如果没有任何唯一约束，请尝试：
SELECt post_id FROM tags WHERe tag_id = 1 OR tag_id = 3 GROUP BY post_id HAVINg count(DISTINCT tag_id) = 2;
HAVINg如果仅尝试检测两个
tag_id值，请使用此子句：
HAVINg MIN(tag_id) <> MAX(tag_id)
如果post_id和tag_id都具有唯一约束，那么这也应该起作用：
SELECt post_id FROM tags WHERe tag_id = 1 OR tag_id = 3 GROUP BY post_id HAVINg count(*) = 2;
