SUSER_NAME (Transact-SQL)
Applies to: 
SQL Server
Azure SQL Managed Instance
Azure Synapse Analytics (serverless SQL pool only)
Returns the login identification name of the user.
Transact-SQL syntax conventions
Syntax
SUSER_NAME ( [ server_user_id ] )
Note
To view Transact-SQL syntax for SQL Server 2014 and earlier, see Previous versions documentation.
Arguments
server_user_id
The login identification number of the user. server_user_id, which is optional, is int. server_user_id can be the login identification number of any SQL Server login or Windows user or group that has permission to connect to an instance of SQL Server. When server_user_id isn't specified, the login identification name for the current user is returned. If the parameter contains the word NULL, it will return NULL.
Return type
nvarchar(128)
Remarks
SUSER_NAME returns a login name only for a login that has an entry in the syslogins system table.
SUSER_NAME can be used in a select list, in a WHERE clause, and anywhere an expression is allowed. Use parentheses after SUSER_NAME, even if no parameter is specified.
Note
Although the SUSER_NAME function is supported on Azure SQL Database, using EXECUTE AS with SUSER_NAME is not supported on Azure SQL Database.
Examples
The following example returns the login identification name of the user with a login identification number of 1.
SELECT SUSER_NAME(1);