Isolation levels12-03-isolation-levels.mp4amazon12-03-q16
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The update command in T1 can update the values in either order, and the select command in T2 can compute the average at any point before, between, or after the updates.
12-03-q26
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T2 could return avg(A) computed before T1 and avg(B) computed after T1.
12-03-q36
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In all scenarios, R values are increased before S values, and avg(A) is computed before avg(B).
12-03-q46
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T2 must (appear to) execute entirely before or after T1. You might think T2 could (appear to) execute between T1's two statements since the second statement is an insert, but that would be allowing dirty reads.