mysql 常用语法实战总结

单张表通过1个字段清理数据

SELECT
    *
FROM
    fl_mall_member_setting
WHERE
    M_ID IN (
        SELECT
            M_ID
        FROM
            fl_mall_member_setting
        GROUP BY
            M_ID
        HAVING
            count(M_ID) > 1
    )

单张表通过2个字段清理数据

select *
from fl_mall_member_friends a
where exists (select 1
          from (select M_ID, F_ID
                  from fl_mall_member_friends
                 group by M_ID, F_ID
                having count(*) > 1) s
         where s.M_ID = a.M_ID
           and s.F_ID = a.F_ID)

   /**
   * @describe 查询好友列表带分页方法
   * @author chaiyachun
   * @returnType PageBean<SocialMember>
   * @createTime 2018年5月30日下午3:21:28
   */
HashMap<String,Object> paramMap = new HashMap<String,Object>();
       paramMap.put("list", fids);
       paramMap.put("startId", startId);
       PageBean<SocialMember> bean = new PageBean<SocialMember>(socialMemberAndFriendDao.searchSocialFriendByPage(paramMap));
       return bean;



   /**
   * @describe 查询社交会员好友列表带分页
   * @author chaiyachun
   * @returnType List<SocialMember>
   * @createTime 2018年6月1日下午2:23:00
   */
   public List<SocialMember> searchSocialFriendByPage(Map<String,Object> map);


   
   <select id="searchSocialFriendByPage" resultMap="socialMemberResultMap">
       SELECT
       <include refid="socialMemberAll"/>
       FROM FL_SOCIAL_MEMBER
       WHERE
           M_ID IN
           <foreach item="fIds" collection="list" separator="," open="(" close=")" index="">
              #{fIds}
            </foreach>
            AND M_ID >= #{startId}

</select>

******************************mysql 分页优化*****************************************************************

select * from product limit 866613, 20 37.44秒原始方式

SELECT * FROM product WHERE ID > =(select id from product limit 866613, 1) limit 20
查询时间为0.2秒，简直是一个质的飞跃啊，哈哈

另一种写法
SELECT * FROM product a JOIN (select id from product limit 866613, 20) b ON a.ID = b.id

mysql 常用语法实战总结

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