I cannot really understand the example from https://www.postgresql.org/docs/9.1/static/explicit-locking.html
where they embed the lock along with the SELECT clause
SELECT pg_advisory_lock(id) FROM foo WHERE id = 12345; -- ok
What is it selecting from FOO? I would understand better if it is like
SELECT pg_advisory_lock(123); //lock
SELECT * FROM foo WHERE id = 12345;
where it is explicitly locking the block. I can't seem to find explanation on how to really use advisory lock anywhere that explains the differnece between both Embedding and Explicitly on its own statement.