SQL Conditional Order By

问题:

I am doing a join on two tables. One is a user's table and the other a list of premium users. I need to have the premium members show up first in my query. However, just because they are in the premium user table doesn't mean they are still a premium member - there is an IsActive field that also needs to be checked.

So basically I need to return the results in the following order:

• Active Premium Users
• Regular and Inactive Premium Users

Right now I have it as the following:

SELECT Users.MemberId, PremiumUsers.IsActive FROM Users
LEFT JOIN PremiumUsers ON PremiumUsers.UserId = Users.Id
ORDER BY PremiumUsers.IsActive DESC

The problem with this is that it places non-active premium members above non-premium members.

(I'm using MS SQL Server 2005 for this)

回答1:

ORDER BY COALESCE(PremiumUsers.IsActive, 0) DESC

That will group the NULLs with not-actives.

回答2:

try ORDER BY CASE

ORDER BY CASE
    WHEN PremiumUsers.IsActive = 1 THEN 1
    WHEN PremiumUsers.UserId IS NULL THEN 2
    ELSE 3
END