Question

Let say I have this table,

A    B
-------
1    A
2    C
3    A
4    NULL
5    B
6    A

I have only a single parameter in stored procedure. I need to pass a single parameter @param. I need to select all rows equal to A or select all rows not equal to A. I have only a single parameter @param. If @param = ‘A’ select all rows with A and If @param <> ‘A’ select all rows with not equal to A.

Edit:

Here is 1 approach I have found. Not sure which approach is best one.

DECLARE @Param VARCHAR(5)='NOt A'

DECLARE @tbl TABLE(A INT,B VARCHAR(5))

INSERT INTO @tbl(A,B)
VALUES
    (1,'A'),
    (2,'C'),
    (3,'A'),
    (4,NULL),
    (5,'B'),
    (6,'A')

SELECT  * 
FROM    @tbl 
WHERE 1 = 
        (
            CASE    WHEN @param = 'A' 
                    THEN 
                    (
                        CASE WHEN B = 'A' THEN 1 ELSE 2 END
                    ) 
                    ELSE 
                    (
                        CASE WHEN (B IS NULL OR B <> 'A') THEN 1 ELSE 2 END
                    ) 
                    END
        ) 

Answer 1

So if I understand you correctly, you basically want to select all rows equal to A if the value of @param is indeed A – and all other rows if it’s not A ??

Something like:

 CREATE PROCEDURE dbo.SelectRows @Param CHAR(1)
 AS 
 BEGIN
   IF @Param = 'A' THEN

     SELECT A, B
     FROM dbo.YourTable
     WHERE B = 'A'

   ELSE

     SELECT A, B
     FROM dbo.YourTable
     WHERE B <> 'A' OR B IS NULL

 END