Cross-platform, standards compliant, open source, and completely awesome, PostgreSQL (pronounced postgres queue el) is the obvious choice for any data-loving nerd. PostgreSQL has always held the position of the most advanced open source database. (Seriously, though — we know what you're thinking — don't even mention MySQL.)
Lintel enjoys PostreSQL's large collection of versatile features. For the serious dataphile, PostgreSQL creates the cliche "kid in the candy store" moment; even serious users occasionally find lesser known, yet uber-powerful, features and capabilities.
You need a powerful SQL server, such as PostgreSQL, with its many features like updatable views, materialized views, triggers, replication, GiST, table partitioning, foreign data wrappers, and the list goes on ... and on.
Before you go all NonSQL on us, you need to give PostreSQL serious consideration. Sure, that movement has its place (and we're huge fans of some NonSQL offerings), but we find most people abandon relational databases prematurely because they don't understand how to leverage the underlying database servers. If you give PostreSQL a chance, it will rock your world.