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i genuinely cannot think of a single instance where you would want to delete one entry, and replace it with a reference to another
Well, there’s not always a benefit to keeping historical data. Sometimes you only want the most up-to-date information in a particular table or database, so you’d just update the row (replace). It depends on the use case of a given table.
what elon is implying here (remove “duplicate” entries, however that’s supposed to work)
Elon believes that each row in a table should be unique based on the SSN only, so a given SSN should appear only once with the person’s name and details on it. Yes, it’s an extremely dumb idea, but he’s a famously stupid person.
Presumably, they also fired the staff who know how to look that information up