@Joost_ said:Borland InterBase - lacks every other thing you expect of SQL, ships with Delphi but has an annoying interfaceMySQL - when using InnoDB, mostly tolerable, but real DBA's sneer at it; no VIEWsPostgreSQL - sort of weird here and there, mostly O.K., but real DBA's sneer at it, for some reasonMicrosoft Access - not a real database, of course, or you wouldn't get it for free with Office(Prolog) - yes, you can use Prolog as a database through DDE. Much fun, not very useful.(XML/XPath) - for mostly non-relational data it's OK (as in: glorified .ini file); it's easier to ship an XML parser than a real DB; XPath is even more hateable than SQL(INI) - I once accidentally wanted to store a list of things in an .ini..... that was... painful.... and embarassing.
These are all the databases I actually have experience with...I wish people wouldn't use terms like "database" and "DBMS" interchangeably - it muddies the waters. None of the apps on the list are databases (the Windows registry might be, but not ini files). Some of the apps are DBMSes, some are file managers, some are... files?!DBMS people themselves have gradations of definition. For example, some people would call anything with support for latency and concurrency a DBMS, but to many, it has to be ACID compliant:http://en.wikipedia.org/wiki/ACIDBy the latter definition, Sybase and SQL Server do not qualify as DBMSes, but Oracle and PostgreSQL do qualify. That should give some clue as to Oracle's popularity.Actually, a lot of DBAs love PostgreSQL. It is easy to pick up, since its architecture is similar to Oracle's, and it has fewer technical drawbacks compared to the other cheap DBMSes. The real problem with it, in common with the other Open Source DBMSes, is that hardly anybody has paid experience administering it, which tends to scare off management. Sooner or later that problem will go away.