Relational operators

Hi,

I was wondering if the following issue is in fact a bug, or just
inconvenient behaviour...

say a table looks like this:

table
---
c (varchar)
'20'
'0'
'-10'
'klj'
'> 5'
'qwerty'
'< 6'

The query select * from table where c < 5 will return for instance the
tuple containing '20'.
In other words, postgresql 8.0 will not automatically cast the results
to a numeric value and only take into account those tuples that can be
cast (not 'klj' nor 'qwerty') ... unlike some other databases ....

Any (standard) solutions to this problem?

-greetz, pj