如何在存储过程中编写带有动态表名称的Select查询？

Question

I am writing a stored-procedure. But the table name is dynamic in this procedure. I want to get row number from my variable table. But where will I set @rownumber with return of select query?

Create Proc update_eMail
    (@tablename nvarchar(50),
     @columnname nvarchar(50))
AS
Begin 

    Declare @q_getrowNumber NVARCHAR(MAX)
    Declare @rownumber int
    SELECT @rownumber =  Count(ID) FROM  quotename(@tablename) // doesnt work

END

Thanks in advance

Answer 1

Here is one way to achieve the goal using dynamic sql

declare @sql NVARCHAR(4000)= ''

set @sql = 'SELECT @rownumber = Count(ID) FROM '+ quotename(@tablename) 

exec sp_executesql @sql, N'@rownumber int output',@rownumber output

Answer 2

You write wrong Procedure for dynamic query Try This. It will Work.

ALTER PROC update_eMail(@tablename NVARCHAR(50))
AS
BEGIN 
DECLARE @RowNumber NVARCHAR(MAX)=''

  set @RowNumber='select Count(ID) FROM '+@tablename+''
  exec(@RowNumber)
END

OR Try below Code in your Query

ALTER PROC update_eMail1
(
   @tablename NVARCHAR(50)
)
AS
BEGIN
     DECLARE @sql NVARCHAR(4000)= '',@rownumber INT
     SET @sql = 'SELECT @rownumber = Count(ID) FROM '+quotename(@tablename) 

   EXEC sp_executesql @sql, N'@rownumber int output',@rownumber OUTPUT

   SELECT @rownumber

END

Answer 3

This one will be easiest for you:

Create Proc update_eMail
    @tablename nvarchar(50)
AS
Begin 
    EXEC ( 'SELECT Count(ID) FROM '+@tablename+'')
END