LOCK IN SHARE MODE should be used...

The correct answer is B. When you need a lock that allows other transactions to read the same data, but not update or. With LOCK IN SHARE MODE, InnoDB locks each selected row with a shared lock. Other transactions can still read the selected rows, but cannot update or delete them until the first transaction releases the locks, which happens when the transaction finishes. Also, if the SELECT…

Transactions and Locking

Question

Options

AWhen you need a lock that does not allow other transactions to read, update or delete the same
BWhen you need a lock that allows other transactions to read the same data, but not update or
CWhen you need a lock that allows other transactions to read, update and delete the same locked

How the community answered

(27 responses)

A
7% (2)
B
78% (21)
C
15% (4)

Explanation

With LOCK IN SHARE MODE, InnoDB locks each selected row with a shared lock. Other transactions can still read the selected rows, but cannot update or delete them until the first transaction releases the locks, which happens when the transaction finishes. Also, if the SELECT will select rows that have been modified in an uncommitted transaction, IN SHARE MODE will cause the SELECT to block until that transaction commits.

Topics

#LOCK IN SHARE MODE#shared locks#transaction locking#SELECT locking

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