what is the best way to get key information in postgres?

Hi,

I want to know what is the best way to get all the keys(unique, primary,
foreign, multiple) for a table in postgres, I actually found this query
and i am not sure if it is the best way to get the keys info:

select r.relname as "Table", c.conname as "Constraint Name", contype as
"Constraint Type", conkey as "Key Columns", confkey as "Foreign
Columns", consrc as "Source" from pg_class r, pg_constraint c where
r.oid=c.conrelid and relname='tablename';

And if the above query is good, how can I display in the output the
column names that relates to the key.

Can I use that query to get The multiple key info? or what is the best
way to do so?

I will really appreciate your help.

Thanks,

Noura Elhawary