如果有输出参数则必须使用output做修饰符

alter proc ABC
(
  @OutValue  nvarchar(20)  output
)
as
set @OutValue='aabbcc'
select a,b from ab
print @OutValue 

alter proc ABCV
as
Declare @OutValuea nvarchar(20)

Exec ABC @OutValue=@OutValuea output
select @OutValuea
return 2