Question: We all have our favourite database. If you look objectively at your chosen database, what drawbacks does it have and what could be improved?

The rules:

* One reply per drawback with;
* a short description of the limitation, followed by;
* a more detailed description, an explanation of how it could be done better or an example of another technology that does not have the same limitation.
* Do not diss any database that you haven't used extensively. It is easy to take potshots at other technologies but we want to learn form your experience, not your prejudice.

Answer: 
Oracle databases are quite expensive

Oracle does what it does well but the licensing costs are horrendous. That has been improved by the release of Oracle XE but the limitations of that mean that it is a growth constraint on you solution.
Any SQL DBMS

Defect: Duplicate rows

One of the virtues of the relational model is that it represents everything without duplicate tuples, i.e. using relations, which have keys and no duplicates. Unfortunately SQL isn't built that way. This makes the database developer's life needlessly difficult. SQL developers have to deal with tables without keys and debug queries that return duplicate rows.