mysql技巧--按某一字段分組取最大(小)值所在行的數據，這是mysql數據庫程序員經常用到的在處理一些報表數據時候可以活用！那麼獵微網將總結幾種mysql查詢最大值 mysql查詢最小值的方法！
mysql表圖如下
具體Php 連接mysql數據庫php代碼我就不寫 下面看select怎麼查詢
一、按name分組取val最大的值所在行的數據。
-
--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的第三個值 -
b 5 b5b5b5b5b5 -
*/
二、按name分組取val最小的值所在行的數據。
-
--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的第一個值 -
b 1 b1--b的第一個值 -
*/
這種分組方法好像效率不是很高，我用了10000條記錄，5個分組實驗一下，要70s的查詢時間。但對一般可以滿足需求的