[英]Pass Column Name as parameter
我想将PassColumn名称用作我的SP中的参数,并且如果我的tat列存在于第一个表(Batch_Master)中,则想对该列中的值进行赋值,
如果在我的第二个表(GTIN_Master)存在列,希望从达表列取值,每个表都列如.. Batch_Master(Batch_M_id,GTIN(主键),....等GTIN_Master(GTIN(外键),..等等)
我有Batch_M_id和列名作为参数。
注意:列名称具有随机数据类型,某个时间int或某个时间datetime等
我尝试关注SP
CREATE PROCEDURE dbo.StoredProcedure2
@columnName varchar(50),
@batchmId int
AS
if exists(select * from sys.columns
where Name = N'columnName' and Object_ID = Object_ID(NBatch_Master'))
begin
select @columnName from Batch_Master
end
else
begin
select @columnName
from GTIN_Master inner join Batch_Master
on GTIN_Master.GTIN = Batch_Master.GTIN
where Batch_M_id =@batchmId
end
RETURN
当您不完全知道要执行的查询结构时需要什么,那么您必须创建一个动态查询,这实际上是模板查询的一种形式。
CREATE PROCEDURE dbo.StoredProcedure2
@columnName varchar(50),
@batchmId int
AS
DECLARE @SQL1 AS VARCHAR(MAX)
DECLARE @SQL2 AS VARCHAR(MAX)
SET @SQL1 = 'select ' + @columnName + ' from Batch_Master'
SET @SQL1 = 'select ' + @columnName + '
from GTIN_Master inner join Batch_Master
on GTIN_Master.GTIN = Batch_Master.GTIN
where Batch_M_id =' + CONVERT(VARCHAR,@batchmId)
IF EXISTS(SELECT * FROM sys.columns WHERE Name = @columnName and Object_ID = Object_ID(N'Batch_Master'))
BEGIN
EXEC (@SQL1)
END
ELSE
BEGIN
EXEC (@SQL2)
END
上面的代码可以做您想要的,但是容易出错。 例如,如果第二个查询中使用的表中不存在传入参数的列,该怎么办? 您可能还需要在第二种情况下检查是否存在。
DECLARE @SQL VARCHAR(MAX)
SET @SQL = 'select ' + @columnName + ' from Batch_Master'
EXECUTE(@SQL)
此SQL:
set nocount on
go
create table One (id int, name varchar(25))
go
create table Two (id int, value varchar(25))
go
insert into One values (1, 'Table One')
insert into Two values (1, 'Table Two')
go
create procedure sp_test_colname
@colname sysname
as
declare @sql nvarchar(2048)
if exists (select 1 from sys.columns where name = @colname and object_id = object_id(N'One'))
set @sql = 'select [' + @colname + '] from [One]'
else
if exists (select 1 from sys.columns where name = @colname and object_id = object_id(N'Two'))
set @sql = 'select [' + @colname + '] from [Two]'
if @sql <> ''
exec sp_executesql @sql
go
exec sp_test_colname 'name'
exec sp_test_colname 'value'
exec sp_test_colname 'somethingelse'
go
drop procedure sp_test_colname
drop table One, Two
返回以下内容:
name
-------------------------
Table One
value
-------------------------
Table Two
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