用SQL group by 去重复，并获取对象

有这样一个表 信息 message_table
id 发送者ID 接受者ID 内容
1 A_ID B_ID XXXX
2 A_ID B_ID YYYY
3 A_ID B_ID ZZZZ
4 C_ID A_ID OOO
5 B_ID A_ID PPPPP
6 B_ID A_ID QQ
7 A_ID D_ID MMMM
8 D_ID A_ID NNNNN
去除重复，将与A_ID有过关系的 B_ID , C_ID ,D_ID的message查出来

看测试数据，好像全部数据都要返回啊 ^_^

SELECt
DISTINCT 内容
FROM
message_table
WHERe
发送者ID = 'A_ID' OR 接受者ID = 'A_ID'

select id from table where times not in(select times from table group by times having count(times)>1); 或者 select id from table where times in(select times from table group by times having count(times)=1); --- 以上，希望对你有所帮助。