Question

I need to somehow use the CASE syntax (which is beyond me) to affect the database results based on criteria.
I have a bunch of royalties in 0.# form (royalty)
I have a title ID # (title_id) and I need to show the new increase in royalties so that I can use the data.

IF: they have a current royalty of 0.0 - 0.1 = 10% raise
IF: they have 0.11 - 0.15 = 20% raise
IF: royalty >= 0.16 =  20% raise

Any help would be much appreciated.

    create table royalites (
title_id    char(6),
lorange     integer,
hirange     integer,
royalty     decimal(5,2));

Answer 1

Actually, you don’t need to use the case statement:

update royalties set royalty = royalty * 1.2
    where royalty >= 0.16;
update royalties set royalty = royalty * 1.2
    where royalty >= 0.11 and royalty < 0.16;
update royalties set royalty = royalty * 1.1
    where royalty < 0.11;

(under transactional control if you need atomicity). You could possibly combine the first two if they have the same multiplier as your question states.

It works by ensuring you do the higher values first and limit what rows get affected in the where clause.

If you feel you must use a case statement:

update royalties set royalty =
    case when royalty >= 0.16 then royalty * 1.2
    case when royalty >= 0.11 and royalty < 0.16 then royalty * 1.2
    case when royalty <  0.11 then royalty * 1.1
    end;

To just change what you’re pulling out of the table (rather than changing the table itself) and compare it with the current:

select title_id, lorange, hirange, royalty,
    case when royalty >= 0.16 then royalty * 1.2
    case when royalty >= 0.11 and royalty < 0.16 then royalty * 1.2
    case when royalty <  0.11 then royalty * 1.1
    end as new_royalty
    from royalties;