我可以在 sql 中订购串联的结果吗？

Question

SQL Server 2008 - 我想将四列连接成分隔值，但我希望它们按字母顺序排列。这可能吗？

**更新：**更多信息... 这将用于每天通过 SSIS 进行的 ETL 作业中大约 700k-1M 行。如果在 SSIS 中有更简单的方法，请告诉我（脚本任务等）。它也可以在存储过程中完成。

还请记住，这些可以为 NULL - 这会给其中一些解决方案带来一些问题。

Answer 1

Unpivot 将列分成行，然后对行进行排序。使用任何你喜欢的row string concatenation technique，比如 FOR XML 技巧：

with cte as (
select *
from (values ('A' ,'C', 'B' ,'D')) as T (c1, c2, c3, c4))
select Value + ',' as [*]
from cte
unpivot (Value for c in (c1, c2, c3, c4)) as u
order by Value
for xml path('')

Answer 2

此要求可能表明您的设计存在问题。如果 4 列中的值在语义上是等效的，您可能会发现将其放入 first normal form 并将重复的列重构到新表中将使此类问题更容易解决。

一个怪物CASE 语句可能会更有效率，但这里有一种方法没有

WITH t AS
(
SELECT 1 as rowid, 'cat' as C1, 'apple' As C2, 
      'bear' AS C3, 'fox' AS C4 UNION ALL
SELECT 2 as rowid, 'B' as C1, 'D' As C2, 'E' AS C3, 'G' AS C4 
)

SELECT rowid,   STUFF((SELECT ',' + C FROM 
(
SELECT C1 AS C FROM t t2 WHERE  t.rowId = t2.rowId
UNION ALL
SELECT C2 AS C FROM t t2 WHERE  t.rowId = t2.rowId
UNION ALL
SELECT C3 AS C FROM t t2 WHERE  t.rowId = t2.rowId
UNION ALL
SELECT C4 AS C FROM t t2 WHERE  t.rowId = t2.rowId
) D
ORDER BY C
        FOR XML PATH('')),1,1,'') X

给予

rowid       X
1           apple,bear,cat,fox
2           B,D,E,G

Answer 3

很复杂，但这会奏效：

   Select Case 
         When a>b And a>c And a>d Then a + ',' +
             Case When b>c And b>d Then b + ',' +
                      Case When c>d Then c Else d End 
                  When c>b And c>d Then c + ',' +
                      Case When b>d Then b Else d End 
                  When d>b And d>c Then d + ',' +
                      Case When b>c Then b Else c End End +
         When b>a And b>c And b>d Then b + ',' +
             Case When a>c And a>d Then a + ',' +
                      Case When c>d Then c Else d End 
                  When c>a And c>d Then c + ',' +
                      Case When a>d Then a Else d End 
                  When d>a And d>c Then a + ',' +
                      Case When a>c Then a Else c End End + ',' +
          etc... 
    End

但我会在代码中而不是在数据库中执行此操作...

编辑：（作为计算列）：

  Alter Table MyTable Add Column SortedABCD As
        Case 
             When a>b And a>c And a>d Then a + ',' +
                 Case When b>c And b>d Then b + ',' +
                          Case When c>d Then c Else d End 
                      When c>b And c>d Then c + ',' +
                          Case When b>d Then b Else d End 
                      When d>b And d>c Then d + ',' +
                          Case When b>c Then b Else c End End +
             When b>a And b>c And b>d Then b + ',' +
                 Case When a>c And a>d Then a + ',' +
                          Case When c>d Then c Else d End 
                      When c>a And c>d Then c + ',' +
                          Case When a>d Then a Else d End 
                      When d>a And d>c Then a + ',' +
                          Case When a>c Then a Else c End End + ',' +
              etc... 
        End