CSDN问答常用SQL问题汇总
2015-08-18 13:36
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一、行列转换
1、原表如图1,现在想实现图2效果,经典的行转列(问题地址:http://ask.csdn.net/questions/200875#answer_122366)
![](https://img-blog.csdn.net/20150818132855559?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center)
实现步骤:
![](https://img-blog.csdn.net/20150818133022554?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center)
![](https://img-blog.csdn.net/20150818133036361?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center)
具体的SQL代码如下:
select A as '运单明细',B as '运单编号', C as '付款方式', D as '运费' from T1;
Declare @sql varchar(8000)
Set @sql = 'Select B as 运单编号'
Select @sql = @sql + ',sum(case C when '''+C+''' then D else 0 end) [付款方式'+C+'的运费合计]'
from (select distinct C from T1) as T --把所有唯一的付款方式的名称都列举出来
Select @sql = @sql+',sum(D) as ''全部运费合计'''
Select @sql = @sql+' from T1 group by B'
Exec (@sql)
2、如下2张表(问题地址:http://ask.csdn.net/questions/197955)Person
![](http://img.ask.csdn.net/upload/201508/04/1438664421_116744.png)
Orders
![](http://img.ask.csdn.net/upload/201508/04/1438664435_617421.png)
要求从上面这两张表中选出以下结果:
![](http://img.ask.csdn.net/upload/201508/04/1438664869_798994.png)
实现步骤:
![](http://img.ask.csdn.net/upload/201508/04/1438667275_623274.png)
![](http://img.ask.csdn.net/upload/201508/04/1438667275_623274.png)
具体SQL代码如下:
1、原表如图1,现在想实现图2效果,经典的行转列(问题地址:http://ask.csdn.net/questions/200875#answer_122366)
实现步骤:
具体的SQL代码如下:
select A as '运单明细',B as '运单编号', C as '付款方式', D as '运费' from T1;
Declare @sql varchar(8000)
Set @sql = 'Select B as 运单编号'
Select @sql = @sql + ',sum(case C when '''+C+''' then D else 0 end) [付款方式'+C+'的运费合计]'
from (select distinct C from T1) as T --把所有唯一的付款方式的名称都列举出来
Select @sql = @sql+',sum(D) as ''全部运费合计'''
Select @sql = @sql+' from T1 group by B'
Exec (@sql)
2、如下2张表(问题地址:http://ask.csdn.net/questions/197955)Person
![](http://img.ask.csdn.net/upload/201508/04/1438664421_116744.png)
Orders
![](http://img.ask.csdn.net/upload/201508/04/1438664435_617421.png)
要求从上面这两张表中选出以下结果:
![](http://img.ask.csdn.net/upload/201508/04/1438664869_798994.png)
实现步骤:
![](http://img.ask.csdn.net/upload/201508/04/1438667275_623274.png)
![](http://img.ask.csdn.net/upload/201508/04/1438667275_623274.png)
具体SQL代码如下:
select t.Id_p,t.LastName,COUNT(OrderNo) as ItemCount from ( select t1.OrderNo,ISNULL(t1.Id_p,t2.Id_p) as Id_p,isnull(t2.LastName,'Unknown') as LastName from Orders t1 full join Person t2 on t1.Id_p = t2.Id_p ) t group by t.Id_p,t.LastName
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