What are hints used for in SQL queries?
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Then, what are query hints in SQL Server?
Hints are options or strategies specified for enforcement by the SQL Server query processor on SELECT, INSERT, UPDATE, or DELETE statements. The hints override any execution plan the query optimizer might select for a query.
Similarly, what is the use of Nolock in SQL? The NOLOCK hint allows SQL to read data from tables by ignoring any locks and therefore not being blocked by other processes. This can improve query performance, but also introduces the possibility of dirty reads. Read more to better understand the use of NOLOCK.
Consequently, how do you query hints?
Query hints specify that the indicated hints should be used throughout the query. They affect all operators in the statement. If UNION is involved in the main query, only the last query involving a UNION operation can have the OPTION clause. Query hints are specified as part of the OPTION clause.
Which hints is used to control the locking mechanism of tables?
Table Hint. This hint is used when certain kind of locking mechanism of tables has to be controlled. SQL Server query optimizer always puts the appropriate kind of lock on tables, when any of the Transact SQL operations SELECT , UPDATE , DELETE , INSERT or MERGE are used.