Exclude options based on already chosen options

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May 6th, 2008, 02:07 PM

orbitalx

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Exclude options based on already chosen options

I have two tables

Code:

+-------------+------------------+------+-----+---------+----------------+
| Field       | Type             | Null | Key | Default | Extra          |
+-------------+------------------+------+-----+---------+----------------+
| id          | int(11) unsigned | NO   | PRI | NULL    | auto_increment | 
| description | varchar(255)     | NO   |     |         |                | 
+-------------+------------------+------+-----+---------+----------------+

Code:

+-------------+------------------+------+-----+---------+----------------+
| Field       | Type             | Null | Key | Default | Extra          |
+-------------+------------------+------+-----+---------+----------------+
| id          | int(11) unsigned | NO   | PRI | NULL    | auto_increment | 
| description | varchar(255)     | NO   |     |         |                | 
+-------------+------------------+------+-----+---------+----------------+

joined in a many to many relationship by table:

Code:

+------------------+------------------+------+-----+---------+-------+
| Field            | Type             | Null | Key | Default | Extra |
+------------------+------------------+------+-----+---------+-------+
| lane_id          | int(11) unsigned | NO   | PRI |         |       | 
| configuration_id | int(11) unsigned | NO   | PRI |         |       | 
+------------------+------------------+------+-----+---------+-------+

what I need to do is exclude certain items from the configuration table based on other selected configurations.

for example:

the lanes table holds the following rows:

Code:

+----+-------------+
| id | description |
+----+-------------+
|  1 | Lane 1      | 
|  2 | Lane 2      | 
|  3 | Lane 3      | 
|  4 | Lane 4      | 
+----+-------------+

the configuration table contains:

Code:

+----+------------------+
| id | description      |
+----+------------------+
|  1 | Lanes 2, 3 and 4 | 
|  2 | Lanes 3 and 4    | 
|  3 | Lane 1           | 
|  4 | Lane 2           | 
|  5 | Lane 3           | 
|  6 | Lane 4           | 
+----+------------------+

and the join table contains the appropriate links to create the described relationships.

this is a reservation system, so if, for example, configuration 2 is reserved that would automatically exclude configurations 1, 2, 5 and 6.

I've accomplished this with PHP code, but I feel it would be better and more efficient with SQL.

1. am i right?
2. i'm not an SQL expert so if someone could instruct me on how to do it that would be great.

thanks,
josh

May 7th, 2008, 05:32 AM

r937

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there are two things i don't understand about your statement of the problem

1. "what I need to do is exclude certain items from the configuration table based on other selected configurations"

what does "exclude from" mean? you want to DELETE rows in the config table?

2. "if, for example, configuration 2 is reserved that would automatically exclude configurations 1, 2, 5 and 6."

assuming configuration 2 is linked via the many-to-many table, what does "exclude from" mean here? you want to SELECT lanes but not include configurations that are not linked?

this confusion probably explains why no one has answered your question so far...

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May 7th, 2008, 10:44 AM

orbitalx

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Join Date: Sep 2007

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hmm... I didn't think of that... sorry.

All of the "exclusion" I am talking about is related to SELECT statements. So using the example below, if configuration 2 is reserved (which is handled by another table, but not relevant to the question) I want to be able to perform a select to retrieve open lanes. Since configuration 2 contains lanes 3 and 4, all other configurations that contain one or both of those should not be included in the results of the select.

if that does not make sense let me know.

Thanks,
josh

May 7th, 2008, 02:17 PM

r937

SQL Consultant

Join Date: Feb 2003

Location: Toronto Canada

Posts: 16,727

Time spent in forums: 1 Month 3 Weeks 2 Days 19 h 22 m 42 sec
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Quote:

Originally Posted by orbitalx

I want to be able to perform a select to retrieve open lanes.

Code:

SELECT lanes.id
     , lanes,description 
  FROM lanes
LEFT OUTER
  JOIN reservations
    ON reservations.lane_id = lanes.id
 WHERE reservations.lane_id IS NULL

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