Restrict statement

The restrict statement limits the set of table/view entities which are visible to query statements that follow it. For example, in a database that includes two tables (A, B), the application can prevent the rest of the query from accessing B and only "see" a limited form of table A by using a view.

The restrict statement's main scenario is for middle-tier applications that accept queries from users and want to apply a row-level security mechanism over those queries. The middle-tier application can prefix the user's query with a logical model, a set of let statements defining views that restrict the user's access to data, for example ( T | where UserId == "..."). As the last statement being added, it restricts the user's access to the logical model only.

Note

The restrict statement can be used to restrict access to entities in another database or cluster (wildcards are not supported in cluster names).

Syntax

restrict access to (EntitySpecifiers)

Learn more about syntax conventions.

Parameters

Name	Type	Required	Description
EntitySpecifiers	string	✔️	One or more comma-separated entity specifiers. The possible values are: - An identifier defined by a let statement as a tabular view - A table or function reference, similar to one used by a union statement - A pattern defined by a pattern declaration

Note

• All tables, tabular views, or patterns that aren't specified by the restrict statement become "invisible" to the rest of the query.
• Let, set, and tabular statements are strung together/separated by a semicolon, otherwise they won't be considered part of the same query.

Examples

Let statement

The following example uses a let statement appearing before restrict statement.

// Limit access to 'Test' let statement only
let Test = () { print x=1 };
restrict access to (Test);

Tables or functions

The following example uses references to tables or functions that are defined in the database metadata.

// Assuming the database that the query uses has table Table1 and Func1 defined in the metadata, 
// and other database 'DB2' has Table2 defined in the metadata

restrict access to (database().Table1, database().Func1, database('DB2').Table2);

Patterns

The following example uses wildcard patterns that can match multiples of let statements or tables/functions.

let Test1 = () { print x=1 };
let Test2 = () { print y=1 };
restrict access to (*);
// Now access is restricted to Test1, Test2 and no tables/functions are accessible.

// Assuming the database that the query uses has table Table1 and Func1 defined in the metadata.
// Assuming that database 'DB2' has table Table2 and Func2 defined in the metadata
restrict access to (database().*);
// Now access is restricted to all tables/functions of the current database ('DB2' is not accessible).

// Assuming the database that the query uses has table Table1 and Func1 defined in the metadata.
// Assuming that database 'DB2' has table Table2 and Func2 defined in the metadata
restrict access to (database('DB2').*);
// Now access is restricted to all tables/functions of the database 'DB2'

Prevent user from querying other user data

The following example shows how a middle-tier application can prepend a user's query with a logical model that prevents the user from querying any other user's data.

// Assume the database has a single table, UserData,
// with a column called UserID and other columns that hold
// per-user private information.
//
// The middle-tier application generates the following statements.
// Note that "username@domain.com" is something the middle-tier application
// derives per-user as it authenticates the user.
let RestrictedData = view () { Data | where UserID == "username@domain.com" };
restrict access to (RestrictedData);
// The rest of the query is something that the user types.
// This part can only reference RestrictedData; attempting to reference Data
// will fail.
RestrictedData | summarize MonthlySalary=sum(Salary) by Year, Month

// Restricting access to Table1 in the current database (database() called without parameters)
restrict access to (database().Table1);
Table1 | count

// Restricting access to Table1 in the current database and Table2 in database 'DB2'
restrict access to (database().Table1, database('DB2').Table2);
union 
    (Table1),
    (database('DB2').Table2))
| count

// Restricting access to Test statement only
let Test = () { range x from 1 to 10 step 1 };
restrict access to (Test);
Test

// Assume that there is a table called Table1, Table2 in the database
let View1 = view () { Table1 | project Column1 };
let View2 = view () { Table2 | project Column1, Column2 };
restrict access to (View1, View2);

// When those statements appear before the command - the next works
let View1 = view () { Table1 | project Column1 };
let View2 = view () { Table2 | project Column1, Column2 };
restrict access to (View1, View2);
View1 |  count

// When those statements appear before the command - the next access is not allowed
let View1 = view () { Table1 | project Column1 };
let View2 = view () { Table2 | project Column1, Column2 };
restrict access to (View1, View2);
Table1 |  count

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