When to use MySQL vs PgSQL?
silentbicycle: While this is somewhat more subjective, documentation and tutorials I've read for PostgreSQL consistently seem better informed about relational databases than MySQL's. I keep seeing cases where somebody is having performance issues with MySQL, and it turns out they neglected to do something basic like indexing their tables. This is probably partially due to its reputation of being good for the web, and thus getting a used by a lot of people who kinda-sorta know PHP but know nothing about the relational paradigm, but MySQL also has a history of ignoring fundamental relational concepts 
(http://www.reddit.com/r/programming/comments/764fp/mysql_vs_...), so it's not a coincidence.Also, it irritates me when people write off relational databases because of a bad experience naively using MySQL, but that's neither here nor there.You should probably program for a neutral wrapper and do actual testing to determine which will work better for you, though. I like PostgreSQL, and have had very good results with it, but I've never come close to needing the sort of dramatic scalability that people seem to worry so much about.