我写的推荐系统。哈哈。表格什么的自己猜吧

我写的推荐系统。哈哈。表格什么的自己猜吧。 无 INSERT INTO recommend (SELECT ut.userid,it.itemid, NOW() FROM user_tag ut,item_tag it WHERE EXISTS( SELECT it.tagid FROM item_tag it WHERE it.tagid IN (SELECT ut.tagid FROM user_tag ut)))

INSERT INTO recommend (

SELECT ut.userid,it.itemid, NOW() FROM user_tag ut,item_tag it WHERE 
EXISTS
( 

SELECT it.tagid FROM item_tag it WHERE it.tagid IN (SELECT ut.tagid FROM user_tag ut)

)

)