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我有一个USER_ID键,在表A,表B,表C显示出来。MYSQL COUNT函数在多个表
表A
User_id value
1 A
2 B
3 C
表B
User_id value
1 A
1 B
1 C
表C
User_id value
1 A
1 B
0 C
TA是上USER_ID唯一的。我试图用一个查询中的user_id来获取表B和表C中的出现次数。
我想:
SELECT tA.user_id, (SELECT count(*) FROM tB as countB GROUP BY tA.user_id),(SELECT count(*) FROM tC as countC GROUP BY tA.user_id) FROM tA where tA.user_id='1'