Question

I am trying to do something like this in a CASE WHEN in my query but it is not taking the AND part, it says its an error in the syntax, it would not take && either. I would appreciate any help as I am not to much of a SQL guru..

   Total =
               CASE Payment.ID
                    WHEN 1 THEN  mytable.Total
                    WHEN 4 AND trans.Amount IS NULL THEN mytable.Total
                    WHEN 4 AND trans.Amount IS NOT NULL THEN mytable.Total - trans.Amount
                    ELSE '0'
               END,

Answer 1

Here is one way to do it. Change the expression to something like this.

Script:

Total = (CASE 
            WHEN Payment.ID = 1
                THEN  mytable.Total
            WHEN Payment.ID = 4 
                AND trans.Amount IS NULL 
                    THEN mytable.Total
            WHEN Payment.ID = 4 
                AND trans.Amount IS NOT NULL 
                    THEN mytable.Total - trans.Amount
            ELSE '0'
        END),

There are two types of CASE expression namely Simple and Searched. You cannot combine Simple and Searched in the same expression.

Simple:

CASE input
    WHEN 1 THEN 'a'
    WHEN 2 THEN 'b'
    WHEN 3 THEN 'c'
    ELSE ''
END

Searched – Example 1: In the simplest form.

CASE 
    WHEN input = 1 THEN 'a'
    WHEN input = 2 THEN 'b'
    WHEN input = 3 THEN 'c'
    ELSE ''
END

Searched – Example 2: Involving multiple columns. You can add multiple columns in each of the WHEN statements.

CASE 
    WHEN input = 1 AND second_column = 2 THEN 'a'
    WHEN input = 2 AND third_column  = 3 THEN 'b'
    WHEN input = 3 AND (second_column = 4 OR third_column = 6) THEN 'c'
    ELSE ''
END