推荐系统核心部分

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 EXISTS (SELECT ut.tagid = it.tagid FROM user_tag ut,item_tag it)

)

)

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