performance difference between UNION operator and OR in where clause Options

tables:

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

purpose: find all publication titles for books or journals.

precondition: both book and journal tables are not empty. (if either is empty, the following solution 2 will be wrong. See my old post "difference between UNION operator and OR in where clause Options" for details).

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

Both solutions are correct under the precondition.

My question is which one should use for better performance ?

My intuitive guess will be solution 2.

Any comments ?

Thanks ahead.

Thanks ahead. Received on Wed Jul 11 2007 - 08:21:45 CDT