问题描述
我怎样才能重写这个 t-sql 以避免使用 IN - 而是使用连接?
How can I rewrite this t-sql to avoid using IN - and use joins in stead?
--Members with membership in 2008 but not in 2009, using IN and NOT IN SELECT * FROM @Members WHERE MemberId NOT IN (SELECT MemberId FROM @Memberships WHERE [Year] = 2009) AND MemberId IN (SELECT MemberId FROM @Memberships WHERE [Year] = 2008 )
我想找到在 2008 年有会员资格而在 2009 年没有会员资格的人.以下示例中的正确解决方案是 George 和 Bill
I want to find people with a membership in 2008, who do not have a membership in 2009. The correct solution in the below example is George and Bill
这样的东西...:
--Members with membership in 2008 but not in 2009, using IN and NOT IN SELECT * FROM @Members m INNER JOIN @Memberships msOld ON msOld.MemberId = m.MemberId AND [Year] = 2008 PLAYTHEMOFFKEYBOARDCAT JOIN @... HUh?
完整的模式可以玩.:)
DECLARE @Members TABLE ( MemberId INT, Name VARCHAR(10) ) INSERT INTO @Members VALUES (1, 'Joe') INSERT INTO @Members VALUES (2, 'Mike') INSERT INTO @Members VALUES (3, 'George') INSERT INTO @Members VALUES (4, 'Bill') INSERT INTO @Members VALUES (5, 'Kyle') INSERT INTO @Members VALUES (6, 'Greg') DECLARE @Memberships TABLE ( MembershipId INT, MemberId INT, [Year] INT ) INSERT INTO @Memberships VALUES (1, 1, 2009) INSERT INTO @Memberships VALUES (2, 1, 2007) INSERT INTO @Memberships VALUES (3, 1, 2006) INSERT INTO @Memberships VALUES (4, 2, 2008) INSERT INTO @Memberships VALUES (5, 2, 2009) INSERT INTO @Memberships VALUES (6, 3, 2007) INSERT INTO @Memberships VALUES (7, 3, 2008) INSERT INTO @Memberships VALUES (8, 4, 2008) INSERT INTO @Memberships VALUES (9, 5, 2007) INSERT INTO @Memberships VALUES (10, 5, 2006) INSERT INTO @Memberships VALUES (11, 5, 2005) INSERT INTO @Memberships VALUES (12, 6, 2007) --SELECT * FROM @Members m INNER JOIN @Memberships ms ON m.MemberId = ms.MemberId ORDER BY [Year] --Membership in 2008 SELECT MemberId FROM @Memberships WHERE [Year] = 2008 --Members with no membership in 2009 SELECT * FROM @Members WHERE MemberId NOT IN (SELECT MemberId FROM @Memberships WHERE [Year] = 2009) --Members with membership in 2008 but not in 2009, using IN and NOT IN SELECT * FROM @Members WHERE MemberId NOT IN (SELECT MemberId FROM @Memberships WHERE [Year] = 2009) AND MemberId IN (SELECT MemberId FROM @Memberships WHERE [Year] = 2008 ) --Members with membership in 2008 but not in 2009, using IN and NOT IN SELECT * FROM @Members m INNER JOIN @Memberships msOld ON msOld.MemberId = m.MemberId AND [Year] = 2008
推荐答案
--Members with membership in 2008 but not in 2009, using JOINs SELECT M1.* FROM @Members M1 JOIN @Memberships MS08 ON (M1.MemberId = MS08.MemberId AND MS08.Year = 2008) LEFT JOIN @Memberships MS09 ON (M1.MemberId = MS09.MemberId AND MS09.Year = 2009) WHERE MS09.MemberId IS NULL