sql 分组查询问题

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我是靠谱客的博主生动石头，最近开发中收集的这篇文章主要介绍sql 分组查询问题，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

情景一：
表中数据
name score
aaa 11
aaa 19
bbb 12
bbb 18
ccc 19
ddd 21
期望查询结果如下
name score
aaa 30
bbb 30
ccc 19
ddd 21

复制代码代码如下:

 
---检查表是否存在 
if exists(select * from sysobjects where name='testSum') 
drop table testSum 
go 
---创建表 
create table testSum 
( 
tid int primary key identity(1,1), 
tname varchar(30) null, 
tscor int null 
) 
go 
insert into testSum (tname,tscor) 
select 'aaa',11 
union all 
select 'aaa',19 
union all 
select 'bbb',12 
union all 
select 'bbb',18 
union all 
select 'ccc',19 
union all 
select 'ddd',21 
---查询语句 
select tname ,sum(tscor) from testSum group by tname 
---只查询tscor总和为30的 
select tname ,sum(tscor) from testSum group by tname having sum(tscor)=30 

情景二：
姓名科目分数
张三语文 30
张三数学 50
张三英语 70
李四语文 50
李四数学 80
李四英语 90

期望查询结果：

姓名语文数学英语
张三 30 50 70
李四 50 80 90

复制代码代码如下:

 
---检查表是否存在 
if exists(select * from sysobjects where name='testScore') 
drop table testScore 
go 
---创建表 
create table testScore 
( 
tid int primary key identity(1,1), 
tname varchar(30) null, 
ttype varchar(10) null, 
tscor int null 
) 
go 
---插入数据 
insert into testScore values ('张三','语文',90) 
insert into testScore values ('张三','数学',20) 
insert into testScore values ('张三','英语',50) 
insert into testScore values ('李四','语文',30) 
insert into testScore values ('李四','数学',47) 
insert into testScore values ('李四','英语',78) 
---查询 
select tname as '姓名' , 
max(case ttype when '语文' then tscor else 0 end) '语文', 
max(case ttype when '数学' then tscor else 0 end) '数学', 
max(case ttype when '英语' then tscor else 0 end) '英语' 
from testScore 
group by tname 

情景三：
表:table1
字段：id , name
内容：
----------------
1,aaa
1,bbb
2,ccc
2,ddd
3,eee
3,fff
--------------
希望结果：
---------------------
1 aaa bbb [aaa bbb之间半角空格区分，以下类似]
2 ccc ddd
3 eee fff

复制代码代码如下:

 
f exists(select * from sysobjects where name='test1') 
drop table test1 
go 
create table test1 
( 
tid int primary key identity(1,1), 
tnum int null, 
tname varchar(30) null 
) 
go 
insert into test1 values (1,'aa') 
insert into test1 values (1,'bb') 
insert into test1 values (2,'cc') 
insert into test1 values (2,'dd') 
insert into test1 values (3,'ee') 
insert into test1 values (3,'ff') 
SELECT * FROM ( SELECT DISTINCT tnum FROM test1 
)A 
OUTER APPLY( 
SELECT tname= STUFF(REPLACE(REPLACE( 
( 
SELECT tname FROM test1 N 
WHERE tnum = A.tnum 
FOR XML AUTO 
), '<N tname="', ' '), '"/>', ''), 1, 1, '') 
)N 

情景四：
我需要将表tb中的数据select出来，得到下面第二个表的数据，如何写select语句？
表tb
id a flag class
----------+---------+--------+---------
1 2 1 A
2 2 1 A
3 4 1 A
4 5 2 A
5 3 2 A
6 4 1 A
7 2 1 A
8 3 2 A
9 4 2 A
10 5 3 A
11 5 1 B
12 2 1 B
13 3 1 B
14 4 1 B
15 2 3 B
16 7 3 B
17 3 2 B
18 4 1 B
19 5 1 B
20 2 2 B
21 1 1 B
22 1 1 C
23 2 3 C
24 6 3 C
25 3 2 C
...
需要选取出如下的表，按class列进行分组，a1,a2,a3字段分别为flag=1、2、3时tb表中a字段的求和
选取后
a1 a2 a3 class
-----------+------------+-----------------+--------------
sum(a) sum(a) sum(a) A
sum(a) sum(a) sum(a) B
sum(a) sum(a) sum(a) C
sum(a) sum(a) sum(a) D
sum(a) sum(a) sum(a) E
sum(a) sum(a) sum(a) F
sum(a) sum(a) sum(a) G

复制代码代码如下:

 
---检查表是否存在 
if exists(select * from sysobjects where name='testFlag') 
drop table testFlag 
go 
---创建表 
create table testFlag 
( 
tid int primary key identity(1,1), 
tname varchar(30) null, 
tflag int null, 
tscor int null 
) 
go 
---插入数据 
insert into testFlag (tname,tflag,tscor) 
select 'aaa',1,11 
union all 
select 'aaa',2,19 
union all 
select 'aaa',3,12 
union all 
select 'aaa',1,18 
union all 
select 'aaa',2,19 
union all 
select 'aaa',3,21 
union all 
select 'bbb',1,11 
union all 
select 'bbb',2,19 
union all 
select 'bbb',3,12 
union all 
select 'bbb',1,18 
union all 
select 'bbb',2,19 
union all 
select 'bbb',3,21 
----查询语句 
select distinct tname,(select sum(tscor) from testFlag where tflag=1 and testFlag.tname = t.tname) as 'flag1',(select sum(tscor) from testFlag where tflag=2 and testFlag.tname = t.tname) as 'flag2',(select sum(tscor) from testFlag where tflag=3 and testFlag.tname = t.tname) as 'flag3' from testFlag t group by tname,tflag 