The given schedule S is:
To be view serializable W2(X) must move before R1(X) or after W1(X). However, the first would violate the "initial read" rule and the second would violate the "last write" rule.
T2 starts after T1 so has a higher timestamp. When T1 comes to write X it sees that T2's timestamp on it. By ...
For SQL Server:
But what's about single statements?
In SQL Server, there is 4 transaction isolation levels (in pessimistic locking model). Default transaction isolation level is Read Committed, and locks are placed on a statement level. If you have a transaction that has 2 statements inside it that retrieve same data, and in the middle of that ...
Serializable means that there is some order the transactions can be run in without overlapping and we'll end up with the same answers and the same state of the data base as we get by running the transactions in parallel with serializable isolation level.
Given two transactions, A and B, the only valid states of the system are
All of A followed by all of B, ...