difference between UNION operator and OR in where clause

tables:

1. publication(pubid, title)
2. book(pubid, date)
3. journal(pubid, date)

purpose: find all publication titles for books or journals.

solution 1: use set "union"

select title
from publication, ( (select pubid from book) UNION (select pubid from journal)) bj
where publication.pubid = bj.pubid

solution 2: use "or" operator in the where clause

select title
from publication, book, journal
where publication.pubid = book.pubid or publication.pubid = journal.pubid

This example is taken from some lecture notes about sql. The notes said the solution 2 was wrong.

Anyone knows why ?

Thanks ahead. Received on Tue Jul 10 2007 - 08:39:30 CDT