How to you pick a database.

How to you pick a database. Normal answer is the customer desides for you if is a large project with a must run on X.

If given a free choice the decision goes like this.

1. Database size > x 100 server memory given me Oracle any day.
2. Database size < x 10 server memory any big name database will work well
   
3. Database <= server memory would use postgres as default , using it on off for years, its does everything a rdms should.

When your having rows appears in 10M blocks oracle partitioning and other trick are a god send. Otherwize most of the database out they do eventhing needed.

In the old 2 tier client/server days, always went for oracle because of Pl/Sql and used the oralce as combined application server and database with all business logical in the database. Now with n-tier only really want the database to do SQL database stuff to dont care so much. In porting applications arround the playing field very level for both open source and commerical offerings. All major ones to joins,foreign keys, unions etc.