Advise on Data structure , Many Sub Categories

I've created a db, though i spent  time on planning the structure,
i ended up with a lot and i mean  A LOT, of progamming to do afterwords...

I want to redo the whole DB and could really use some advise.
This is a product Database:

Part No: PK123

Length: 20cm

Categories: Currently have 3 but will expand to more probably 1-2 per year
Type: anywhere from 3 to 12 types per categorie
Brand: a few hundred per categorie
Part No: already at 100,000 to 1 mil  per category

Now what i did is crossed my findgers and hoped i could handle the programming afterwords:
Category (ID, Category)
Brand (ID, Brand, ....)
Part No ( ID , [Category ID] , [Brand ID], [Part No])

Description_Names ( ID, [Desc Name]) * lenght, meterial , Note , Etc..
Description (ID, [Part No ID] , [Desc Name ID], Value)  * 20 cm, semi Metalic, etc..

In the description i stored everithing, Sizes, Material, etc...

My biggest problem is that every Type (not category) has its own description Fields,
some are same Unique and some are same, for example all have lenght , but only 2 Types have diameter.
Who is Participating?
hnasrConnect With a Mentor Commented:
You are in the field of normalization!
Search for Data Normalization.
CMDAIAuthor Commented:
sorry lots of typo's

Thank's for the article,
even though i worked thorugh normalization already,
it helped me review and realize my actuall problem...

I have this data:
[Item , Type]             || [Description]
[PK112 , Brake pad]  ||   [size,width,lenght]
[PK113 , AirCon Filter]  ||  [, Inner DiameOuter diameterter , Height, Rim Width]

Now i cant figure out how to biuld a relationship, for 'every type' has its own description table....

Table:[Items]'' Related to only one of the description table
Table:[Metalic Pad Description]
Table:[Aircon Filter Description]
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CMDAIAuthor Commented:
Denormalized Table Overview:
|| Item || type || A______ || B_____  || C_____
|| PK1 ||   A   ||2cm;oval  || NULL       || NULL      
|| PK2 ||   B   || NULL       || 1cm;2cm || NULL      
|| PK3 ||   A   ||3cm; cone|| NULL       || NULL      
|| PK4 ||   C   || NULL       || NULL       || Metalic,4pc;3cm
CMDAIAuthor Commented:
I Draw a pic af what i'm trying to solve
CMDAIAuthor Commented:
Comments i posted above, "irrelevant"
I asked admin if i could delete them...

anyway here is a siplified version of wat i came to after normalization.

Main Table: ITEMS
Many smaller tables: names as types of items with one to one relationship to items table.

How to 'control' or 'make sure' that one item only has one description in one table?
(or none ofcourse)

PS* The fild name "TYPE" is a db look up of all the description table names.

CMDAIAuthor Commented:
Thanks alot!
feel so Depressed & Happy, i should leaned this ages ago
"Super/Subtypes" ;)
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