query help

[NSmoller]

What is the difference between these?

SELECT LocalList.MD, Locallist.patient, locallist.SSN, locallist.drug, locallist.Lastfill
FROM Locallist, Duplicates
WHERE Locallist.Patient=Duplicates.Patient
ORDER BY locallist.MD, locallist.LastFill;

SELECT LocalList.MD, Locallist.patient, locallist.SSN, locallist.drug, locallist.Lastfill
FROM Locallist
WHERE Locallist.Patient IN (Select patient from duplicates)
ORDER BY locallist.MD, locallist.LastFill;

 

[lespaul]

the first creates a cartesan product of the two tables. check out this link to understand exactly what that means.

The second uses a subquery (a query within another query).

Is there something specific that you wanted to know about them?

Leslie

Anything worth doing is a lot more difficult than it's worth - Unknown Induhvidual

Essential reading for anyone working with databases: The Fundamentals of Relational Database Design