Comparison of different SQL implementations
By fellow Dane, Troels Arvin:
The following tables compare how different DBMS products handle various SQL (and related) features. If possible, the tables also state how the implementations should do things, according to the SQL standard.
This is very thorough and interesting. It does a really good job of explaining why creating applications that run on multiple database platforms is a hard thing.
It's encouraging to see that my favourite RDBMS, PostgreSQL seems to lead the pack (although it has a few transgressions of its own.
There's little good to say about MySQL in this comparison. Several flagrant violations of the standard and slow to adopt new SQL features.