SYSTEM_USER (Transact-SQL)

บทความ
09/03/2024

Applies to: SQL Server Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

Allows a system-supplied value for the current login to be inserted into a table when no default value is specified.

Syntax

SYSTEM_USER

Return Types

nvarchar(128)

Remarks

You can use the SYSTEM_USER function with DEFAULT constraints in the CREATE TABLE and ALTER TABLE statements. You can also use it as any standard function.

If the user name and login name are different, SYSTEM_USER returns the login name.

If the current user is logged in to SQL Server by using Windows Authentication, SYSTEM_USER returns the Windows login identification name in the form: DOMAIN\user_login_name. However, if the current user is logged in to SQL Server by using SQL Server Authentication, SYSTEM_USER returns the SQL Server login identification name, such as WillisJo for a user logged in as WillisJo.

SYSTEM_USER returns the name of the currently executing context. If the EXECUTE AS statement has been used to switch context, SYSTEM_USER returns the name of the impersonated context.

You cannot EXECUTE AS a SYSTEM_USER.

Azure SQL Database: The SYSTEM_USER statement doesn't support execution using an impersonated security context through EXECUTE AS.

Examples

A. Using SYSTEM_USER to return the current system user name

The following example declares a char variable, stores the current value of SYSTEM_USER in the variable, and then prints the value stored in the variable.

DECLARE @sys_usr CHAR(30);  
SET @sys_usr = SYSTEM_USER;  
SELECT 'The current system user is: '+ @sys_usr;  
GO

Here's the result set.

----------------------------------------------------------
The current system user is: WillisJo

(1 row(s) affected)

B. Using SYSTEM_USER with DEFAULT constraints

The following example creates a table with SYSTEM_USER as a DEFAULT constraint for the SRep_tracking_user column.

USE AdventureWorks2022;  
GO  
CREATE TABLE Sales.Sales_Tracking  
(  
    Territory_id INT IDENTITY(2000, 1) NOT NULL,  
    Rep_id INT NOT NULL,  
    Last_sale DATETIME NOT NULL DEFAULT GETDATE(),  
    SRep_tracking_user VARCHAR(30) NOT NULL DEFAULT SYSTEM_USER  
);  
GO  
INSERT Sales.Sales_Tracking (Rep_id)  
VALUES (151);  
INSERT Sales.Sales_Tracking (Rep_id, Last_sale)  
VALUES (293, '19980515');  
INSERT Sales.Sales_Tracking (Rep_id, Last_sale)  
VALUES (27882, '19980620');  
INSERT Sales.Sales_Tracking (Rep_id)  
VALUES (21392);  
INSERT Sales.Sales_Tracking (Rep_id, Last_sale)  
VALUES (24283, '19981130');  
GO

The following query to selects all the information from the Sales_Tracking table:

SELECT * FROM Sales_Tracking ORDER BY Rep_id;  
GO

Here's the result set.

Territory_id Rep_id Last_sale            SRep_tracking_user
-----------  ------ -------------------- ------------------
2000         151    Mar 4 1998 10:36AM   ArvinDak
2001         293    May 15 1998 12:00AM  ArvinDak
2003         21392  Mar 4 1998 10:36AM   ArvinDak
2004         24283  Nov 3 1998 12:00AM   ArvinDak
2002         27882  Jun 20 1998 12:00AM  ArvinDak
 
(5 row(s) affected)

Examples: Azure Synapse Analytics and Analytics Platform System (PDW)

C. Using SYSTEM_USER to return the current system user name

The following example returns the current value of SYSTEM_USER.

SELECT SYSTEM_USER;

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