--- title: "SUSER_SID (Transact-SQL)" description: "SUSER_SID returns the security identification number (SID) for the specified login name." author: VanMSFT ms.author: vanto ms.date: 09/26/2025 ms.service: sql ms.subservice: t-sql ms.topic: reference ms.custom: - ignite-2025 f1_keywords: - "SUSER_SID" - "SUSER_SID_TSQL" helpviewer_keywords: - "logins [SQL Server], users" - "SIDs [SQL Server]" - "security identifiers [SQL Server]" - "users [SQL Server], logins" - "15401 (Database Engine error)" - "IDs [SQL Server], logins" - "identification numbers [SQL Server], logins" - "SUSER_SID function" dev_langs: - "TSQL" monikerRange: "=azuresqldb-current || >=sql-server-2016 || >=sql-server-linux-2017 || =azuresqldb-mi-current || =fabric-sqldb" --- # SUSER_SID (Transact-SQL) [!INCLUDE [SQL Server Azure SQL Database Azure SQL Managed Instance FabricSQLDB](../../includes/applies-to-version/sql-asdb-asdbmi-fabricsqldb.md)] Returns the security identification number (SID) for the specified login name. :::image type="icon" source="../../includes/media/topic-link-icon.svg" border="false"::: [Transact-SQL syntax conventions](../../t-sql/language-elements/transact-sql-syntax-conventions-transact-sql.md) ## Syntax ```syntaxsql SUSER_SID ( [ 'login' ] [ , Param2 ] ) ``` ## Arguments #### '* *login* *' **Applies to**: [!INCLUDE[sql2008-md](../../includes/sql2008-md.md)] and later versions The login name of the user. *login* is **sysname**. *login*, which is optional, can be a [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] login or [!INCLUDE[msCoName](../../includes/msconame-md.md)] Windows user or group. If *login* is not specified, information about the current security context is returned. If the parameter contains `NULL`, `SUSER_SID` returns `NULL`. #### *Param2* **Applies to**: [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and later versions Specifies whether the login name is validated. *Param2* is of type **int** and is optional. When *Param2* is 0, the login name is not validated. When *Param2* is not specified as 0, the Windows login name is verified to be exactly the same as the login name stored in [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)]. ## Return types **varbinary(85)** ## Remarks `SUSER_SID` can be used as a `DEFAULT` constraint in either `ALTER TABLE` or `CREATE TABLE`. `SUSER_SID` can be used in a select list, in a `WHERE` clause, and anywhere an expression is allowed. `SUSER_SID` must always be followed by parentheses, even if no parameter is specified. When called without an argument, `SUSER_SID` returns the SID of the current security context. When called without an argument within a batch that has switched context by using `EXECUTE AS`, `SUSER_SID` returns the SID of the impersonated context. When called from an impersonated context, `SUSER_SID(ORIGINAL_LOGIN())` returns the SID of the original context. When the [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] collation and the Windows collation are different, `SUSER_SID` can fail when [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] and Windows store the login in a different format. For example, if the Windows computer `TestComputer` has the login `User` and [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] stores the login as `TESTCOMPUTER\User`, the lookup of the login `TestComputer\User` might fail to resolve the login name correctly. To skip this validation of the login name, use *Param2*. Differing collations is often a cause of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] error 15401: `Windows NT user or group '%s' not found. Check the name again.` ### Remarks for Azure SQL Database, SQL database in Fabric `SUSER_SID` always return the login SID for the current security context. Use [sys.database_principals](../../relational-databases/system-catalog-views/sys-database-principals-transact-sql.md) to obtain the SID of a different login. The `SUSER_SID` statement does not support execution using an impersonated security context through `EXECUTE AS`. ## Examples ### A. Use SUSER_SID The following example returns the security identification number (SID) for the current security context. ```sql SELECT SUSER_SID(); ``` ### B. Use SUSER_SID with a specific login **Applies to**: [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and later versions The following example returns the security identification number for the [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] `sa` login. ```sql SELECT SUSER_SID('sa'); GO ``` ### C. Use SUSER_SID with a Windows user name **Applies to**: [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and later versions The following example returns the security identification number for the Windows user `London\Workstation1`. ```sql SELECT SUSER_SID('London\Workstation1'); GO ``` ### D. Use SUSER_SID as a DEFAULT constraint The following example uses `SUSER_SID` as a `DEFAULT` constraint in a `CREATE TABLE` statement. ```sql USE AdventureWorks2022; GO CREATE TABLE sid_example ( login_sid VARBINARY(85) DEFAULT SUSER_SID(), login_name VARCHAR(30) DEFAULT SYSTEM_USER, login_dept VARCHAR(10) DEFAULT 'SALES', login_date DATETIME DEFAULT GETDATE() ); GO INSERT sid_example DEFAULT VALUES; GO ``` ### E. Compare the Windows login name to the login name stored in SQL Server **Applies to**: [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and later versions The following example shows how to use *Param2* to obtain the SID from Windows and uses that SID as an input to the `SUSER_SNAME` function. The example provides the login in the format in which it is stored in Windows (`TestComputer\User`), and returns the login in the format in which it is stored in [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] (`TESTCOMPUTER\User`). ```sql SELECT SUSER_SNAME(SUSER_SID('TestComputer\User', 0)); ``` ## Related content - [ORIGINAL_LOGIN (Transact-SQL)](original-login-transact-sql.md) - [CREATE TABLE (Transact-SQL)](../statements/create-table-transact-sql.md) - [binary and varbinary (Transact-SQL)](../data-types/binary-and-varbinary-transact-sql.md) - [System Functions by category for Transact-SQL](../../relational-databases/system-functions/system-functions-category-transact-sql.md)