Question

我有一张桌子

主表：tblMain

Phase   Country   City    
AAA     India     Bangalore
AAA     USA       Chicago
ZZZ     USA
ZZZ     UK

SubTable：tblSub

Phase   Country City    Value
AAA     USA     Chicago   3
AAA     USA     NY        6
AAA     UK      London    5
AAA     India   Bangalore 6
AAA     India   Delhi     9
ZZZ     USA     Chicago   7
ZZZ     UK      London    8

预期结果

 Phase   Country   City        Value
  AAA     India     Bangalore   6
  AAA     USA       Chicago     3
  ZZZ     USA                   7 
  ZZZ     UK                    8

我想加入我的Main表，其中包含Phase，Country和City，但条件是对于Phase＆＃34; ZZZ＆＃34;我想只在国家和地区进行加入，而＃34; AAA＆＃34;我想加入ty Country＆amp;市。可以在没有存储过程或临时表的情况下在SQL查询中执行我希望在简单的查询中实现这一点。在此先感谢!!!

Answer 1

SELECT *
FROM This_Table TT 
LEFT JOIN Main_Table MT  ON TT.Countrry = MT.Country  
                        AND TT.Phase = 'ZZZ'
LEFT JOIN Main_Table MT2 ON TT.Countrry = MT2.Country 
                        AND TT.City = MT2.City 
                        AND TT.Phase = 'AAA'

Answer 2

这应该这样做：

WHERE 
    (a.phase = 'ZZZ' AND a.country = b.country)
        OR
    (a.phase = 'AAA' AND a.country = b.country AND a.city = b.city)

如何在SQL中进行条件列连接？

2 个答案: