判断某个id是否存在于表中了，如果存在则不插入，不存在则插入 无 INSERT INTO USER (email,ADDTIME) (SELECT 'email','addTime' FROM USER u2 JOIN( SELECT COUNT(*) num FROM USER u1 WHERE u1.id = 87) u3 ON u3.num 1 LIMIT 1)
判断 某个id是否存在于表中了，如果存在则不插入，不存在则插入INSERT INTO USER (email,ADDTIME) (SELECT 'email','addTime' FROM USER u2 JOIN( SELECT COUNT(*) num FROM USER u1 WHERE u1.id = 87) u3 ON u3.num < 1 LIMIT 1)
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