vc的ado中调用存储过程，带有字符串类型的输出参数

[xbottle001]

语句是这样：

select a from a_table where ad_id = 0010101

这时候a是唯一的字符串。
那么我要怎么在存储过程中写，才能让这个字符串输出呢？
以及在vc的ado中要怎样写呢？

[-狙击手-]

create proc pr_test
@s varchar(100) output
as
begin
select @s = a from a_table where ad_id = '0010101'
end
go


ado你就gg 吧，一大把一大把的

[xbottle001]

是这样的：

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

ALTER PROCEDURE [dbo].[aaaaproc]
@IndexValue int, 
@Combostring nvarchar (256) output, 
@NLen INT 
AS
BEGIN
declare @sql nvarchar(4000)

SET @sql ='SELECT @Combostring = row_value
					  FROM combobox_temp_table
					  WHERE index_value = '+ltrim(@IndexValue )
exec sp_executesql @sql ,N'@Combostring  int output',@Combostring  output
select @sql as '@sql'
select @Combostring as '@Combostring'
END
--sql server执行如下
USE [aaaaaaaa]
GO
DECLARE @IndexValue int, 
@Combostring varchar (256) , 
@NLen INT 

EXEC	 [dbo].[aaaaproc]
@IndexValue = 1,@Combostring = @Combostring output,@NLen = 0

SELECT	@Combostring as '@Combostring'
GO

但是在执行的时候，会提示我所取得的字符串：
消息 245，级别 16，状态 1，第 1 行
在将 nvarchar 值 '我所取得的字符串 ' 转换成数据类型 int 时失败。

[xbottle001]

找到了

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

ALTER PROCEDURE [dbo].[aaaaproc]
@IndexValue int, 
@Combostring nvarchar (256) output, 
@NLen INT 
AS
BEGIN
declare @sql nvarchar(4000)

SET @sql ='SELECT @Combostring = row_value
                      FROM combobox_temp_table
                      WHERE index_value = '+ltrim(@IndexValue )
exec sp_executesql @sql ,N'@Combostring  int output',@Combostring  output
--这里写错了，@Combostring  不用该是int类型
select @sql as '@sql'
select @Combostring as '@Combostring'
END
--sql server执行如下
USE [aaaaaaaa]
GO
DECLARE @IndexValue int, 
@Combostring varchar (256) , 
@NLen INT 

EXEC     [dbo].[aaaaproc]
@IndexValue = 1,@Combostring = @Combostring output,@NLen = 0

SELECT    @Combostring as '@Combostring'
GO