没有聚合的透视

Question

我正在尝试pivot without aggregation，并且碰到了一堵墙。

以下是我试图开始工作的示例T-SQL：

declare @optionalFields table (ParentId int, Name nvarchar(50), Value nvarchar(50));
insert into @optionalFields values (1, 'Field1', 'Foo');
insert into @optionalFields values (1, 'Field2', 'Bar');
insert into @optionalFields values (1, 'Field3', '42');
insert into @optionalFields values (2, 'Field1', 'Bar');
insert into @optionalFields values (2, 'Field2', 'Foo');
insert into @optionalFields values (2, 'Field3', '24');

declare @data table (Id int, Name nvarchar(50));
insert into @data values (1, 'Test record 1');
insert into @data values (2, 'Test record 2');

declare @joined table (Id int, Name nvarchar(50), OptionalFieldName nvarchar(50), OptionalFieldValue nvarchar(50));
insert into @joined
select 
     data.Id
    ,data.Name
    ,opt.Name
    ,opt.Value
from @data data
    inner join @optionalFields opt on data.Id = opt.ParentId

declare @cols as nvarchar(max) = 
    stuff((select distinct ',' + quotename(OptionalFieldName) from @joined for xml path(''), type).value('.', 'nvarchar(max)'), 1, 1, '');

select * into #tmp from @joined
-- just to see that it's returning the expected values (it does)
select
     Id
    ,Name
    ,OptionalFieldName
    ,OptionalFieldValue
    ,row_number() over (partition by Id order by Id) RN 
from #tmp -- this is the FROM clause in the below dynamic-sql query

declare @query as nvarchar(max) = '
    select Id, Name, ' + @cols + '
    from (select Id, Name, OptionalFieldName, OptionalFieldValue, row_number() over (partition by Id order by Id) RN from #tmp) src 
    pivot (max(OptionalFieldName) for RN in (' + @cols + ')) pvt';

execute(@query);
drop table #tmp;

SSMS给了我2个错误：

  

  
• Msg 8114，Level 16，State 1，Line 4   将数据类型nvarchar转换为bigint时出错。
  
• Msg 473，Level 16，State 1，Line 4    PIVOT运算符中提供了错误的值“Field1”。
  

“debug”select语句返回：

这篇文章（上面的链接）似乎很有希望，但我似乎无法让它发挥作用。我究竟做错了什么？或者这篇文章是完全错误的，我想要做的是不可能的？

我已经看到了许多类似的SO问题，但要么它们涉及可以“正常工作”聚合的全数字字段，要么它们涉及可以实现为简单连接的已知列 - 我不知道是什么我将要选择OptionalFieldName个值，OptionalFieldValue值是无法聚合的字符串，至少是AFAIK。

Answer 1

我对你为什么试图用row_number()欺骗这一点感到有些困惑。即使您有字符串值，您仍然可以对其进行汇总 - 您只需使用max或min即可获得结果。

我总是建议首先尝试使用硬编码值编写查询，尤其是在尝试使用动态SQL之前使用PIVOT时。我不确定为什么你不能这样写这样的查询：

select Id, Name, Field1, Field2, Field3
from 
(
  select
     Id
    ,Name
    ,OptionalFieldName
    ,OptionalFieldValue
  from #tmp
) d
pivot
(
  max(OptionalFieldValue)
  for OptionalFieldName in (Field1, Field2, Field3)
) piv;

