Beginner Join question

Been out of DB programming for a while, and am trying to get back in
with postgres under Linux.

Anyway, my question (should be fairly simple, but the manuals
arn't quite clear) is as follows:

TABLE A (   TABLE B(
  record_id   record_id
  field1      field3
  field2)     field4)

record_id in both tables are the same.
The record definitely exists in TABLE A, but not
necessarily in TABLE B.

I need to get the following:

record_id | A.field1 | A.field2 | B.field3
-------------------------------------------------------------------
rec1      | xxxx     | xxxxxx   | Field displayed if there is
          |          |          | a record in B, such that A.record_id
          |          |          | is equal to B.record.id, otherwise
          |          |          | leave it blank.
-------------------------------------------------------------------

I'm going to have about a million records in each table, so
efficiency of the join is a priority. Disk space is not.

Thanks in advance.

--Calvin

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