Notes on SQL

Random articles from a puzzled DBA

In a previous article (here) I described how the isolation level read committed works, with some examples. There is also an optimistic version of this – read committed snapshot, which uses row versions. The behaviour of read committed and read committed snapshot is similar and repeating the examples used previously will show the similarities and …

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The previous articles on isolation levels were using pessimistic locking. Two further isolation levels exist that use optimistic locking and are row-versioning based. Snapshot Isolation With snapshot isolation level no locks are placed upon the data when it is read and transactions that write data don’t block snapshot isolation transactions from reading data. Instead, when …

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