没有聚合的透视

Question

我正在尝试 pivot without aggregation，并且运行有点撞墙。

这是示例 T-SQL 我正在尝试开始工作：

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 出现 2 个错误：

Msg 8114, Level 16, State 1, Line 4 Error converting data type nvarchar to bigint.

Msg 473, Level 16, State 1, Line 4 The incorrect value "Field1" is supplied in the PIVOT operator.

"debug" select 语句返回：

这篇文章（link 上面）看起来很有前途，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，我想做的是不可能的？

我见过许多类似的 SO 问题，但它们要么涉及可以 "just work" 进行聚合的全数字字段，要么涉及可以作为简单连接实现的已知列 - 我不知道我不知道我要 selecting 什么 OptionalFieldName 值，OptionalFieldValue 值是根本无法聚合的字符串，至少 AFAIK。

Answer 1

编辑：这个答案在这里只是为了展示另一种完成这种旋转的方法。 @bluefeet 的回答是最好的解决方案！

希望我明白你需要什么：

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，如 insert into @optionalFields values (2, 'Field4', '15');，您将得到：

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

Answer 2

我有点不明白你为什么要用 row_number() 来欺骗它。即使你有字符串值，你仍然可以聚合它——你只需要使用 max 或 min 来获得结果。

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.

那如果你真的需要动态的SQL，你就这么写：

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要求的结果。

没有聚合的透视

Pivoting without aggregation

tsql

sql-server

pivot

aggregate-functions

编辑：这个答案在这里只是为了展示另一种完成这种旋转的方法。 @bluefeet 的回答是最好的解决方案！