Question

我正在尝试根据链接到另一个表的列名的ID动态创建列。（我什至不知道是否有可能将其用于网页上的ssrs报告和gridview。）

看看下面的例子-“当前表”就是现在的样子。我为每个名字都有一栏。我已经创建了定义表。我想使当前表看起来像拟议的表，并使用选择表“创建”选择项中的列或使用定义表来使名称看起来像现在一样。

Answer 1

这是一种无需实际使用动态SQL即可“动态”取消数据透视的方法。

显然，戈登的性能更高，但是在这里，您不必声明这些列。

示例

Select  D.id
       ,[count] = C.Value
       ,A.ts
 From  CurrentTable A
 Cross Apply ( values (cast((Select A.* for XML RAW) as xml))) B(XMLData)
 Cross Apply (
                Select Item = a.value('local-name(.)','varchar(100)')
                      ,Value = a.value('.','int')    -- Use appropriate type
                 From  B.XMLData.nodes('/row')  as C1(n)
                 Cross Apply C1.n.nodes('./@*') as C2(a)
                 Where a.value('local-name(.)','varchar(100)') not in ('ts','OtherColToExclude')
             ) C
 Join   definition D on C.item=D.Name

返回

id  count   ts
1   5       2018-12-06
2   88      2018-11-01
2   18      2018-10-18
3   32      2018-10-27
4   6       2018-10-27

Answer 2

这是一个非常奇怪的数据结构。这是一种方法：

select d.id as definition,
       coalesce(c.p1, c.p2, c.p3, c.p4) as "count",
       c.ts
from current_table c join
     definition d
     on (d.name = 'p1' and p1 is not null) or
        (d.name = 'p2' and p2 is not null) or
        (d.name = 'p3' and p3 is not null) or
        (d.name = 'p4' and p4 is not null) ;

Answer 3

此外，您可以尝试使用unpivot来满足您的要求。有关更多详细信息，请参阅本文：https://docs.microsoft.com/en-us/sql/t-sql/queries/from-using-pivot-and-unpivot?view=sql-server-2017

----drop table [current_table] 
----drop table [definition] 
create table [current_table] 
(p1 int,
p2 int,
p3 int,
p4 int,
ts date )
insert into [current_table] values
(5,null,null,null,'20181206'),
(null,88,null,null,'20181101'),
(null,18,null,null,'20181018'),
(null,null,32,null,'20181027'),
(null,null,null,6,'20181014')

create table [definition] 
(id int,
name varchar(5) )
insert into [definition] values 
(1,'p1'),(2,'p2'),
(3,'p3'),(4,'p4')

;with cte as (
SELECT [name] ,[count],ts 
FROM [current_table]  t
UNPIVOT ([count] FOR [name] IN ([p1],[p2],[p3],[p4])) u)
select b.id,a.count,a.ts from  cte a  join [definition] b on a.name=b.name
/*
id          count       ts
----------- ----------- ----------
1           5           2018-12-06
2           88          2018-11-01
2           18          2018-10-18
3           32          2018-10-27
4           6           2018-10-14
*/


------dynamic-------------
DECLARE @ColNames varchar(1000);
SET @ColNames = '';
SELECT @ColNames =stuff((
    SELECT DISTINCT ',' + QUOTENAME(COLUMN_NAME)
    FROM INFORMATION_SCHEMA.COLUMNS p2
    WHERE TABLE_NAME = 'current_table'
      AND COLUMN_NAME like 'p%'
    FOR XML PATH(''), TYPE).value('.', 'varchar(max)')
            ,1,1,'')
DECLARE @CMD nvarchar(2000);
SET @CMD = ';with cte as (
SELECT [name] ,[count],ts 
FROM [current_table]  t
UNPIVOT ([count] FOR [name] IN ('+@ColNames+')) u)
select b.id,a.count,a.ts from  cte a  join [definition] b on a.name=b.name'
PRINT @CMD
execute sp_executesql @CMD
/*
;with cte as (
SELECT [name] ,[count],ts 
FROM [current_table]  t
UNPIVOT ([count] FOR [name] IN ([p1],[p2],[p3],[p4])) u)
select b.id,a.count,a.ts from  cte a  join [definition] b on a.name=b.name
id          count       ts
----------- ----------- ----------
1           5           2018-12-06
2           88          2018-11-01
2           18          2018-10-18
3           32          2018-10-27
4           6           2018-10-14
*/

希望它可以为您提供帮助。

最好的问候，

瑞秋

SQL Server：从链接到另一个表的ID列动态创建列

3 个答案: