Question

我在sql中有一个包含以下数据的表：

[col1]  [col2]
1       aabb
2       ccdd
3       eeff
4       gghh
1       uuii
2       oopp
3       hhjj
4       lltt
...

col1中的值始终是已知的。如何在表格中对此进行转换，其中第一列的值将是新列，如下所示：

[1]   [2]   [3]   [4]
aabb  ccdd  eeff  gghh
uuii  oopp  hhjj  lltt
...

Answer 1

您需要使用Row_Number和Pivot/Conditional Aggregation

如果col1中的值始终知道

;WITH cte
        AS (SELECT Row_number()OVER(partition BY [col1] ORDER BY [col2]) rn, *
            FROM   Yourtable)
SELECT  [1] = Max(CASE WHEN [col1] = 1 THEN [col2] END),
        [2] = Max(CASE WHEN [col1] = 2 THEN [col2] END),
        [3] = Max(CASE WHEN [col1] = 3 THEN [col2] END),
        [4] = Max(CASE WHEN [col1] = 4 THEN [col2] END)
FROM   cte
GROUP  BY rn

这是一种动态方法

DECLARE @col_list VARCHAR(8000)= '',
        @sql      VARCHAR(8000)

SELECT @col_list = (SELECT DISTINCT ',' + Quotename([col1])
                    FROM   Yourtable
                    FOR xml path (''))

SET @col_list = Stuff(@col_list, 1, 1, '')
SET @sql = 'select ' + @col_list
           + ' from (SELECT Row_number()OVER(partition BY [col1] ORDER BY [col2]) rn, *
                FROM   Yourtable) a pivot (max([col2]) for col1 in ('
           + @col_list + '))pv'

PRINT @sql

EXEC (@sql)

将t-sql列中的表转换为行

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