medium10 pts · first answer countsdatabasestransactionslocking

FOR UPDATE that locks nothing useful

Code runs `SELECT ... FOR UPDATE` and then a separate UPDATE, using an autocommit connection with no BEGIN. Two requests still overwrite each other. Why?

A.FOR UPDATE only works on tables without indexesB.FOR UPDATE needs the NOWAIT option to lockC.Each statement commits alone, so the lock ends at onceD.UPDATE statements ignore all row locks

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FOR UPDATE that locks nothing useful

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