有一个学生记录的表student，形式如下：  name  class

sex  1

a 男 2 b 女 3 c 男 4 a 男 5 a 女 6 a 男 ……  现要统计每个班级的男女人数，结果如下：  class  男 女 a 3 1

b 0

1  c 1

0  用一句select语句实现

SQL:

create table student

(

sID int identity(1,1) primary key not

null,

sname varchar(8) not null,

class int not null,

sex char(2) not null

)

go

insert into student values('admin',1,'男')

insert into student values('111',1,'女')

insert into student values('张三',2,'男')

insert into student values('hui',2,'女')

insert into student values('李四',2,'男')

insert into student values('xin',3,'女')

insert into student values('xin',3,'女')

go

select * from student

select class , sum(case sex when '男' then 1

else 0 end ) as '男' ,女=sum(case sex when '女' then 1 else 0

end)

from student group by class

ORACLE:

create table student

(

sID number primary key not null,

sname varchar2(8) not null,

class int not null,

sex char(2) not null

)

insert into student values(seq_id.nextval,'admin',1,'男');

insert into student values(seq_id.nextval,'111',1,'女');

insert into student values(seq_id.nextval,'张三',2,'男');

insert into student values(seq_id.nextval,'hui',2,'女');

insert into student values(seq_id.nextval,'李四',2,'男');

insert into student values(seq_id.nextval,'xin',3,'女');

insert into student values(seq_id.nextval,'xin',3,'女');

select * from student;

select class,sum(decode(sex,'男',1,0))

男,sum(decode(sex,'女',1,0))

女 from student group by class;

select class,sum(F),sum(M)

from ( select class,count(*) F, 0 M

from student where sex='男'

group by class union select class,0 F ,count(*) M

from student where sex='女'

group by class ) group by class

扩展:一个班级只有一个男生很女生,在一条记录上分别显示姓名

insert into student values('admin',1,'男')

insert into student values('111',1,'女')

insert into student values('张三',2,'男')

insert into student values('hui',2,'女')

预期结果

class 男 女 1 admin 111

2 张三 hui

SQL:

①:

select a.class,a.sname as '男',b.sname as

'女'

from student a inner join student b on a.class=b.class

where a.sex='男' and b.sex='女'

②:

select a.class,a.sname as '男' ,b.sname as

'女' from

(select * from student where sex='男')a,

(select * from student where sex='女')b

where a.class=b.class