数据库去重

UPDATE pd_user set id_card=REPLACE(id_card,' ','');

INSERT INTO pd_temp_idcard
SELECT
    MIN(uid) AS minUid,
    id_card
FROM
    pd_user
WHERE
    LENGTH(id_card) > 0
GROUP BY
    id_card
HAVING
    COUNT(*) > 1;
    
DELETE b.* from pd_temp_idcard a, pd_user b where a.id_card=b.id_card and a.minUid != b.uid and LENGTH(b.id_card)>0 ;

UPDATE pd_user SET id_card=null where LENGTH(id_card)=0