计数MySQL列中每一行的相同值？
要计算每一行的相同值，请使用COUNT（*）和GROUPBY子句。让我们首先创建一个表-
create table DemoTable1818
(
Id int,
Name varchar(20)
);使用插入命令在表中插入一些记录-
insert into DemoTable1818 values(10,'Chris'); insert into DemoTable1818 values(11,'Chris'); insert into DemoTable1818 values(11,'Chris'); insert into DemoTable1818 values(12,'Chris'); insert into DemoTable1818 values(10,'Chris'); insert into DemoTable1818 values(10,'Chris');
使用select语句显示表中的所有记录-
select * from DemoTable1818;
这将产生以下输出-
+------+-------+ | Id | Name | +------+-------+ | 10 | Chris | | 11 | Chris | | 11 | Chris | | 12 | Chris | | 10 | Chris | | 10 | Chris | +------+-------+ 6 rows in set (0.00 sec)
这是查询以计算列中每一行的相同值-
select Id,count(*) as TotalPerId from DemoTable1818 group by Id;
这将产生以下输出-
+------+------------+ | Id | TotalPerId | +------+------------+ | 10 | 3 | | 11 | 2 | | 12 | 1 | +------+------------+ 3 rows in set (0.00 sec)