See a Demo

然后，如果你真的需要动态SQL，你只需要编写它：

declare @optionalFields table (ParentId int, Name nvarchar(50), Value nvarchar(50));
insert into @optionalFields values (1, 'Field1', 'Foo');
insert into @optionalFields values (1, 'Field2', 'Bar');
insert into @optionalFields values (1, 'Field3', '42');
insert into @optionalFields values (2, 'Field1', 'Bar');
insert into @optionalFields values (2, 'Field2', 'Foo');
insert into @optionalFields values (2, 'Field3', '24');

declare @data table (Id int, Name nvarchar(50));
insert into @data values (1, 'Test record 1');
insert into @data values (2, 'Test record 2');

declare @joined table (Id int, Name nvarchar(50), OptionalFieldName nvarchar(50), OptionalFieldValue nvarchar(50));
insert into @joined
select 
     data.Id
    ,data.Name
    ,opt.Name
    ,opt.Value
from @data data
    inner join @optionalFields opt on data.Id = opt.ParentId

declare @cols as nvarchar(max);
set @cols = stuff((select distinct ',' + quotename(OptionalFieldName) 
                   from @joined
                   for xml path(''), type).value('.', 'nvarchar(max)'), 1, 1, '');

select * into #tmp from @joined

DECLARE @query  AS NVARCHAR(MAX)

set @query = 'SELECT Id, Name,' + @cols + ' 
            from 
             (
                select Id
                  ,Name
                  ,OptionalFieldName
                  ,OptionalFieldValue
                from #tmp
            ) x
            pivot 
            (
                max(OptionalFieldValue)
                for OptionalFieldName in (' + @cols + ')
            ) p '

execute(@query);

See Demo。两个版本似乎都给出了您所请求的结果。

Answer 2

编辑：此答案仅用于显示完成此旋转的另一种方法。 @bluefeet的答案是最好的解决方案！

希望我明白你的需要：

declare @optionalFields table (ParentId int, Name nvarchar(50), Value nvarchar(50));
insert into @optionalFields values (1, 'Field1', 'Foo');
insert into @optionalFields values (1, 'Field2', 'Bar');
insert into @optionalFields values (1, 'Field3', '42');
insert into @optionalFields values (2, 'Field1', 'Bar');
insert into @optionalFields values (2, 'Field2', 'Foo');
insert into @optionalFields values (2, 'Field3', '24');

declare @data table (Id int, Name nvarchar(50));
insert into @data values (1, 'Test record 1');
insert into @data values (2, 'Test record 2');


select 
     data.Id
    ,data.Name
    ,opt.Name as Name1
    ,opt.Value into #tmp
from @data data
    inner join @optionalFields opt on data.Id = opt.ParentId

declare @cols as nvarchar(max) = 
    stuff((select distinct ',' + quotename(Name1) from #tmp for xml path(''), type).value('.', 'nvarchar(max)'), 1, 1, '');

DECLARE @cols1 as nvarchar(max) = 
    stuff((select distinct +',MAX(CASE WHEN (pvt1.'+quotename(Name1) +' = ros.RN AND pvt1.id = ros.id) THEN ros.Value ELSE NULL END) as '+quotename(Name1)  from #tmp for xml path(''), type).value('.', 'nvarchar(max)'), 1, 1, '');

declare @query as nvarchar(max) = '
 ;WITH cte AS(
 SELECT * FROM #tmp
),

        ros AS (
        SELECT ROW_NUMBER() OVER (partition by Id order by Id) AS [RN],id,Value
        FROM cte),
        pvt1 AS (
    select *
    from (select Id, Name, Name1, row_number() over (partition by Id order by Id) RN 
            from cte) src 
    pivot (max(RN) for Name1 in ('+@cols+')) pvt)

    SELECT pvt1.ID,
            pvt1.Name,
            '+@cols1+'
    FROM pvt1 
    CROSS JOIN ros
    GROUP BY pvt1.ID,
            pvt1.Name'

execute(@query);
drop table #tmp

结果：

ID  Name            Field1  Field2  Field3
1   Test record 1   Foo     Bar     42
2   Test record 2   Bar     Foo     24

如果您添加更多字段，例如insert into @optionalFields values (2, 'Field4', '15');，您将获得：

ID  Name            Field1  Field2  Field3  Field4
1   Test record 1   Foo     Bar     42      NULL
2   Test record 2   Bar     Foo     24      15