Question

让我有一个内连接，产生如下表格

WORKFLOWID  Value
1           One
1           Two
2           Three
2           Four

但我想要的是一条回来的记录

ID    Value1 Value2
1     One    Two
2     Three  Four

我在SQL中有哪些选项可以将内部联接更改为上述行为？

SELECT ws.workflow_id as WorkflowId, sg.unmatched_value as UnmatchedValue
FROM [geo_workflow_step] as ws 
INNER JOIN [geo_workflow] as gw on ws.workflow_id = gw.id
INNER JOIN [geo_super_group] as sg on gw.super_group_id = sg.ID
order by WorkflowId

Answer 1

select t1.workflowid as id,
       min(t1.value) as value1,
       max(t2.value) as value2
from the_table t1
  join the_table t2 
    on t1.workflowid = t2.workflowid
   and t1.value <> t2.value
group by t1.workflowid

这假设表中总是存在两行。如果不是这种情况，你确实会查找PIVOT运算符（搜索它，在SO上有很多问题）

SQLFiddle：http://www.sqlfiddle.com/#!3/97e8b/2

Answer 2

试试这个：

WITH CTE AS
(SELECT *,RN=ROW_NUMBER() OVER(PARTITION BY WORKFLOWID ORDER BY WORKFLOWID) 
 FROM TableName)

SELECT WORKFLOWID,MAX(Value1) as Value1,MAX(Value2) as Value2
FROM
(SELECT WORKFLOWID,
       CASE WHEN RN=1 THEN Value END as Value1,
       CASE WHEN RN=2 THEN Value END as Value2
FROM CTE) T
GROUP BY WORKFLOWID

结果：

WORKFLOWID  VALUE1   VALUE2
1           One      Two
2           Three    Four

请参阅SQL Fiddle中的结果。

Answer 3

DECLARE @t TABLE (Id int,value varchar(20))
INSERT INTO @t
VALUES (1,
        'one'),(1,
                'Two'), (2,
                         'three'),(2,
                                   'four') ;

WITH CTE AS
  ( SELECT DISTINCT t.Id,
                    t.value AS value1,
                    tt.value AS value2,
                    ROW_NUMBER()over(partition BY t.id
                                     ORDER BY t.id)AS RN
   FROM @t t
   INNER JOIN @t tt ON t.Id = tt.Id
   AND t.value <> tt.value )
SELECT ID,
       value1,
       value2
FROM CTE
WHERE rn > 1

从同一行的INNER JOIN获取结果

3 个答案: