How do system tables relate to other tables in postgresql - Mailing list pgsql-general

Hi,

Hope you can help me out.

I'm trying to write a select statement which returns the all the columns of
a table with a 'not null' modifier.

I realise that I will need to use the system tables but can't work out which
columns of which system tables to include in my statement.

Thanks for any help in advance,
Graeme