[Err]1267 - Illegal mix of collations(utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation ‘=’

SELECT * FROM table_a a  where a.id NOT IN (SELECT b.id FROM table_b  b);

先将两个数据表的编码统一，如果table_a的编码为utf8_general_ci，那么将这个表的编码修改下执行以下语句

alert table_a CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;再执行select语句，这样就可以解决编码冲突了；