大多数系统都有一个用户定义的函数(UDF)可用。有些人不会。我想使用UDF,如果它的存在:SQL Server:如何调用UDF(如果可用)?
SELECT
Users.*,
dbo.UserGroupMembershipNames(Users.UserID) AS MemberOfGroupNames
FROM Users
否则退回到可接受的替代
SELECT
Users.*,
(SELECT TOP 1 thing FROM Something
WHERE Something.ID = Users.UserID) AS MemberGroupNames
FROM Users
怎么办?
我第一次尝试,使用明显的解决方案,当然失败:
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
超出我的原因
....但只能有一个。较低的GearScore的凯德得到它。 – 2010-04-02 15:47:31