mysql - 连接查询可以对一个查询执行相同的任务

Question

Table A
Table B
Tabls C1, C2 .... Cn : title field

relationship C INNER JOIN B LEFT JOIN A

query 
SELECT C1.title FORM C1 
INNER JOIN B on C1.c_id = B.c_id
LEFT JOIN A on B.b_id = A.b_id

可以合并到一个查询中吗？

Answer 1

我不确定我是否完全理解您的问题，但如果C1，C2，...，Cn都是“并行”表格，那么UNION可能就是特技：

SELECT C1.title AS title FROM C1 INNER JOIN B on C1.c_id = B.c_id LEFT JOIN A on B.b_id = A.b_id
UNION ALL
SELECT C2.title AS title FROM C2 INNER JOIN B on C2.c_id = B.c_id LEFT JOIN A on B.b_id = A.b_id
UNION ALL
...
UNION ALL
SELECT Cn.title AS title FROM Cn INNER JOIN B on Cn.c_id = B.c_id LEFT JOIN A on B.b_id = A.b_id