Joins and locks
Could some one please let me know how the joins and locks work in postgress and how is it different from oracle.
Rsponse much appreciated
One of the main differences is that Postgres, unlike Oracle, has in-depth documentation of an appropriate Goldilocks size. Go check it out -- seriously, everything you need to know is at http://www.postgresql.org/docs.
Table locking is a big topic, especially because lock granularity has changed a lot lately (its often on a specific row or column now, if the DBA knows what he's doing -- early advice, use the latest Postgres version) but the Postgres docs have you covered.
Nobody is going to sit here and re-write everything about table locking and then further explain all the ways that might interact with JOINs (though honestly, table locking generally doesn't affect reads/scans, so the impact is minimal in most cases, unless you write lots of race conditions into your code), and then go on an explain how Oracle works and then point out the differences.