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  • Chia Ming Liang thinks this is interesting:

When a relational database performs an update it has to maintain a copy of all of the original values in some place to ensure isolated transactions. A single UPDATE statement might involve thousands of rows and might take several minutes to complete. If there were a failure during the update (if someone switched off the computer, for example), the system is guaranteed to roll back and none of the changes will be committed.


Cover of SQL Hacks


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