showing multiple REFERENCE details of id fields in single query that share the same table

From: Ferindo Middleton Jr <fmiddleton(at)verizon(dot)net>
To: pgsql-sql(at)postgresql(dot)org
Subject: showing multiple REFERENCE details of id fields in single query that share the same table
Date: 2005-09-15 01:11:37
Message-ID: 4328CA49.7030409@verizon.net
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I have a table which has two id fields which REFERENCE data back at
another table. It's setup like this:

class_prerequisite_bindings(id SERIAL, class_id INTEGER REFERENCES
classes(id), prerequisite INTEGER REFERENCES classes(id))

The classes table is like this:
classes(id SERIAL, course_title TEXT, course_code TEXT)

I have the following query:
SELECT * FROM class_prerequisite_bindings, classes WHERE
class_prerequisite_bindings.class_id = 64 AND
class_prerequisite_bindings.class_id = classes.id;

If I run the query above, the result will only give me info about the
class_id field matching id 64 back in the classes table. PROBLEM: I want
this query to also show the info about the prerequisite field which
would also have info at the classes table. This query will only show the
course_title and course_code of the class_id but I need this for the
prerequisite field as well. I think I need to do a JOIN, but I don't
understand how. How can I do this?

Ferindo

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