Outer Joins Graphically
December 30th, 2009
Outer Joins
If English and French both have a unique key on the “ordinal_id” then it’s basically one-to-one relationship
We add an arrow in the middle of the line to denote “outer join”. The arrow points from the table that drives the join, ie all the rows in the table pointed from are returned even if a match isn’t found in the table pointed to.
idea for the above graphic came from http://blog.mclaughlinsoftware.com/wp-content/uploads/2009/02/joinmapping.png which was originally posted on http://blog.mclaughlinsoftware.com/oracle-sql-programming/basic-sql-join-semantics/
| type | ANSI | ANSI 89 (Oracle) | type | type | |
| inner join | english INNER JOIN french using (ordinal_id) |
english e, french f where e.ordinal_id=f.ordinal_id |
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| left outer join | english LEFT JOIN french using (ordinal_id) |
english e, french f where e.ordinal_id=f.ordinal_id(+) |
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| right outer join | english RIGHT JOIN french using (ordinal_id) |
english e, french f where e.ordinal_id(+)=f.ordinal_id |
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| full join | english FULL JOIN french using (ordinal_id) |
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Outer Join Query Examples
Oracle L
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