vaibhav Tyagi

 Profile Answers by vaibhav Tyagi Questions by vaibhav Tyagi

• Oct 21st, 2007

 

ROWLOCK
Use row-level locks when reading or modifying data.

PAGLOCK
Use page-level locks when reading or modifying data.

TABLOCK
Use a table lock when reading or modifying data.

DBLOCK
Use a database lock when reading or modifying data.

UPDLOCK
UPDLOCK reads data without blocking other readers, and update it later with the assurance that the data has not changed since last read.

XLOCK
Use exclusive locks instead of shared locks while reading a table, and use hold locks until the end of the statement or transaction.

HOLDLOCK
Use a hold lock to hold a lock until completion of the transaction, instead of releasing the lock as soon as the required table, row, or data page is no longer required.

NOLOCK
This does not lock any object. This is the default for SELECT operations. It does not apply to INSERT, UPDATE, and DELETE statements.

Example:

SELECT OrderID
FROM Orders (WITH ROWLOCK)
WHERE OrderID BETWEEN 100 AND 2000

UPDATE Products (WITH NOLOCK)
SET ProductCat = 'Machine'

WHERE ProductSubCat = 'Mac'