrous, Hazen 14 2 Trigonometry
3 Hance, Jim 12 2 Trigonometry
4 Adams, Terry 12 2 Trigonometry
5 Hansen, Claus 11 2 Trigonometry
6 Penor, Lori 13 2 Trigonometry
7 Perham, Tom 12 2 Trigonometry
8 Peng, Yun-Feng NULL 2 Trigonometry
1 Abercrombie, Kim 10 3 Algebra II
2 Abolrous, Hazen 14 3 Algebra II
3 Hance, Jim 12 3 Algebra II
4 Adams, Terry 12 3 Algebra II
5 Hansen, Claus 11 3 Algebra II
6 Penor, Lori 13 3 Algebra II
7 Perham, Tom 12 3 Algebra II
8 Peng, Yun-Feng NULL 3 Algebra II
1 Abercrombie, Kim 10 4 History
2 Abolrous, Hazen 14 4 History
3 Hance, Jim 12 4 History
4 Adams, Terry 12 4 History
5 Hansen, Claus 11 4 History
6 Penor, Lori 13 4 History
7 Perham, Tom 12 4 History
8 Peng, Yun-Feng NULL 4 History
1 Abercrombie, Kim 10 5 English
2 Abolrous, Hazen 14 5 English
3 Hance, Jim 12 5 English
4 Adams, Terry 12 5 English
5 Hansen, Claus 11 5 English
6 Penor, Lori 13 5 English
7 Perham, Tom 12 5 English
8 Peng, Yun-Feng NULL 5 English
1 Abercrombie, Kim 10 6 French
2 Abolrous, Hazen 14 6 French
3 Hance, Jim 12 6 French
4 Adams, Terry 12 6 French
5 Hansen, Claus 11 6 French
6 Penor, Lori 13 6 French
7 Perham, Tom 12 6 French
8 Peng, Yun-Feng NULL 6 French
1 Abercrombie, Kim 10 7 Chinese
2 Abolrous, Hazen 14 7 Chinese
3 Hance, Jim 12 7 Chinese
4 Adams, Terry 12 7 Chinese
5 Hansen, Claus 11 7 Chinese
6 Penor, Lori 13 7 Chinese
7 Perham, Tom 12 7 Chinese
8 Peng, Yun-Feng NULL 7 Chinese

Multiple Joins
Abercrombie, Kim Trigonometry
Abercrombie, Kim Algebra II
Abercrombie, Kim English
Abolrous, Hazen Trigonometry
Abolrous, Hazen English
Abolrous, Hazen French
Abolrous, Hazen Algebra II
Hance, Jim Trigonometry
Hance, Jim Algebra I
Adams, Terry Trigonometry
Adams, Terry English
Adams, Terry Trigonometry
Hansen, Claus Algebra II
Hansen, Claus Trigonometry
Perham, Tom Algebra II

Multiple Left Outer Joins
Abercrombie, Kim Trigonometry
Abercrombie, Kim Algebra II
Abercrombie, Kim English
Abolrous, Hazen Trigonometry
Abolrous, Hazen English
Abolrous, Hazen French
Abolrous, Hazen Algebra II
Hance, Jim Trigonometry
Hance, Jim Algebra I
Adams, Terry Trigonometry
Adams, Terry English
Adams, Terry Trigonometry
Hansen, Claus Algebra II
Hansen, Claus Trigonometry
Penor, Lori
Perham, Tom Algebra II
Peng, Yun-Feng

type schema
val db : schema.ServiceTypes.SimpleDataContextTypes.MyDatabase1
val student : System.Data.Linq.Table<schema.ServiceTypes.Student>
val data : int list = [1; 5; 7; 11; 18; 21]
type Nullable<'T
                when 'T : (new : unit ->  'T) and 'T : struct and
                     'T :> System.ValueType> with
  member Print : unit -> string
val num : int = 21
val student2 : schema.ServiceTypes.Student
val student3 : schema.ServiceTypes.Student
val student4 : schema.ServiceTypes.Student
val student5 : int = 1
val student6 : int = 8
val idList : int list = [1; 2; 5; 10]
val idQuery : seq<int>
val names : string [] = [|"a"; "b"; "c"|]
module Queries = begin
  val query1 : System.Linq.IQueryable<string * System.Nullable<int>>
  val query2 : System.Linq.IQueryable<string * System.Nullable<int>>
end
module Queries2 = begin
  val query1 : System.Linq.IQueryable<string * System.Nullable<int>>
  val query2 : System.Linq.IQueryable<string * System.Nullable<int>>
end

Voir aussi