Sql Transaction Isolation Level

Controls the locking and row versioning behavior of Transact-SQL statements issued by a connection to SQL Server.

SET TRANSACTION ISOLATION LEVEL
{ READ UNCOMMITTED
| READ COMMITTED
| REPEATABLE READ
| SNAPSHOT
| SERIALIZABLE
}
[ ; ]

READ UNCOMMITTED
Specifies that statements can read rows that have been modified by other transactions but not yet committed.

READ COMMITTED
Specifies that statements cannot read data that has been modified but not committed by other transactions. This prevents dirty reads.

REPEATABLE READ
Specifies that statements cannot read data that has been modified but not yet committed by other transactions and that no other transactions can modify data that has been read by the current transaction until the current transaction completes.

SNAPSHOT
Specifies that data read by any statement in a transaction will be the transactionally consistent version of the data that existed at the start of the transaction.

SERIALIZABLE

Specifies the following:

* Statements cannot read data that has been modified but not yet committed by other transactions.
* No other transactions can modify data that has been read by the current transaction until the current transaction completes.
* Other transactions cannot insert new rows with key values that would fall in the range of keys read by any statements in the current transaction until the current transaction completes.