SQL Server: How to call a UDF, if available?
- by Ian Boyd
Most systems will have a user-defined function (UDF) available. Some will not. i want to use the UDF if it's there:
SELECT
Users.*,
dbo.UserGroupMembershipNames(Users.UserID) AS MemberOfGroupNames
FROM Users
Otherwise fallback to the acceptable alternative
SELECT
Users.*,
(SELECT TOP 1 thing FROM Something
WHERE Something.ID = Users.UserID) AS MemberGroupNames
FROM Users
How do?
My first attempt, using the obvious solution, of course failed:
SELECT
Users.*,
CASE
WHEN (OBJECT_ID('dbo.UserGroupMembershipNames') IS NOT NULL) THEN
dbo.UserGroupMembershipNames(Users.UserID)
ELSE (SELECT TOP 1 thing FROM Something
WHERE Something.ID = Users.UserID)
END AS MemberOfGroupNames
FROM Users
for reasons beyond me
