Re: Finding broken links

[Felix Geerinckx]

Jos Elkink wrote:

> When I use foreign keys in a table and I want to check which ones are referring to entries that do
> not exist anymore, how could I do this?

You can use the InnoDB storage engine and enforce referential integrity from the start.

> How do I get exactly the opposite subset, only those where locations.id
> indeed does not exist? (So I can repair these inconsistencies in my database.)

You will need to use either a subquery or a LEFT OUTER JOIN.
See http://dev.mysql.com/doc/mysql/en/rewriting-subqueries.html for examples.

--
felix
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