Question

I am expecting this to return the value of ‘C’, but it is returning ‘A’. I cannot seem to figure out why this will not work as my logic looks sound.

DECLARE @WeekStartDay varchar(10)
DECLARE @WeekEndDay varchar(10)
SET @WeekStartDay = 'Saturday'
SET @WeekEndDay = 'Saturday'



SELECT

    CASE

        WHEN (
                ((@WeekStartDay = 'Saturday') OR (@WeekStartDay = 'Sunday'))
                         AND 
                ((@WeekEndDay <> 'Saturday') OR (@WeekEndDay <> 'Sunday'))
            )
            THEN 'A'

        WHEN (
                ((@WeekEndDay = 'Saturday') OR (@WeekEndDay = 'Sunday'))
                        AND 
                ((@WeekStartDay <> 'Saturday') OR (@WeekStartDay <> 'Sunday'))
            )
            THEN 'B'
        WHEN (
                ((@WeekEndDay = 'Saturday') OR (@WeekEndDay = 'Sunday'))
                        AND 
                ((@WeekStartDay = 'Saturday') OR (@WeekStartDay = 'Sunday'))
            ) 
            THEN 'C'

    END AS Result

My intended function is:

I am trying to get it to deteremine

IF the @WeekStartDay = Saturday or Sunday AND @WeekEndDay IS NOT Saturday or Sunday THEN ‘A’

IF the @WeekEndDay = Saturday or Sunday AND @WeekStartDay IS NOT Saturday or Sunday THEN ‘B’

IF @WeekStartDay AND @WeekEndDay BOTH = Saturday or Sunday THEN ‘C’

Hmmm from responses looks like my logic was way more off than I thought.

Answer 1

Substituting the parameter values in as literals gives (for the first case)

         WHEN ((('Saturday' = 'Saturday')  OR ('Saturday' = 'Sunday'))
                           AND 
               (( 'Saturday' <> 'Saturday') OR ( 'Saturday' <> 'Sunday')))

Which is

         WHEN ((True OR False) AND (False OR True))

Which is

         WHEN (True AND True)

Which is

         WHEN (True)

I think you need

SELECT
    CASE WHEN @WeekStartDay IN ('Saturday', 'Sunday') THEN 
        CASE WHEN @WeekEndDay IN ('Saturday', 'Sunday') THEN 
            'C'
        ELSE 
            'A'
        END 
    ELSE 
        CASE WHEN @WeekEndDay IN ('Saturday', 'Sunday') THEN 
            'B'
        ELSE 
            NULL /*You haven't said what should happen here?*/
        END 
    END
 AS Result