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Databases & SQL vocabulary · Transactions and Concurrency

Lock

Meaning in databases & SQL, with examples

/lɑːk/nounCommon term

In databases & SQL, lock means: A mark the database places on a row, page or table so that other transactions cannot change it, or sometimes read it, until the current transaction ends.

In Turkish: kilit

How it is used

Locks can be row-level or table-level, and shared (for reading) or exclusive (for writing). People say a query 'takes', 'holds', 'waits for' or 'releases' a lock. Long-held locks cause blocking and timeouts, so DBAs monitor lock waits closely.

Example sentences

  1. The batch job holds a lock on the inventory table for almost a minute.

  2. Use SELECT ... FOR UPDATE to lock the row before you change the balance.

Common collocations

  • hold a lock
  • release a lock
  • row-level lock
  • lock wait
  • lock timeout
  • deadlockA situation where two or more transactions each wait for a lock the other holds, so none of them can continue until the database cancels one.
  • transactionA group of database operations that are treated as one unit: either all of them succeed together or none of them is applied.
  • isolation levelA setting that controls how much one transaction can see of other transactions' changes, trading data safety against speed and concurrency.
  • ALTER TABLEThe SQL statement that changes the structure of an existing table, for example to add, rename or drop a column or to add a constraint.

This word in other fields

The same English word can have a different meaning in another field:

More terms: Transactions and Concurrency

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