帮助SQL查询。 [英] Help with a SQL query.

问题描述

我需要一个查询，其中

a特定列值在特定日期需要，而其他一些列值在两个日期之间是必需的

例如

 选择 t1.col1，t2.col2，SUM（col3）
 来自 my_table1 内部  join  my_table2  on  t1.id = t2.id 
 其中​​ [日期 ]   '  2014-01-01' 和 '  2014-02-11' 
  group   by  t1.col1，t2.col2 

现在，我需要另一个列，即col4，它只需要特定的列date



即如果我要写一个单独的查询，它将是：

 选择 t2.col4 来自 my_table1 内部  join  my_table2  on  t1.id = t2.id 
  where  [日期] = '  2014-02-11 ' 

有没有什么方法可以使用单个查询实现这两个？

任何帮助都将非常感激。

解决方案

你可以用CTE来轻松实现它。

我这样做：

选择t1.col1，t2.col2，SUM（col3），
 case [Date] ='2014-02-11'然后col4 else NULL结束
来自my_table1内部联接my_table2 on t1.id = t2.id 
 where [Date]在'2014-01-01'和'2014-02-11'
 group by t1.col1，t2.col2之间，[Date] ='2014-02-11'然后col4 else NULL结束

I need a query where
a particular column value is required as of a particular date whereas some of the other column values are required as of between two dates
e.g.

select t1.col1, t2.col2, SUM(col3) 
from my_table1 inner join my_table2 on  t1.id = t2.id
where [Date] between '2014-01-01' and '2014-02-11'
group by t1.col1, t2.col2

Now, I need another column i.e. col4 which required only as of a particular date

i.e. if I were to write a separate query it would be :

select t2.col4 from my_table1 inner join my_table2 on  t1.id = t2.id
where [Date] = '2014-02-11'

Is there any way both of these could be achieved using a single query?
Any help would be much appreciated.

解决方案

you can use CTE with this to achieve it easily.

I'd do it like this:

select t1.col1, t2.col2, SUM(col3),
case when [Date] = '2014-02-11' then col4 else NULL end
from my_table1 inner join my_table2 on  t1.id = t2.id
where [Date] between '2014-01-01' and '2014-02-11'
group by t1.col1, t2.col2, case when [Date] = '2014-02-11' then col4 else NULL end

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