在SQL Server中优化SELECT查询

Question

我想从SQL Server表中区分两列。我得到这个结果 - 我可以优化这个查询吗？

create TABLE #Temporary_tbl 
(        
    ProductColour VARCHAR(50), 
    ProductSize VARCHAR(20), 
) 

insert into #Temporary_tbl (ProductColour) 
    select distinct productcolour 
    from shoptransfer 

insert into #Temporary_tbl (ProductSize) 
    select distinct ProductSize 
    from shoptransfer 

select * from #Temporary_tbl 

我试试这个：

select distinct ProductColour, null as ProductSize 
from shoptransfer 

union all 

select distinct null as ProductColor, ProductSize 
from shoptransfer 

Answer 1

我认为这个问题是您的期望：我猜要颜色中的一种独特的名单和大小的一个独特的名单，但你希望它们出现在相同的结果表，就像这样：

Colour  Size 
blue  10 
green  12 
orange  14 

即使有蓝色&大小10等之间没有关系这不是数据有很大的表现，因为会发生什么WH有5种颜色，但有100种尺寸。

您可以通过分别选择每个DISTINCT列表和ROW_NUMBER（），然后连接行号来完成此操作。这不是SQL的真正用处，但我可以理解，有时候您想要做这种事情来报告原因。

如

select productSize, productColour 
from ( 
    -- get the colours and a row number 
    select productColour, row_number() over (order by productColour) as rownum 
    from (select distinct productColour from shoptransfer) as c1 
) as colours 
-- full outer join so the row numbers match and you get all the rows from both 
full outer join ( 
    -- get the sizes and a row number 
    select productSize, row_number() over (order by productSize) as rownum 
    from (select distinct productSize from shoptransfer) as s1 
) as sizes 
on colours.rownum = sizes.rownum 

Answer 2

;WITH CTE AS 
(
select ProductColour , null as ProductSize 
from shoptransfer 
GROUP BY ProductColour 

union all 

select null as ProductColor, ProductSize 
from shoptransfer 
GROUP BY ProductSize 
) 
SELECT * FROM CTE 

Answer 3

取决于你如何想在座数据的其他建议也许+ PIVOT

select * from (
    SELECT distinct  
    [ProductColor] as 'tata_column', 'ProductColor' as 'P_TAG'  
    FROM shoptransfer 
union all 
    SELECT distinct 
    [ProductSize] as 'data_colunm' , 'ProductSize' as 'P_TAG' 
    FROM shoptransfer 
    ) A 

我将消除TEMP表运行更快

请注意与大记录集使用“WITH CLAUSE”将放慢，并可能崩溃服务器！