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Asked: 2026-05-10T13:34:20+00:00

When I’m joining three or more tables together by a common column, I’d write

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When I’m joining three or more tables together by a common column, I’d write my query like this:

SELECT * FROM   a, b, c WHERE  a.id = b.id AND    b.id = c.id

a colleague recently asked my why I didn’t do explicit Join Transitive Closure in my queries like this:

SELECT * FROM   a, b, c WHERE  a.id = b.id AND    b.id = c.id AND    c.id = a.id

are the really any advantages to this? Surely the optimiser can imply this for itself?

edit: I know it’s evil syntax, but it’s a quick and dirty example of legitimate legacy code +1 @Stu for cleaning it up

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  1. You don’t need to do this in todays database engines, but there was a time when things like that would give the query optimizer more hints as to possible index paths and thus to speedier results.

    These days that entire syntax is going out anyway.

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