T-SQL，用於更改一個表中的數據並插入到另一個表中

Question

我的基本表是這樣的：

ColumnA|ColumnB
---------------
   A   |  C1
   A   |  C2
   A   |  C3
   B   |  C1
   B   |  C3
   C   |  C4

我想從基表中讀取記錄並將其寫入下表：

ColumnA | C1 | C2 | C3 | C4
----------------------------
   A    | Y  |  Y | Y  | N
   B    | Y  |  N | Y  | N
   C    | N  |  N | N  | Y

我不想使用光標，但是我不知道這是否可行。

謝謝

Answer 1

看一下PIVOT命令。 從那里可以執行INSERT INTO ... SELECT ...

SELECT ColumnA, [C1], [C2], [C3], [C4]
 FROM (SELECT * FROM table) t 
PIVOT
(
 Count(ColumnB)
 FOR ColumnB IN ([C1], [C2], [C3], [C4])
) As Pvt 

Answer 2

一種（通常是快速的）方式是group by ：

insert  NewTable (ColumnA, C1, C2, C3, C4)
select  ColumnA
,       IsNull(max(case when ColumnB = 'C1' then 'Y' end), 'N')
,       IsNull(max(case when ColumnB = 'C2' then 'Y' end), 'N')
,       IsNull(max(case when ColumnB = 'C3' then 'Y' end), 'N')
,       IsNull(max(case when ColumnB = 'C4' then 'Y' end), 'N')
from    OldTable
group by
        ColumnA

另一種方法是子查詢，例如：

insert  NewTable (ColumnA, C1, C2, C3, C4)
select  src.ColumnA
,       case when exists (select * from OldTable ot 
                          where ot.ColumnA = src.ColumnA and ot.ColumnB = 'C1') 
                  then 'Y' else 'N' end
,       case when exists (select * from OldTable ot 
                          where ot.ColumnA = src.ColumnA and ot.ColumnB = 'C2') 
                  then 'Y' else 'N' end
,       case when exists (select * from OldTable ot 
                          where ot.ColumnA = src.ColumnA and ot.ColumnB = 'C3') 
                  then 'Y' else 'N' end
,       case when exists (select * from OldTable ot 
                          where ot.ColumnA = src.ColumnA and ot.ColumnB = 'C4') 
                  then 'Y' else 'N' end
from    (
        select  distinct ColumnA
        from    OldTable
        ) src

或者，改編自克里斯潛水員的答案，與pivot ：

select  ColumnA
,       case when C1 > 0 then 'Y' else 'N' end C1
,       case when C2 > 0 then 'Y' else 'N' end C2
,       case when C3 > 0 then 'Y' else 'N' end C3
,       case when C4 > 0 then 'Y' else 'N' end C4
from    OldTable src
pivot   (
        count(ColumnB)
        for ColumnB IN ([C1], [C2], [C3], [C4])
        ) pvt

Answer 3

假設您可以選擇所需的信息，則可以將插入內容作為選擇的結果。