Solution

Create one view for each group of users, and deny them access to the underlying table(s) ref-view ref-deny.

Discussion

You can create alternative views of your database with CREATE VIEW <viewname> AS SELECT.... To a user this appears to be a table, but you can control what underlying data shows through. The SELECT query can be anything you like - it can involve JOINs, UNIONs or GROUP BY if you want. So, if the accounts department only needs to see completed orders:

CREATE VIEW accts_orders AS SELECT * FROM orders WHERE ord_delivered IS NOT NULL;
   

You then need to make sure that accounts has access to this view and not to the underlying table:

GRANT ALL ON accts_orders TO accounts;
REVOKE ALL ON orders FROM accounts;
   

You will need to be a superuser (postgres) or the owner of the database objects to do this. Possible permissions are: SELECT, INSERT, UPDATE, DELETE, RULE, ALL.