How to ignore a parameter in stored procedure if its value is null

Question

I have a stored procedure in which I have to join 10 tables and use WHERE condition to filter the records based on the parameters passed in the stored procedure

Answer 1

Let's play with Dynamic - SQL:

CREATE PROCEDURE [dbo].[my_procedure]
     @var1 VARCHAR(100) = NULL,
     @var2 VARCHAR(100) = NULL,
     @var3 VARCHAR(100) = NULL,
     @var4 VARCHAR(100) = NULL,
     /* ........  */ 
     @var10 VARCHAR(100) = NULL,
     @debug INT         = 0
AS
BEGIN
SET NOCOUNT ON;

DECLARE 
    @sql        NVARCHAR(MAX),                                
    @paramlist  NVARCHAR(4000),                              
    @nl         CHAR(2) = CHAR(13) + CHAR(10);


/* Main query here */
SELECT @sql = 
   'SELECT * 
    FROM tab1 AS a
    INNER JOIN tab2 AS b
      ON a.rollnumber = b.rollnumber
    INNER JOIN tab3 AS c
      ON c.city = b.city
    /* ........ and so on */
    INNER JOIN tab10 AS j
      ON J.id = i.id
    WHERE 1 = 1 ' + @nl;

IF @var1 IS NOT NULL                                            
    SELECT @sql += ' AND a.id = @var1' + @nl;  

IF @var2 IS NOT NULL                                            
    SELECT @sql += ' AND b.id = @var2' + @nl;  

/* ... */

IF @var10 IS NOT NULL                                            
    SELECT @sql += ' AND j.id = @var10' + @nl;

/* If sorting needed just add it;
SELECT @sql += ORDER BY a.id;
*/

IF @debug = 1
    PRINT @sql;


SELECT @paramlist = 
      '@var1     VARCHAR(100),   
       @var2     VARCHAR(100),
       /* ... */
       @var10     VARCHAR(100)';

/*CREATE TABLE #temp definition here */

INSERT INTO #temp(col1, col2, ...)
EXEC [dbo].[sp_executesql]
           @sql,
           @paramlist,
           @var1,
           @var2,
           /* ... */
           @var10;

IF @@ROWCOUNT < 10 
THEN
    SELECT *       /* Use column names */
    FROM #temp;
ELSE
    PRINT 'Cannot display the records as count is more than 10';
END

Usage as any normal stored procedure + debug if want to see query:

 EXEC [dbo].[my_procedure]
            @var1 = 'AAA'
           ,@var2 = 'BBB'
           ,@debug = 1;

• Formatting is everything, especially when Dynamic-SQL is used.
• Instead of SELECT COUNT(*) FROM #temp use @@ROWCOUNT;
• Printing from SP is not good practice, better to return some value to indicate it in OUT parameter.
• If you don't like WHERE 1 = 1 you can first check if all arguments are NULLs and skip it.
• You don't need to use Dynamic SQL at all, just use IF THEN ELSE IF THEN ELSE IF ... ELSE and do massive duplication of hard to maintain code (if Line Of Code is metric used to measure your productivity it can be useful)