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Asked: 2026-05-10T23:01:58+00:00

I have a relationship between two tables, authors and styles. Every author is associated

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I have a relationship between two tables, authors and styles. Every author is associated with a style, with the special case where an author doesn’t have a style (IS NULL).

There’s no problem in setting the reference to NULL, but there’s a problem doing a query to select the authors and styles.

For example, the query: 

SELECT 'authors'.'id', 'authors'.'name', 'styles'.'name', 'authors'.'comments' FROM  'authors' , 'styles' WHERE 'authors'.'style' = 'styles'.'id'

just ignores the authors that have a NULL style (as expected).

I need to do a select that also lists authors with NULL style, like a left join would do (I can’t use LEFT JOIN fo some reasons).

There’s a solution that doesn’t include explicit joins?

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1 Answer

  1. The most obvious solution is a LEFT OUTER JOIN.

    See: http://www.postgresql.org/docs/8.1/static/tutorial-join.html

    If you don’t want to use explicit joins you should be able to use a UNION

    SELECT 'authors'.'id', 'authors'.'name', 'styles'.'name', 'authors'.'comments' FROM  'authors' , 'styles' WHERE 'authors'.'style' = 'styles'.'id' UNION SELECT 'authors'.'id', 'authors'.'name', '', 'authors'.'comments' FROM  'authors' WHERE 'authors'.'style' IS NULL
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