Question

I have to implement SELECT ... FROM ... WHERE .. IN query in my stored procedure.

Below is the code from my stored procedure

ALTER PROCEDURE [dbo].[SP_GetQuestionSetMultiCat] 
    -- Add the parameters for the stored procedure here
    @PIN varchar(50),
    @CatIds varchar(50),
    @Range int,
    @Que_Type varchar(50)

AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    declare @qtId as int;
    select @qtId = Que_Type_Id from dbo.QuestionType_Tbl where Que_Type=@Que_Type;


    -- Insert statements for procedure here

        Select Top(@Range) 
            QId,
            Que_Type_Id,
            Que_Level_Id,
            Que_Category_Id, 
            Que,
            Opt1,
            Opt2,
            Opt3,
            Opt4,
            Ans 
        From 
            dbo.Que_Tbl 
        Where 
            (Que_Category_Id in (cast(@CatIds as varchar)))
            and (Que_Type_Id=@qtId) 
            and (Qid not in (Select Que_Id From dbo.UserQuestion_Mapping where PIN=@PIN and Que_typeID=@qtId))


END

---

Look at the where condition. The Que_Category_Id is int type. What i want to perform is –

Where Que_Category_Id in (1,2,3,4)

The in values i m passing is a string converted from my C# code.

When I am executing this query like –

exec SP_GetQuestionSetMultiCat '666777','4,5,6',5,'Practice'

it is generating an error –

Conversion failed when converting the varchar value ‘{4,5,6}’ to data type int.

Can anybody help me out how to solve this problem.

Thanks for sharing your valuable time.

Answer 1

1)Conversion failed when converting the varchar value '{4,5,6}' to data type int.

The reason of this error is data type precedence. INT data type has “higher” precedence than VARCHAR data type (16-INT vs. 27-VARCHAR).
So, SQL Server is trying to convert '{4,5,6}' to INT and not vice versa.

2) Instead, I would convert @CatIds to XML and then to a table variable (@IDs) using nodes(…) method:

SET ANSI_WARNINGS ON;

DECLARE @CatIds VARCHAR(50) = '4,5,6';

DECLARE @x XML;
SET     @x = '<node>' + REPLACE(@CatIds, ',', '</node> <node>') + '</node>';
DECLARE @IDs TABLE
(
    ID INT PRIMARY KEY
);
INSERT  @IDs(ID)
SELECT  t.c.value('.', 'INT')
FROM    @x.nodes('/node') t(c);

--Test    
SELECT  *
FROM    @IDs

3) The next step is to rewrite the query using IN (SELECT ID FROM @IDs) instead of in (cast(@CatIds as varchar)):

SET ANSI_WARNINGS ON;

ALTER PROCEDURE [dbo].[SP_GetQuestionSetMultiCat] 
    -- Add the parameters for the stored procedure here
    @PIN varchar(50),
    @CatIds varchar(50),
    @Range int,
    @Que_Type varchar(50)

AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    declare @qtId as int;
    select @qtId = Que_Type_Id from dbo.QuestionType_Tbl where Que_Type=@Que_Type;

    --Start: New T-SQL code
    DECLARE @x XML;
    SET     @x = '<node>' + REPLACE(@CatIds, ',', '</node> <node>') + '</node>';
    DECLARE @IDs TABLE
    (
        ID INT PRIMARY KEY
    );
    INSERT  @IDs(ID)
    SELECT  t.c.value('.', 'INT')
    FROM    @x.nodes('/node') t(c);
    --End

    -- Insert statements for procedure here

        Select Top(@Range) 
            QId,
            Que_Type_Id,
            Que_Level_Id,
            Que_Category_Id, 
            Que,
            Opt1,
            Opt2,
            Opt3,
            Opt4,
            Ans 
        From 
            dbo.Que_Tbl 
        Where 
            --The search condition is rewritten using IN(subquery)
            Que_Category_Id in (SELECT ID FROM @IDs)
            and (Que_Type_Id=@qtId) 
            and (Qid not in (Select Que_Id From dbo.UserQuestion_Mapping where PIN=@PIN and Que_typeID=@qtId))


END

4) Call stored procedure:

exec SP_GetQuestionSetMultiCat '666777','4,5,6',5,'Practice'