Updates to the data 1 add a tuple 2 delete a tuple 3 modify the values of some

Updates to the data 1 add a tuple 2 delete a tuple 3

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Updates to the data: 1) add a tuple 2) delete a tuple 3) modify the values of some attributes in a tuple Updates to the data happen very frequently. Updates to the schema: relatively rare. Rather painful. Why ?
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14 Schemas and Instances Analogy with programming languages: – Schema = type/class – Instance = value/instance Important distinction: – Database Schema = stable over long periods of time – Database Instance = changes constantly, as data is inserted/updated/deleted
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15 How should we talk about relations (that is, represent them)?
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