SUSER_SNAME (Transact-SQL)

server_user_sid

Is the login security identification number. server_user_sid, which is optional, is varbinary(85). server_user_sid can be the security identification number of any SQL Server login or Microsoft Windows user or group. If server_user_sid is not specified, information about the current user is returned. If the parameter contains the word NULL will return NULL.

nvarchar(128)

SUSER_SNAME can be used as a DEFAULT constraint in either ALTER TABLE or CREATE TABLE. SUSER_SNAME can be used in a select list, in a WHERE clause, and anywhere an expression is allowed. SUSER_SNAME must always be followed by parentheses, even if no parameter is specified.

When called without an argument, SUSER_SNAME returns the name of the current security context. When called without an argument within a batch that has switched context by using EXECUTE AS, SUSER_SNAME returns the name of the impersonated context. When called from an impersonated context, ORIGINAL_LOGIN returns the name of the original context.

A. Using SUSER_SNAME

SELECT SUSER_SNAME(0x01);
GO

B. Using SUSER_SNAME with a Windows user security ID

SELECT SUSER_SNAME(0x010500000000000515000000a065cf7e784b9b5fe77c87705a2e0000);
GO

C. Using SUSER_SNAME as a DEFAULT constraint

USE AdventureWorks2012;
GO
CREATE TABLE sname_example
(
login_sname sysname DEFAULT SUSER_SNAME(),
employee_id uniqueidentifier DEFAULT NEWID(),
login_date  datetime DEFAULT GETDATE()
); 
GO
INSERT sname_example DEFAULT VALUES;
GO

D. Calling SUSER_SNAME in combination with EXECUTE AS

SELECT SUSER_SNAME();
GO
EXECUTE AS LOGIN = 'WanidaBenShoof';
SELECT SUSER_SNAME();
REVERT;
GO
SELECT SUSER_SNAME();
GO

Reference

Concepts