如何在varchar列中求和并在MySQL中显示计数？
为此，将GROUPBY与COUNT（*）一起使用。让我们首先创建一个表-
create table DemoTable ( EmployeeId int NOT NULL AUTO_INCREMENT PRIMARY KEY, EmployeeGender varchar(40) );
使用插入命令在表中插入一些记录-
insert into DemoTable(EmployeeGender) values('MALE');
insert into DemoTable(EmployeeGender) values('FEMALE');
insert into DemoTable(EmployeeGender) values('FEMALE');
insert into DemoTable(EmployeeGender) values('FEMALE');
insert into DemoTable(EmployeeGender) values('MALE');
insert into DemoTable(EmployeeGender) values('MALE');
insert into DemoTable(EmployeeGender) values('MALE');使用select语句显示表中的所有记录-
select *from DemoTable;
这将产生以下输出-
+------------+----------------+ | EmployeeId | EmployeeGender | +------------+----------------+ | 1 | MALE | | 2 | FEMALE | | 3 | FEMALE | | 4 | FEMALE | | 5 | MALE | | 6 | MALE | | 7 | MALE | +------------+----------------+ 7 rows in set (0.00 sec)
以下是对varchar列求和的查询。这将对MALE和FEMALE列值求和，并显示计数-
select EmployeeGender,count(*) from DemoTable group by EmployeeGender;
这将产生以下输出-
+----------------+----------+ | EmployeeGender | count(*) | +----------------+----------+ | MALE | 4 | | FEMALE | 3 | +----------------+----------+ 2 rows in set (0.00 sec)