mysql技巧--按某一字段分組取最大(小)值所在行的數(shù)據(jù)，這是mysql數(shù)據(jù)庫(kù)程序員經(jīng)常用到的在處理一些報(bào)表數(shù)據(jù)時(shí)候可以活用！那么獵微網(wǎng)將總結(jié)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(shù)據(jù)庫(kù)php代碼我就不寫 下面看select怎么查詢

一、按name分組取val最大的值所在行的數(shù)據(jù)。

--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(gè)值 b 5 b5b5b5b5b5 */
二、按name分組取val最小的值所在行的數(shù)據(jù)。

--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(gè)值 b 1 b1--b的第一個(gè)值 */
這種分組方法好像效率不是很高，我用了10000條記錄，5個(gè)分組實(shí)驗(yàn)一下，要70s的查詢時(shí)間。但對(duì)一般可以滿足需求的

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