USER (Transact-SQL)

บทความ
09/03/2024

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

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

Transact-SQL syntax conventions

Syntax

USER

Return Types

nvarchar(128)

Remarks

USER provides the same functionality as the USER_NAME system function.

Use USER with DEFAULT constraints in either the CREATE TABLE or ALTER TABLE statements, or use as any standard function.

USER always returns the name of the current context. When called after an EXECUTE AS statement, USER returns the name of the impersonated context.

If a Windows principal accesses the database by way of membership in a group, USER returns the name of the Windows principal instead of the name of the group.

Examples

A. Using USER to return the database user name

The following example declares a variable as char, assigns the current value of USER to it, and then prints the variable with a text description.

DECLARE @usr CHAR(30)  
SET @usr = user  
SELECT 'The current user''s database username is: '+ @usr  
GO

Here's the result set.

-----------------------------------------------------------------------  
The current user's database username is: dbo  
 
(1 row(s) affected)

B. Using USER with DEFAULT constraints

The following example creates a table by using USER as a DEFAULT constraint for the salesperson of a sales row.

USE AdventureWorks2022;  
GO  
CREATE TABLE inventory22  
(  
 part_id INT IDENTITY(100, 1) NOT NULL,  
 description VARCHAR(30) NOT NULL,  
 entry_person VARCHAR(30) NOT NULL DEFAULT USER   
)  
GO  
INSERT inventory22 (description)  
VALUES ('Red pencil')  
INSERT inventory22 (description)  
VALUES ('Blue pencil')  
INSERT inventory22 (description)  
VALUES ('Green pencil')  
INSERT inventory22 (description)  
VALUES ('Black pencil')  
INSERT inventory22 (description)  
VALUES ('Yellow pencil')  
GO

This is the query to select all information from the inventory22 table:

SELECT * FROM inventory22 ORDER BY part_id;  
GO

Here is the result set (note the entry-person value):

part_id     description                    entry_person
----------- ------------------------------ -------------------------
100         Red pencil                     dbo
101         Blue pencil                    dbo
102         Green pencil                   dbo
103         Black pencil                   dbo
104         Yellow pencil                  dbo
 
(5 row(s) affected)

C. Using USER in combination with EXECUTE AS

The following example illustrates the behavior of USER when called inside an impersonated session.

SELECT USER;  
GO  
EXECUTE AS USER = 'Mario';  
GO  
SELECT USER;  
GO  
REVERT;  
GO  
SELECT USER;  
GO

Here's the result set.

DBO
Mario
DBO

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