Why SKU's need to be unique for each product, don't we have product id for that?

Question

Question : How product nos/item number/part number different from SKU?

From what I understand, SKU groups all the attributes that applies to a product and assigns a fixed number/value to it so that that one number could define a set of values within an attribute group. For example if you were to make a stock transaction, lets say item is - Mens V neck T-Shirt and item number being MN-VN-TS now suppose this product comes in two sizes(M-L) and two colours(Grey and Blue) then the item will have four SKU's one defining each combination of attributes. SZ-M-COL-GRY, SZ-L-COL-GRY, SZ-M-COL-BLU, SZ-L-COL-BLU. So the transaction will look something like :

Received 6 pcs of Item: MN-VN-TS with SKU :SZ-L-COL-GRY

Lets now say there is another item Mens Round Neck T-Shirt with same attributes item name being MN-RN-TS so transaction should appear like:

Received 6 pcs of Item: MN-RN-TS with SKU :SZ-L-COL-GRY

So what you see now is that the stock of two different products got affected but the attributes were same and hence we kept SKUs also same. This way if you need to get the stock of all grey garments you can get all the SKU's having the attribute colour with the value grey and you'll get the stock of all grey coloured garments. Where as this would not be possible if different SKU was to be used for different products having same attribute group and values. It will also make the task of new item/product creation simple which is having the same attribute set. If you keep all the SKUs different for each product then it will be a very painful job to create new SKUs for every new product you add and every possible combination of attribute values even when such combinations already have SKUs defined for some other product.

So my questions is why dose the SKU needs to be unique for each product? What purpose dose it serves by being unique?

Answer 1

SKU groups all the attributes that applies to a product and assigns a fixed number/value to it so that that one number could define a set of values within an attribute group.

First of all, SKU (stock keeping unit) does not group anything. A SKU is a reference code for an item for which you keep inventory. Therefore, it must be unique; otherwise, you will not be able to keep accurate inventory for all of the items that require keeping inventory.

So what you see now is that the stock of two different products got affected but the attributes were same and hence we kept SKUs also same.

Additionally, SKUs are not attributes as you have described. Your SKUs should be MN-VN-TS-SZ-L-COL-GRY, etc. not just SZ-L-COL-GRY, etc. So, your products indeed have unique SKUs.

So my questions is why dose the SKU needs to be unique for each product? What purpose dose it serves by being unique?

Lastly, product IDs are for the system (Magento). If you were to use product IDs as your unique identifier for a product, nobody could use codes they wanted. A lot of merchants use meaningful SKU codes, as you have demonstrated. Therefore, a SKU is a one-to-one representation of a product ID that you can customize. Besides, do you really want everybody to use SKUs 1 ~ 10 to describe their first ten products?

To answer your last two questions, which are actually the same question, a SKU needs to be unique in order for you to distinguish between items and keep accurate inventory.

Answer 2

This looks like a retail stock question as apposed to magento, however using the magento platform. What I can advise is the following:

Use your SKU as the following:

ARTICLE#/COLOUR/SIZE
G58493/BLUE/XL

This will also help with warehousing, data analysis, and much more. Take a read into EAV (Entity Attribute Value) structures this may help you understand stock systems more.

Stock Keeping Unit is the value you will uniquely give to your item based on locations of warehouse etc or think of it as your personal identifier that only your own company will understand.

I personally deal with large volumes of Sportswear and have found the SKU structure above flawless.

Have a think how you want to build your data, magento will do it for you, but its down to how you want to work it.

Kind Regards Digitalyst