When you create a database object, you become its owner. By default, only the owner of an object can do anything with the object. In order to allow other users to use it, privileges must be granted. (However, users that have the superuser attribute can always access any object.)
There are several different privileges: SELECT, INSERT, UPDATE, DELETE, RULE, REFERENCES, TRIGGER, CREATE, TEMPORARY, EXECUTE, and USAGE. The privileges applicable to a particular object vary depending on the object's type (table, function, etc). For complete information on the different types of privileges supported by PostgreSQL, refer to the GRANT reference page. The following sections and chapters will also show you how those privileges are used.
The right to modify or destroy an object is always the privilege of the owner only.
Note: To change the owner of a table, index, sequence, or view, use the ALTER TABLE command. There are corresponding ALTER commands for other object types.
To assign privileges, the GRANT command is used. For example, if joe is an existing user, and accounts is an existing table, the privilege to update the table can be granted with
GRANT UPDATE ON accounts TO joe;
To grant a privilege to a group, use this syntax:
GRANT SELECT ON accounts TO GROUP staff;
The special "user" name PUBLIC can be used to grant a privilege to every user on the system. Writing ALL in place of a specific privilege grants all privileges that are relevant for the object type.
To revoke a privilege, use the fittingly named REVOKE command:
REVOKE ALL ON accounts FROM PUBLIC;
The special privileges of the object owner (i.e., the right to do DROP, GRANT, REVOKE, etc.) are always implicit in being the owner, and cannot be granted or revoked. But the object owner can choose to revoke his own ordinary privileges, for example to make a table read-only for himself as well as others.
Ordinarily, only the object's owner (or a superuser) can grant or revoke privileges on an object. However, it is possible to grant a privilege "with grant option", which gives the recipient the right to grant it in turn to others. If the grant option is subsequently revoked then all who received the privilege from that recipient (directly or through a chain of grants) will lose the privilege. For details see the GRANT and REVOKE reference pages.