某一字段分组取最大(小)值所在行的数据

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【mysql技巧】按某一字段分组取最大(小)值所在行的数据

https://blog.csdn.net/zimuxin/article/details/52230662

mysql技巧--按某一字段分组取最大(小)值所在行的数据，这是mysql数据库程序员经常用到的在处理一些报表数据时候可以活用！那么猎微网将总结几种mysql查询最大值 mysql查询最小值的方法！

mysql表图如下

一、按name分组取val最大的值所在行的数据。

    --方法1：  select a.* from tb a where val = (select max(val) from tb where name = a.name) order by a.name  --方法2：  select a.* from tb a where not exists(select 1 from tb where name = a.name and val > a.val)  --方法3：  select a.* from tb a,(select name,max(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name  --方法4：  select a.* from tb a inner join (select name , max(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name  --方法5  select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name  /*  name       val         memo  ---------- ----------- --------------------  a          3           a3:a的第三个值  b          5           b5b5b5b5b5  */

二、按name分组取val最小的值所在行的数据。

--方法1：  
select a.* from tb a where val = (select min(val) from tb where name = a.name) order by a.name  
--方法2：  
select a.* from tb a where not exists(select 1 from tb where name = a.name and val < a.val)  
--方法3：  
select a.* from tb a,(select name,min(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name  
--方法4：  
select a.* from tb a inner join (select name , min(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name  
--方法5  
select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val < a.val) order by a.name  
/*  
name       val         memo  
---------- ----------- --------------------  
a          1           a1--a的第一个值  
b          1           b1--b的第一个值  
*/

这种分组方法好像效率不是很高，我用了10000条记录，5个分组实验一下，要70s的查询时间。但对一般可以满足需求的。

SELECT
        a.payRcvConfirmedID,
        a.StrongRelationID,
        a.balance as orgPayments,
        b.strongRelationType as type,
        e.userID AS payUserId,
        e.realName AS payName,
        e.orgType AS payType,
        f.userID AS recUserId,
        f.realName AS recName,
        f.orgType AS recType
         FROM payrecdb.dt_payrcvconfirmed a
        LEFT JOIN payrecdb.dt_strongrelation b ON a.StrongRelationID=b.strongRelationID
        LEFT JOIN payrecdb.dt_user e ON b.payOrRelUserID = e.userID
        LEFT JOIN payrecdb.dt_user f ON b.rcvOrRelUserID = f.userID
WHERE payRcvConfirmedID = (SELECT max(payRcvConfirmedID) FROM payrecdb.dt_payrcvconfirmed h WHERE h.strongRelationID=a.StrongRelationID) ;