Returns the login identification name of the user.
In SQL Server version 7.0, the security identification number (SID) replaced the server user identification number (SUID).
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, and must always be followed by parentheses, even if no parameter is specified.
The following example returns the login identification name of the user with a login identification number of 1.