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Re: Qualifier involving many-to-many relationship
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Re: Qualifier involving many-to-many relationship


  • Subject: Re: Qualifier involving many-to-many relationship
  • From: Paul Hoadley <email@hidden>
  • Date: Thu, 29 Jan 2015 14:52:07 +1030

Hi Aaron,

On 29 Jan 2015, at 2:04 pm, Aaron Rosenzweig <email@hidden> wrote:

When you turn on the SQL adaptor debugging it will become clear what it is doing wrong. Then you’ll go “duh!"

The generated SQL is:

SELECT t0.id, t0.id_no, t0.user_id FROM teacher t0 INNER JOIN connection T1 ON t0.id = T1.teacher_id WHERE not (T1.school_id = 1);

(where I've manually substituted the bindings).  What I think I need is something like this:

SELECT t0.id, t0.id_no, t0.user_id FROM teacher t0 WHERE NOT EXISTS (SELECT 1 FROM connection e0 WHERE e0.teacher_id = t0.id AND e0.school_id = 1);

Here’s the full reason why:
http://www.chatnbike.com/presentation_existsQualifier/

Just re-read that for the tenth time!

So, here’s my recommendation:

1) Make your “Connection” entity have a single integer primary key. Do not have a compound PK.

Is a compound PK going to prevent ERXExistsQualifier working in a case like this?  I can make the change, just wondering why.

2) Use ERXExistsQualifier.

It should do the trick :-)

I'm trying... can you push me along a little bit based on the desired SQL above?


-- 
Paul Hoadley
http://logicsquad.net/


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 >Re: Qualifier involving many-to-many relationship (From: Aaron Rosenzweig <email@hidden>)

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