# MAX (Transact-SQL)MAX (Transact-SQL)

## 語法Syntax

``````-- Aggregation Function Syntax
MAX( [ ALL | DISTINCT ] expression )

-- Analytic Function Syntax
MAX ([ ALL ] expression) OVER ( [ <partition_by_clause> ] [ <order_by_clause> ] )
``````

## 引數Arguments

ALLALL

DISTINCTDISTINCT

expressionexpression

OVER ( [ partition_by_clause ] order_by_clause )OVER ( [ partition_by_clause ] order_by_clause)
partition_by_clause 會將 FROM 子句產生的結果集分割成函數所要套用的分割區。partition_by_clause divides the result set produced by the FROM clause into partitions to which the function is applied. 如未指定，此函數會將查詢結果集的所有資料列視為單一群組。If not specified, the function treats all rows of the query result set as a single group. order_by_clause 可決定執行作業的邏輯順序。order_by_clause determines the logical order in which the operation is performed. order_by_clause 為必要項目。order_by_clause is required. 如需詳細資訊，請參閱 OVER 子句 (Transact-SQL)For more information, see OVER Clause (Transact-SQL).

## RemarksRemarks

MAX 會忽略任何 Null 值。MAX ignores any null values.

MAX 未搭配 OVER 和 ORDER BY 子句使用時，是具決定性函數。MAX is a deterministic function when used without the OVER and ORDER BY clauses. 使用 OVER 和 ORDER BY 子句指定時，則不具決定性。It is nondeterministic when specified with the OVER and ORDER BY clauses. 如需詳細資訊，請參閱 決定性與非決定性函數For more information, see Deterministic and Nondeterministic Functions.

## 範例Examples

### A.A.簡單範例Simple example

``````SELECT MAX(TaxRate)
FROM Sales.SalesTaxRate;
GO
``````

``````-------------------
19.60
Warning, null value eliminated from aggregate.

(1 row(s) affected)
``````

### B.B.使用 OVER 子句Using the OVER clause

``````SELECT DISTINCT Name
, MIN(Rate) OVER (PARTITION BY edh.DepartmentID) AS MinSalary
, MAX(Rate) OVER (PARTITION BY edh.DepartmentID) AS MaxSalary
, AVG(Rate) OVER (PARTITION BY edh.DepartmentID) AS AvgSalary
,COUNT(edh.BusinessEntityID) OVER (PARTITION BY edh.DepartmentID) AS EmployeesPerDept
FROM HumanResources.EmployeePayHistory AS eph
JOIN HumanResources.EmployeeDepartmentHistory AS edh
JOIN HumanResources.Department AS d
ON d.DepartmentID = edh.DepartmentID
WHERE edh.EndDate IS NULL
ORDER BY Name;
``````

``````Name                          MinSalary             MaxSalary             AvgSalary             EmployeesPerDept
----------------------------- --------------------- --------------------- --------------------- ----------------
Document Control              10.25                 17.7885               14.3884               5
Engineering                   32.6923               63.4615               40.1442               6
Executive                     39.06                 125.50                68.3034               4
Facilities and Maintenance    9.25                  24.0385               13.0316               7
Finance                       13.4615               43.2692               23.935                10
Human Resources               13.9423               27.1394               18.0248               6
Information Services          27.4038               50.4808               34.1586               10
Marketing                     13.4615               37.50                 18.4318               11
Production                    6.50                  84.1346               13.5537               195
Production Control            8.62                  24.5192               16.7746               8
Quality Assurance             10.5769               28.8462               15.4647               6
Research and Development      40.8654               50.4808               43.6731               4
Sales                         23.0769               72.1154               29.9719               18
Shipping and Receiving        9.00                  19.2308               10.8718               6
Tool Design                   8.62                  29.8462               23.5054               6

(16 row(s) affected)
``````

### C.C.搭配字元資料使用 MAXUsing MAX with character data

``````SELECT MAX(name) FROM sys.databases WHERE database_id < 5;
``````