How do I populate a database from a number grid in mysql?

[Q695]

I don't want to use AI, or a primary key to sort the data, as it could create some problems if the items are visited out of order, but I want to sort it always based upon a single element for speed.

 

I'm creating a table that will be populated (built), when it's corresponding entry doesn't exist, how do I get it sorted out if someone visits 2, then 7 before they visit 5 to read what's there?  It's not a 2d number line, but a 3d number grid.