using not with sub-queries

Question

I have been asked to display results in my sql server database for the following question

What software packages are not installed on any HP computers?

Answer 1

You can use NOT EXISTS with a correlated subquery that joins the other tables together, and contains your filter condition:

select
pk.pack,
pk.packname,
pk.packv,
pk.packtype,
pk.packcost
from package pk
where not exists (
                    select 1
                    from software s
                    inner join pc on pc.tagnum = s.tagnum
                    inner join computer c on c.comp = pc.comp
                    where s.pack = pk.pack
                    and c.mfrname = 'HP'
                 )
order by pk.pack;

Result

| pack |         packname | packv |        packtype | packcost |
|------|------------------|-------|-----------------|----------|
| AC11 | Quick Accounting |   4.1 |      Accounting |   754.95 |
| AC12 |   Accounting MIS |   4.0 |      Accounting |     2000 |
| AC13 |        Quickbook |  2005 |      Accounting |      300 |
| DB11 |            Manta |   1.5 |        Database |      380 |
| DB13 |       SQL Server |  2005 |        Database |      500 |
| DB14 |           My SQL |  2005 |        Database |      300 |
| SS11 |          Easycal |   5.5 |     Spreadsheet |   225.15 |
| WP04 |       Word Power |     2 | Word Processing |      118 |
| WP07 |        Good Word |   3.2 | Word Processing |       35 |
| WP14 |           GOOGLE |     2 | Word Processing |      118 |

SQL Fiddle example