Many-to-many SQL Query - Dev Articles

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January 25th, 2006, 02:38 PM

markanimations

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Many-to-many SQL Query

I have created a many-to-many database...

Code:

Categories    Company       Join_Cat
---------     ---------     --------
Cat_ID*       Comp_ID*      Join_ID*
Cat_Name      Comp_Name     Cat_ID
                            Comp_ID

The Join_Cat table joins the Company to various Categories.

What I am trying to do is return all Categories Names and ID that a company IS NOT listed in ...

a: I can return all Categories that Company #1 are in. e.g.

Code:

SELECT * FROM Categories
WHERE Cat_ID IN
(SELECT DISTINCT Join_Cat.Cat_ID FROM Join_Cat WHERE Join_Cat.Comp_ID = 1)

But, when I try to reverse the results to 'not equal' (<> 1) It return all Categories. I'd thought this would return all categories that company 1 are not in)

I have tried joins and Subqueries, but to no avail.

Any help would be appreciated.

SERVER MODEL:
PHP and MySQL v5

January 25th, 2006, 04:52 PM

markanimations

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Join Date: Jan 2006

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I can get it working in version 5 of MySQL, but not in version 4.0. Can anyone show me how to convert the sub-query to a JOIN?

Code:

SELECT *
FROM Categories
WHERE Cat_ID NOT IN (SELECT DISTINCT Join_Cat.Cat_ID 
FROM Join_Cat WHERE Join_Cat.Comp_ID = 1

June 28th, 2006, 08:18 PM

superduck

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Left Join?

I don't know if this will work in MySQL but it works in MS SQL 2000

SELECT cat.*
FROM Categories cat
LEFT JOIN dbo.Join_Cat jc ON cat.Cat_ID = jc.Cat_ID AND jc.Comp_ID = 1
WHERE jc.Cat_ID IS NULL

Quote:

Originally Posted by markanimations

I can get it working in version 5 of MySQL, but not in version 4.0. Can anyone show me how to convert the sub-query to a JOIN?

Code:

SELECT *
FROM Categories
WHERE Cat_ID NOT IN (SELECT DISTINCT Join_Cat.Cat_ID 
FROM Join_Cat WHERE Join_Cat.Comp_ID = 1

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