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A comment on Things I wished more developers knew about databases. Parent comment

Re:Things I wished more developers knew about databases by btilly on Wednesday April 22, 2020 @12:42PM (#22947481)
No, left joins were intended here. They mean different things.

With inner joins the semantics are the same. If the performance is different, the database query optimizer is broken.

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Re:Things I wished more developers knew about databases by gtsteve on Thursday April 23, 2020 @07:10AM (#22954709)
I see, apologies.

However, I'm reasonably certain we'd see poor performance with that query on MySQL 5.7, but I don't think it's got as good an optimiser as Postgres for example.

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Re:Things I wished more developers knew about databases by btilly on Thursday April 23, 2020 @05:06PM (#22961429)
I can't say that MySQL doesn't perform poorly. But if so, then their optimizer is more broken than I though.

Even SQLite figures this one out and does it right.

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