Inconsistent analysis (unrepeatable read)

I did warn that this blog, might be used to remind myself of things: and this is one.

Inconsistent analysis is a problem with databases when an aggregate function is used on data that is being updated by another transaction eg

T1                                            T2

\alpha =SUM(accounts(4 .. 7))

account(1) = \alpha           account(4) = account(4) + 10

account(2) = \alpha + 5

By the final line \alpha is out of date (as account 4 has been updated but the SUM total has not).

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