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Re: Storing multiple items in one MySQL field?

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On Jan 10, 2012, at 10:49 PM, Karl DeSaulniers wrote:


On Jan 10, 2012, at 9:30 AM, B. Aerts wrote:

On 08/01/12 23:35, Karl DeSaulniers wrote:

On Jan 8, 2012, at 10:36 AM, Bastien wrote:



On 2012-01-08, at 7:27 AM, Niel Archer <not@xxxxxxxxxx> wrote:


--
Niel Archer
niel.archer (at) blueyonder.co.uk
Hello phpers and sqlheads,
If you have a moment, I have a question.

INTRO:
I am trying to set up categories for a web site.
Each item can belong to more than one category.

IE: Mens, T-Shirts, Long Sleeve Shirts, etc.. etc..
(Sorry no fancy box drawing)

QUESTION:
My question is what would the best way be to store this in one MySQL
field and how would I read and write with PHP to that field?
I have thought of enum() but not on the forefront of what that
actually does and what it is best used for.
I just know its a type of field that can have multiple items in it.
Not sure if its what I need.

REASON:
I just want to be able to query the database with multiple category
ID's and it check this field and report back if that category is
present or if there are multiple present.
Maybe return as a list or an array? I would like to stay away from
creating multiple fields in my table for this.

Have you considered separate tables? Store the categories in one table and use a third to store the item and category combination, one row per item,category combo. This is a common pattern to manage such situations.

NOTE:
The categories are retrieved as a number FYI.

Any help/code would be greatly appreciated.
But a link does just fine for me.

Best Regards,

Karl DeSaulniers
Design Drumm
http://designdrumm.com

Hope your all enjoying your 2012!


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Neil's solution is the best. Storing a comma separated list will
involve using a LIKE search to find your categories. This will result
in a full table scan and will be slow when your tables get bigger.
Storing them in a join table as Neil suggested removes the need for a
like search an will be faster

Bastien
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Thanks guys for the responses. So.. what your saying if I understand
correctly.
Have the categories in one table all in separate fields.
Than have a the products table. Than have a third table that stores say
a product id
and all the individual categories for that product in that table as
separate fields associated with that product id?

Am I close? Sounds like a good situation, but I didn't want to really
create a new table.
One product will probably have no more than 3 combinations of
categories. So not sure it this is necessary.

EG:

Tshirts = 1
Jackets = 2
etc..

Mens = 12
Womens = 13

So lets say I want to find all the Mens Tshirts.. I was wanting one
field to hold the 1, 12

hope that clarifies

Karl DeSaulniers
Design Drumm
http://designdrumm.com


Hi Karl,

if you don't want to do with the third-table-solution, how about an assembler-style bit-wise OR of all categories ?

constant TSHIRTS = 1 ;  // 2 to the 0th power
constant JACKETS = 2 ;  // 2 to the 1st power
constant MENS    = 8 ;  // 2 to the 3rd power
constant WOMENS  = 16 ; // 2 to the girl power :-)

INSERT INTO TABLE t_myTable ( ID, categoryField)
VALUES ( myNewId, TSHIRTS | MENS ) ;

SELECT ID
FROM t_myTable
WHERE  ( categoryField && ( TSHIRTS | MENS )) > 0 ;

This assumes that your number of categories is not that big of course, as you're limited to 64 bits/categories on a modern machine.

Bert

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Hi Bert,
Thanks for the response. I did consider that, but there may be more than 64 categories. So I am thinking that may not be best for my situation. I am actually at the same point again, but
this time with the colors. I have multiple colors for each tshirt.
I dont want to put all the separate colors as their own fields and there is an image associated with those colors too.
I'd also like to not put those all in separate fields if I can.

What's the best way to store multiple values that may change from time to time?
What kind of field?

IE:
('red.png', 'green.png', 'blue.png')

SET()
enum()
blob()
varchar()

???
TIA

Karl DeSaulniers
Design Drumm
http://designdrumm.com


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I am thinking of limiting the colors to 10 for now (after all there are only so many ways to die a shirt. =) and using a comma delimited list of abbreviated color names as a varchar string.
Then read out that string, explode on the commas and put in an array.

`pd_color` varchar(39) CHARACTER SET utf8 NOT NULL DEFAULT 'Blk,Wht,Gry,Tan,Nvy,Red,Grn,Yel,Org,Trq'

With this I can dynamically call each different color file dependent on what's in the $colors[] array.
...
$colors['Blk,Wht,Gry']
foreach($colors as $color) {
... get color for this iteration
$product = "Mens_Sample_".$color."_T.png"; //for eg.
...
$image = "http://somewhere.com/images/products/".$product;

and if I want to add colors, I can just change it to how ever many more characters + commas.

ALTER TABLE... `pd_color` varchar(55) CHARACTER SET utf8 NOT NULL DEFAULT 'Blk,Wht,Gry,Tan,Nvy,Red,Grn,Yel,Org,Trq,Brk,Ptr,Sil,Tie'

My thoughts are because it will be a string, it will be read by php out of MySQL fairly quickly and then php does the rest. Am I headed for a headache or is this unconventional but OK or is this the way to go?

Best,

Karl DeSaulniers
Design Drumm
http://designdrumm.com



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