Query for props list with or without values
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by vitto
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Published on 2010-04-29T17:37:49Z
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2010/04/29
18:27 UTC
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Hi, I'm trying to make a SELECT
on three relational tables like these ones:
table_materials
-> material_id
- material_name
table_props
-> prop_id
- prop_name
table_materials_props
- row_id
-> material_id
-> prop_id
- prop_value
On my page, I'd like to get a result like this one but i have some problem with the query:
material prop A prop B prop C prop D prop E
wood 350 NULL NULL 84 16
iron NULL 17 NULL NULL 201
copper 548 285 99 NULL NULL
so the query should return something like:
material prop_name prop_value
wood prop A 350
wood prop B NULL
wood prop C NULL
wood prop D 84
wood prop E 16
// and go on with others rows
i thought to use something like:
SELECT *
FROM table_materials AS m
INNER JOIN table_materials_props AS mp
ON m.material_id = mp.material_id
INNER JOIN table_materials_props AS p
ON mp.prop_id = p.prop_id
ORDER BY p.prop_name
the problem is the query doesn't return the NULL
values, and I need the same prop
order for all the materials
regardless of prop values are NULL or not
I hope this example is clear!
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