Parallel Query

What Does Parallel Query Mean?

Parallel query is a method used to increase the execution speed of SQL queries by creating multiple query processes that divide the workload of a SQL statement and executing it in parallel or at the same time.


Since each process works on something different at the same time, it greatly reduces overall execution time of the SQL statement. This is very beneficial for systems with multiple CPUs that can work on the processes.

Techopedia Explains Parallel Query

A normal SQL processing without the parallel query feature is always performed by a single server process.

With the feature enabled, multiple processes are created to simultaneously work together on that single SQL statement and can dramatically improve the performance of data-intensive operations such as those in very large database systems.

Since the many processes can be split among multiple CPUs present, clustered and massively parallel systems, as well as symmetric multiprocessing systems can greatly benefit from it.

Parallel query processing occurs during the query optimization phase where the SQL server is looking for query index operations which might benefit from parallel operation.

When found, the server inserts exchange operators into the query execution plan in order to turn it into a parallel-query execution plan which can use more than one thread or process for execution.


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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…