26/06/2015

[SQL] Oracle subquery in join statement

In Oracle, it's possible to use sub queries in a join statement by giving an alias to the subquery and joining on that alias:

SELECT a.column1, a.column2, c.column3
FROM a JOIN (
SELECT b.column1, b.column2, b.column3
FROM b
) c
ON (a.column1 = c.column1 AND a.column2 = c.column2)

Obviously you would never write a SIMPLE query EXACTLY as the example above, it's just to show the mechanics when you actually need to create a slightly more complex one

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