How to query based on multiple relations between columns - MySQL? - php

Question

I have four columns in a properties table: property_id, value, id, material_id.
I also have an array of properties: Array $properties
The schema is a bit complicated, because I want to find the material_id based on the matching properties.
An example:
$properties = array(['property_id'=>1,'value'=>3],['property_id'=>2,'value'=>6],['property_id'=>3,'value'=>4]);
Example table output:
+----+-------------+-------------+-------+
| id | material_id | property_id | value |
+----+-------------+-------------+-------+
| 1 | 1 | 3 | 5 |
| 2 | 1 | 3 | 5 |
| 3 | 1 | 3 | 5 |
| 4 | 2 | 1 | 3 |
| 5 | 2 | 2 | 6 |
| 6 | 2 | 3 | 4 |
| 10 | 4 | 1 | 9 |
| 11 | 4 | 2 | 3 |
| 12 | 4 | 3 | 6 |
+----+-------------+-------------+-------+
Now, I need material_id that satisfies all the properties. How can I do that..? Do I need to use exist statement of MySQL?

Answer 1

Now, for each element in your array you will want to run a statement that looks like this:
SELECT material_id FROM properties WHERE property_id = 2 AND value = 3;
Do you need help on the php code also? You could run a for each loop, but I will need to know what way you are using to communicate with your database for more specifics.
edit
foreach ($properties as $foo => $bar)
{
$sql = 'SELECT material_id FROM properties WHERE ';
foreach ($bar as $key => $value)
{
$sql .= $key .' = '. $value .' AND ';
}
$sql .= 'true';
*run your PDO code on $sql here*
}

Answer 2

On behalf of performance, it's not a good idea to run a query per array's value. If you have an oversized array things can get pretty slower.
So, best solution can be to build a single query including all conditions presented on $properties array:
<?php
$properties = array(['property_id'=>1,'value'=>3],['property_id'=>2,'value'=>6],['property_id'=>3,'value'=>4]);
$qCondition = [];
foreach($properties as $prop) {
$q = sprintf("(property_id = %d AND value = %d)", $prop["property_id"], $prop["value"]);
$qCondition[] = $q;
}
// assuming that your database table name is 'materials'
$sql = sprintf("SELECT * FROM materials WHERE (" . implode(" OR ", $qCondition) . ")");
echo $sql;
Result:
SELECT * FROM materials
WHERE ((property_id = 1 AND value = 3) OR (property_id = 2 AND value = 6) OR (property_id = 3 AND value = 4))
Therefore, you need to run only one single query to get all desired rows.
You can play with suggested solution here: http://ideone.com/kaE4sw