mysql删除表中多余的重复记录

删除表中多余的重复记录，重复记录是根据单个字段（MC）来判断，只留有 sysid 最小的记录

-- 删除表中多余的重复记录，重复记录是根据单个字段（MC）来判断，只留有 sysid 最小的记录
DELETE FROM ZD_YPSCCS 
WHERE
    MC IN ( SELECT t.MC FROM ( SELECT MC FROM ZD_YPSCCS GROUP BY MC HAVING count( 1 ) > 1 ) t ) 
    AND sysid NOT IN (
    SELECT
        dt.minsysid
    FROM
    ( SELECT min( sysid ) AS minsysid FROM ZD_YPSCCS GROUP BY MC HAVING count( 1 ) > 1 ) dt 
    )

避免这张表 MC 这个列不再重复，添加 unique 索引。