Microsoft® SQL Server 2012 Unleashed

Read Uncommitted Isolation

If you set the Read Uncommitted mode for a session, no isolation is provided to the SELECT queries in that session. A transaction that is running with this isolation level is not immune to dirty reads, nonrepeatable reads, or phantom reads.

To set the Read Uncommitted mode for a session, you run the following statements from the client:

T-SQL—Use SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED.

ODBC—Use the function call SQLSetConnectAttr with Attribute set to SQL_ATTR_TXN_ISOLATION and ValuePtr set to SQL_TXN_READ_UNCOMMITTED ...