【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) ;