New answers tagged application-design
How about using a scheduled job to take a snap-shot of your users' weight stats and influencing factors into a different (could be a temp-) table, then using those to calculate the new weight (into a different column of that same table). And then update your user table with the complete set of calculated weight stats. You'd avoid all kinds of conflicts ...
Get yourself a good data model pattern book. Accept the fact that most relationships are many-to-many. Read up on table inheritance and the Party/Party Role model. Some starting points: An order has many line items, which belong to a product A product will probably belong to multiple categories A product will likely have more than one artist
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