Question

我需要在一个表中并列放置两列，它们具有相同的描述和不同的“外部ID”。输入表如下所示：

+--+-------+-----------+
|ID|OUTERID|DESCRIPTION|
+--+-------+-----------+
|1 |1      |some desc 1|
+--+-------+-----------+
|2 |1      |some desc 2|
+--+-------+-----------+
|3 |1      |some desc 3|
+--+-------+-----------+
|4 |2      |some desc 2|
+--+-------+-----------+
|5 |2      |some desc 3|
+--+-------+-----------+

这是我要从选择中实现的目标：

+-------------+-------------+
|DESCRIPTION_1|DESCRIPTION_2|
+-------------+-------------+
|some desc 1  |NULL         |
+-------------+-------------+
|some desc 2  |some desc 2  |
+-------------+-------------+
|some desc 3  |some desc 3  |
+-------------+-------------+

我尝试了一个简单的JOIN，但是如您所见，我也需要显示不匹配的值。

SELECT a.DESCRIPTION AS DESCRIPTION_1,
       b.DESCRIPTION AS DESCRIPTION_2
  FROM My_Table a
  JOIN My_Table b on a.DESCRIPTION = b.DESCRIPTION
WHERE a.OUTERID = 1
  AND b.OUTERID = 2

Answer 1

您需要assign()并进行条件聚合：

None

Answer 2

如果我理解正确，则可以使用完全外部联接来完成此操作：

SELECT a.DESCRIPTION AS DESCRIPTION_1,
       b.DESCRIPTION AS DESCRIPTION_2
FROM (SELECT a.*
      FROM My_Table a
      WHERE a.OUTERID = 1
     ) a FULL JOIN
     (SELECT b.*
      FROM My_Table b 
      WHERE b.OUTERID = 2
     ) b
     ON a.DESCRIPTION = b.DESCRIPTION;

Answer 3

使用cte ：（不过，我不确定为什么您需要同时显示两列而不是仅标识“重复项”）

表格：

Create Table #tbl
(
ID Int,
OUTERID Int,
DESCRIPTION VarChar(20)
)
Insert Into #tbl Values
(1,1,'some desc 1'),
(2,1,'some desc 2'),
(3,1,'some desc 3'),
(4,2,'some desc 2'),
(5,2,'some desc 3')

CTE

With cte As
(
Select Description, Count(Distinct OuterID) As recs From #tbl
Group By Description
)
Select 
      Case When recs = 2 Or recs = 1 Then Description End As Description_1, 
      Case When recs = 2 Then Description End As Description_2
From cte

比较两个不同列中同一字段的值

3 个答案: