解决mysql数据重复问题-只保留一条数据

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<pre name="code" class="html">1.sql语句,原理使用临时表法，效率比较低
delete
  FROM `source`
  WHERE is_deleted=0
          AND (student_id,score_id) IN
      (SELECT f.student_id ,
           f.score_id
      FROM
          (SELECT b.`student_id` AS student_id ,
           b.`score_id` AS score_id
          FROM `source` b
          WHERE b.`is_deleted`=0
          GROUP BY  b.student_id,b.score_id
          HAVING count(*) > 1) f )
              AND id NOT IN
      (SELECT g.id
      FROM
          (SELECT min(c.id) AS id
          FROM `source` c
          WHERE c.`is_deleted`=0
          GROUP BY  c.`student_id`,c.`score_id`
          HAVING count(*)>1) g );

2.临时表法-需要dba协作
1.停服情况下，原表（备份），建一张临时表，将原表的唯一数据拷贝到临时表中，删除源表，更改临时表表名
2.非停服情况下去重，新建一张临时表
insert into temp () values (select distinct * from source)
delete from source where 重复数据 in (select * from temp)
insert into source () values(select * from temp)