Oracle is closed source, if something goes wrong you cannot look at
the source and fix it yourself or submit a detailed bug request. Not
everyone does this but it is an important point for some people. It
also costs a lot of money. Starting with the low end processor license
Standard Edition One = $5,800
up to the top end
Enterprise Edition = $47,500
There are probably other charges and taxes to pay and you will need a
skilled database guy to make the most of it. Whats the point paying
thousands of dollars for a product and then not using it to its full
potential. Unless you have money to throw away
As to MySQL, at the moment it looks like Oracle is starting to close
that up too, or at least make it less open source friendly. You might
want to give it a wide berth until the dust settles on this one. There
are drop in replacements for MySQL such as MariaDB. Utilise MySQL
skills and tools without lock in from Oracle.
Postgres is good, we use it exclusively.
Sqlite is good for small things but when it gets large I believe (but
have no first hand experience) starts to show its limitations. Perhaps
others with better experience could comment here. The advantage of
MySQL and PostgreSQL is that tools exist to replicate and shard the
database should things get too large for a single database server,
these tools do not exist for Sqlite.
MondoDB is a document based solution and not a relational database so
its use would depend on if your data is better suited to the
relational model or the document model. We found that inserts into
MongoDB were significantly slower than PostgreSQL and so was not
suitable for our needs, pity really because it would have been a
better fit for the data. But we update the data far more often then we
If your data is really a document model then you might also look at
eXist, an XML database.