postgresql - SQL Retrieve rows that have all rows from other table -

i facing issues retrieving data using sql in 1 specific scenario:

suppose have following tables:

• a (id, attr_a, attr_b);
• b (id, attr_d, attr_e);
• c (id_a, id_b);

as can see, table c have fk referencing id table a, , referencing id table c.

i need retrieve table a rows each a row relates every b row.

in real life scenario, assuming a means users, b means privileges, , c many many entity relates users privileges, want users have privileges

select a.* join c on id_a = id group id having count(id) = (select count(*) b) 

there no need use subquery because a.id primary key (or unique @ least) column referenced c.id_a.