Stored Procedure not execute as expected

Question

I have written following stored procedure

CREATE procedure [dbo].[findUSerID]
    @Column_name varchar(50),
    @TR_ID int
AS
    DECLARE @sql nvarchar(max) = 'SELECT ' +@Column_name+ ' 
                                  FROM Transfer_TB 
                                  WHERE TID =' + CAST(@TR_ID AS VARCHAR(10))

    EXEC sp_executesql @sql

Table definition :

CREATE TABLE [dbo].[Transfer_TB]
(
    [TID] [int] NULL,
    [ABC] [varchar](20) NULL,
    [XYZ] [varchar](50) NULL,
    [LMN] [varchar](50) NULL,
    [PQR] [varchar](50) NULL,
)

But it does not return the proper output.

Like I have called it from my asp page code for that using n tier architecture.

public string check_validID(string branch,int trId)
{
    string user_Br_ID;
    clsBranch_TB objbr = new clsBranch_TB();
    clsUserTB objuser = new clsUserTB();
    objuser.User_Branch = 'XYZ';
    objuser.Extra_Int = 32;

    DataSet ds = clsAdminLogic.findUSerID(objuser);

    if (ds.Tables[0].Rows.Count == 0)
    {
        user_Br_ID = clsAdminLogic.getno_of_Emp(objbr);
    }
    else 
    {
        user_Br_ID = ds.Tables[0].Rows[0][0].ToString();
    }

    return user_Br_ID;
}

 public static DataSet findUSerID(clsUserTB objuser)
 {
        DataSet ds = DataAccessLayer.clsLogs.findUSerID(objuser);
        return ds;
 }

 public static DataSet findUSerID(clsUserTB objuser)
 {
     SqlParameter[] param = {
                              new SqlParameter("@TR_ID",objuser.Extra_Int),
                              new SqlParameter("@Column_name",objuser.User_Branch)
                            };
     DataSet ds = DataAccessLayer.SqlHelper.FillDataNewRJ(
                     DataAccessLayer.clsDataAccessLayer.con.ConnectionString.ToString(),
                     CommandType.StoredProcedure, "findUSerID", (param)
            );
     return ds;
}

As it executes it, there is value present in database, but still it enters into if part of that function.

Please help me and guide if something wrong in above code

Answer 1

i found solution for this problem, actually that particular record contains values instead of selective column that's why query returning the null value. So i just have added one condition my stored procedure to fix it .

ALTER procedure [dbo].[findUSerID]
@Column_name varchar(50),
@TR_ID int

AS

DECLARE @sql nvarchar(max) = 'SELECT ' +@Column_name+ ' 
FROM Transfer_TB where TID =' + CAST(@TR_ID AS VARCHAR(10))+' 
and '+@Column_name+'<> null'

exec sp_executesql @sql

Answer 2

there is value present in database, but still it enters into else part of that function

I assume this is the part you're talking about (there are 3 functions in that code)

if (ds.Tables[0].Rows.Count == 0)
{
    user_Br_ID = clsAdminLogic.getno_of_Emp(objbr);
}
else 
{
    user_Br_ID = ds.Tables[0].Rows[0][0].ToString();
}

Yes. Your if goes into the else if the rows are not 0. It's doing exactly what its being told. That basic logic error is the least of your worries though. You're storing branches as columns?

Answer 3

Your stored procedure is prone to Sql-Injection. do the following to protect yourself against it.

CREATE procedure [dbo].[findUSerID]
   @Column_name SYSNAME
  ,@TR_ID       INT
AS
BEGIN
  SET NOCOUNT ON;
  DECLARE @sql nvarchar(max);

  SET @sql = N' SELECT ' + QUOTENAME(@Column_name) 
           + N' FROM Transfer_TB '
           + N' WHERE TID = @TR_ID '

  exec sp_executesql @sql
                    ,N'@TR_ID int'
                    ,@TR_ID 

END

If your Stored procedure is returning a scalar value "UserID" as the name suggest you should be doing something like......

CREATE procedure [dbo].[findUSerID]
   @Column_name SYSNAME
  ,@TR_ID       INT
  ,@UserID      INT OUTPUT
AS
BEGIN
  SET NOCOUNT ON;
  DECLARE @sql nvarchar(max);

  SET @sql = N' SELECT @UserID =  ' + QUOTENAME(@Column_name) 
           + N' FROM Transfer_TB '
           + N' WHERE TID = @TR_ID '

exec sp_executesql @sql
                  ,N'@TR_ID int , @UserID INT OUTPUT'
                  ,@TR_ID 
                  ,@UserID OUTPUT

END