The ItemID is something that is critical to the way RetailEdge works. The itemID is a 6 digit code that RetailEdge uses for a number of reasons. So when creating SKUs in RetailEdge you should either use a alphanumeric code or use a code that is less than or greater than 6 digits. RetailEdge will allow you to use a 6 digit SKU, but you need to be aware that if a 6 digit SKU is used, an item number might get created that will match an Item ID. On the RetailEdge Sales Screen if a 6 digit number is entered and there is an ItemID and SKU that match, the ItemID will trump the SKU in the lookup.
1. The 6 digits allows for 1M items in inventory (000001 - 999999).
2. The item numbers have to be an even number of characters because some of the compressed barcodes we use have to have even number of characters. We could go to 8 but then we might start bumping into some of the standard codes (UPCE 7 digits, EAN13, UPC12, etc.).
3. We need the ItemID to be short because it is the value that is used for the barcodes on the barcode labels and tags we print. Since our SKUs allow 50 characters we can't use this value. In addition the numeric value is printed on most tags because if the barcode does not scan a clerk can simply type in a 6 digit number on the numeric keypad found on most keyboards and enter the items into the sale.
This allows people who want to use numeric values for SKUs for other reasons to use any value from 1 up to 99,999 (zero is reserved for non-entered items). This can be useful for people who want to block inventory items into discrete chunks. For instance, if I want a quick way to enter a department SKU, I could create items with SKUs 1-10 that might represent my different departments. Or if I had a series of rental items that I always sold, I could number them 21-29. Then the clerk could then just enter a two digit number and be able to sell a particular item which should be pretty easy to remember.
Sounds a little like a justification, but it should give you some of the thought process behind the 6 digit numbering. We typically tell users not to use SKUs that are numeric only, because they don't mean much to a user looking at them. They can also build in useful information like size, vendor codes, date codes, etc. when you use non-numeric codes. But as people start using manufacturers that use UPCs we find more people using numeric codes for convenience.