[Typo3] Condition on database fields

[Yomo]

Hi all,

I'm trying for days to find out how to accomplish the following:

* Check if a database field has a certain value.

I tried the TSRef and the TypoScript in Depth documents, but I can't 
seem to find anything on conditions for database fields. I expected 
something like [field:mycolumn = value], but only for the tt_content 
table such conditions are possible, not on your own table (in 
combination with the CONTENT object for sql-queries).

Hope it's clear what kind of condition I'm looking for. Any suggestion 
is welcome.

Thanks,
Yomo