Re: How does this query work.....?

pg_class holds the relation information (tables, etc)
pg_attribute holds attribute information (attname), it
keeps the oid of the relation it's on in attrelid and the
oid of the type as atttypid
pg_type holds type information (typname)

The attnum>0 is to limit the check to user attributes.
There are additional attributes (oid, xmin, etc...)
defined on the tables that have attnum<0 and you usually
don't care about that.

On Fri, 9 Mar 2001 RbrtBrn3(at)aol(dot)com wrote:

> Hi,
>
> I am using the following query to find the attributes of a given table, and
> their datatypes:
>
> select typname,attname
> from pg_class c, pg_attribute a,pg_type t
> where relname = 'table_name' and
> attrelid = c.oid and
> atttypid = t.oid and
> attnum > 0;
>
> Can anybody explain how this query actually works - I cannot figure it.
> Thanks in advance.
>
> Rob Burne.
>