SQL Server:列到行 [英] SQL Server : Columns to Rows

问题描述

正在寻找将列转换为行的优雅(或任何)解决方案.

Looking for elegant (or any) solution to convert columns to rows.

这是一个示例:我有一个具有以下架构的表:

Here is an example: I have a table with the following schema:

[ID] [EntityID] [Indicator1] [Indicator2] [Indicator3] ... [Indicator150]

这是我想要的结果:

[ID] [EntityId] [IndicatorName] [IndicatorValue]

结果值为:

1 1 'Indicator1' 'Value of Indicator 1 for entity 1'
2 1 'Indicator2' 'Value of Indicator 2 for entity 1'
3 1 'Indicator3' 'Value of Indicator 3 for entity 1'
4 2 'Indicator1' 'Value of Indicator 1 for entity 2'

等等..

这有意义吗?您对在哪里查看以及如何在 T-SQL 中完成它有什么建议吗?

Does this make sense? Do you have any suggestions on where to look and how to get it done in T-SQL?

推荐答案

您可以使用 UNPIVOT函数将列转换为行:

You can use the UNPIVOT function to convert the columns into rows:

select id, entityId,
  indicatorname,
  indicatorvalue
from yourtable
unpivot
(
  indicatorvalue
  for indicatorname in (Indicator1, Indicator2, Indicator3)
) unpiv;

请注意，您要取消透视的列的数据类型必须相同，因此您可能必须在应用取消透视之前转换数据类型.

Note, the datatypes of the columns you are unpivoting must be the same so you might have to convert the datatypes prior to applying the unpivot.

您也可以使用 CROSS APPLY 和 UNION ALL 来转换列:

You could also use CROSS APPLY with UNION ALL to convert the columns:

select id, entityid,
  indicatorname,
  indicatorvalue
from yourtable
cross apply
(
  select 'Indicator1', Indicator1 union all
  select 'Indicator2', Indicator2 union all
  select 'Indicator3', Indicator3 union all
  select 'Indicator4', Indicator4 
) c (indicatorname, indicatorvalue);

根据您的 SQL Server 版本，您甚至可以将 CROSS APPLY 与 VALUES 子句一起使用:

Depending on your version of SQL Server you could even use CROSS APPLY with the VALUES clause:

select id, entityid,
  indicatorname,
  indicatorvalue
from yourtable
cross apply
(
  values
  ('Indicator1', Indicator1),
  ('Indicator2', Indicator2),
  ('Indicator3', Indicator3),
  ('Indicator4', Indicator4)
) c (indicatorname, indicatorvalue);

最后，如果您有 150 列要逆透视，并且您不想对整个查询进行硬编码，那么您可以使用动态 SQL 生成 sql 语句:

Finally, if you have 150 columns to unpivot and you don't want to hard-code the entire query, then you could generate the sql statement using dynamic SQL:

DECLARE @colsUnpivot AS NVARCHAR(MAX),
   @query  AS NVARCHAR(MAX)

select @colsUnpivot 
  = stuff((select ','+quotename(C.column_name)
           from information_schema.columns as C
           where C.table_name = 'yourtable' and
                 C.column_name like 'Indicator%'
           for xml path('')), 1, 1, '')

set @query 
  = 'select id, entityId,
        indicatorname,
        indicatorvalue
     from yourtable
     unpivot
     (
        indicatorvalue
        for indicatorname in ('+ @colsunpivot +')
     ) u'

exec sp_executesql @query;

这篇关于SQL Server:列到行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！