[英]how to join same table in mysql with custom result
I want to join self table to generate with query select. 我想加入自我表生成查询选择。
table A: 表A:
ID || CID || STAT || VAL
...........................
A1 || (-) || 1 || 0
A2 || (-) || 1 || 0
A3 || (-) || 1 || 0
B1 || A1 || 2 || 20
B1 || A2 || 2 || 30
B2 || A1 || 2 || 40
B2 || A1 || 2 || 50
B3 || A1 || 2 || 60
i want to join table A with table A to generate a conditional result. 我想将表A与表A联接以生成条件结果。 can anyone help me to make a result like this? 谁能帮助我取得这样的结果?
ID || CID || VAL
...........................
A1 || B1 || 20
A1 || B2 || 40
A1 || B2 || 50
A1 || B3 || 60
A2 || B1 || 30
A3 || ||
thanks for your attention. 感谢您的关注。
SELECT a.CID,a.ID,a.VAL FROM database.test a LEFT JOIN imt_database.test b ON a.CID = a.ID WHERE a.CID is not null
result : 结果:
A1 B1 20
A2 B1 30
A1 B2 40
A1 B2 50
A1 B3 60
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