It's better to write a function, even better a table-valued inline function, and even better a view:

CREATE VIEW view_a as

SELECT a.email, a.membershipexpiry,

Expired = CASE WHEN a.membershipexpiry < GETDATE() THEN 1 ELSE 0 END

FROM dbo.tbl_a a

GO

SELECT * FROM view_a

email membershipexpiry Expired

-------------------- ---------------- -----------

a@a.com 2012-01-01 1

b@a.com 2013-01-01 0

(2 row(s) affected)

It has much better performance than a procedure, but if you must use a procedure you can use the same expression used in a vew.

It would be a procedure with a single command: select.

HTH.