Question

创建sql函数（Column typeX）

喜我有这张表：

  autoID   |    id   |    name   |    age    |   Tel
------------------------------------------
      1    |    1   |   Frank   |    40     |   null
      2    |    1   |   null    |    50     |   7834xx
      3    |    1   |   Alex    |    null   |   null
      4    |    1   |   null    |    20     |   null
      5    |    2   |   James   |    null   |   4100xx
      6    |    3   |   jan     |    24     |   null
      7    |    3   |   null    |    null   |   4100xx

我对select的查询：

SELECT TOP 10
(SELECT top(1) name FROM test1 where id=1 and name is not null order by autoID desc) as name ,(SELECT top(1) age FROM test1 where id=1 and age is not null order by autoID desc) as Age ,(SELECT top(1) Tel 
FROM test1 
where id=1 and Tel

不是autoID desc的空订单）作为Telephon FROM [dbo]。[test1] group by id

结果：

  autoID   |    id   |   name    |    age    |   Tel
------------------------------------------
      1    |    1    |   Alex    |    20     |  7834xx

我需要创建这样的函数：

CREATE FUNCTION TestSchema.MyfunctinX(@ColumnX @ColumnX.type)
RETURNS @ColumnX.type
AS
BEGIN
    DECLARE @value @ColumnX.type
    SELECT  top 1 @value from @ColumnX where @value is not null order by @autoID desc
    RETURN @value
END;
GO

对于我的选择查询，请使用Short：

Select Id, MyfunctinX(name) as [Name], MyfunctinX(age) as Age, MyfunctinX(Tel)
as Tel from yourtable Group by Id

有办法做到这一点吗？

Answer 1

您的结构效率不高。您可能更适合使用EAV结构（实体属性值）

示例

Select A.ID ,Name = [dbo].[MyFunction] (A.ID,'Name') ,Age = [dbo].[MyFunction] (A.ID,'Age') ,Tel = [dbo].[MyFunction] (A.ID,'Tel') From (Select Distinct ID From YourTable ) A

<强>返回

ID Name Age Tel 1 Alex 20 7834xx 2 James NULL 4100xx 3 jan 24 4100xx

UDF

CREATE FUNCTION [dbo].[MyFunction] (@ID int,@Field varchar(100)) Returns varchar(max) As Begin Return ( Select Top 1 with ties Value From (Select XMLData = cast((Select * from YourTable where ID=@ID For XML RAW) as xml)) A Cross Apply ( Select autoID = r.value('@autoID','int') ,Item = attr.value('local-name(.)','varchar(100)') ,Value = attr.value('.','varchar(max)') From A.XMLData.nodes('/row') as A(r) Cross Apply A.r.nodes('./@*') AS B(attr) Where attr.value('local-name(.)','varchar(100)') not in ('autoID') and attr.value('local-name(.)','varchar(100)')= @Field ) B Order By Row_Number() over (Partition By Item Order By autoID Desc) ) End

创建sql函数（列类型X）

1 个答案: