I wonder if it's a problem, if a table or column name contains upper case letters. Something lets me believe databases have less trouble when everything is kept lower case. Is that true? Which databases don't like any upper case symbol in table and column names?
I need to know, because my framework auto-generates the relational model from an ER-model.
(this question is not about whether it's good or bad style, but only about if it's a technical problem for any database)
As far as I know there is no problem using either uppercase and lowercase. One reason for the using lower case convention is so that queries are more readable with lowercase table and column names and upper case sql keywords:
SELECT column_a, column_b FROM table_name WHERE column_a = 'test'
It is not a technical problem for the database to have uppercase letters in your table or column names, for any DB engine that I'm aware of. Keep in mind many DB implementations use case sensitive names, so always refer to tables and columns using the same case with which they were created (I am speaking very generally since you didn't specify a particular implementation).
For MySQL, here is some interesting information about how it handles identifier case. There are some options you can set to determine how they are stored internally. http://dev.mysql.com/doc/refman/5.0/en/identifier-case-sensitivity.html
The SQL-92 standard specifies that identifiers and keywords are case-insensitive (per A Guide to the SQL Standard 4th edition, Date / Darwen)
That's not to say that a particular DBMS isn't either (1) broken, or (2) configurable (and broken)
From a programming style perspective, I suggest using different cases for keywords and identifiers. Personally, I like uppercase identifiers and lowercase keywords, because it highlights the data that you're manipulating.
As far as I know for a common L.A.M.P. setup it won't really matter - but be aware that MySQL hosted on Linux is case sensitive!
To keep my code tidy I usually stick to lower case names for tables and colums, uppercase MySQL-Code and mixed Upper-Lower-Case variables - like this:
SELECT * FROM my_table WHERE id = '$myNewID'
The column names which are mixed case or uppercase have to be double quoted in PostgreSQL. If you don't want to worry about it in the future, name it in the lower case.
MySQL - the columns are absolutely case insensitive. And it can lead to problems. Say someone has written "mynAme" instead of "myName". The system would work fine, but once some developer would go searching for it through the source code, they might overlook it, and you all get in trouble.
Think this is worth emphasizing: If a binary or case-sensitive collation is in effect, then (at least in Sql Server and other databases with rich collation features) identifiers and variable names WILL be case sensitive. You can even create tables whose names differ only in case. (—I am not sure the info above about the sql-92 standard is correct—if so, this part of the standard is not widely followed.)