SearchOracle expert Rudy Limeback has published an excellent
overview of the SQL-99 OUTER JOIN syntax, and explain how the
new syntax compares to the older (+) outer join notation::
An OUTER join returns all rows from one table, plus matching
rows,
if any, based on the join condition, from the other
table. There are three types of OUTER joins. LEFT OUTER joins
and RIGHT OUTER joins are identical, and the difference is
entirely based on which table you mention first. So the
following two queries will both return the
same
results:
select columns
from table1
left outer
join table2
on table1.id = table2.t1_id
select columns
from table2
right outer
join table1
on table2.t1_id = table1.id
Important: make sure you understand why the
above two queries are identical. Note which table is named first
in the FROM clause.
