SQL left outer join question

Sometime ago a number of users gave me some code and help to do a SQL
left outer join on Paradox 5 tables.

i would like to know how one can do a left outer join on the primary
index of two tables where the primary index consists of 3 datafields. The
examples I got was only for a join on one field.

Can one do a join on more than one field ? If so, what is the syntax ?

Thank You

Tian Olivier
SABC : TV News