DATABASE_PRINCIPAL_ID (Transact-SQL)
SQL Server 2008 R2
Returns the ID number of a principal in the current database. For more information about principals, see Principals (Database Engine).
DATABASE_PRINCIPAL_ID can be used in a select list, a WHERE clause, or anywhere an expression is allowed. For more information, see Expressions (Transact-SQL).
A. Retrieving the ID of the current user
The following example returns the database principal ID of the current user.
SELECT DATABASE_PRINCIPAL_ID(); GO
B. Retrieving the ID of a specified database principal
The following example returns the database principal ID for the database role db_owner.
SELECT DATABASE_PRINCIPAL_ID('db_owner');
GO