为MySQL表中的每个值选择最大值？
为此，请结合使用GROUPBY子句MAX()。让我们首先创建一个表-
mysql> create table DemoTable -> ( -> CountryName varchar(20), -> Population int -> );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values('US',560);
mysql> insert into DemoTable values('UK',10090);
mysql> insert into DemoTable values('UK',8794);
mysql> insert into DemoTable values('US',1090);使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
这将产生以下输出-
+-------------+------------+ | CountryName | Population | +-------------+------------+ | US | 560 | | UK | 10090 | | UK | 8794 | | US | 1090 | +-------------+------------+ 4 rows in set (0.00 sec)
以下是查询以选择MySQL表中每个值的最大值-
mysql> select CountryName,max(Population) from DemoTable group by CountryName;
这将产生以下输出-
+-------------+-----------------+ | CountryName | max(Population) | +-------------+-----------------+ | US | 1090 | | UK | 10090 | +-------------+-----------------+ 2 rows in set (0.00 sec)