Query optimization is the process of improving the speed of a database query, or the execution of a query, in order to improve the performance of a computer application. This process is commonly performed on databases, although it can be used to optimize the execution of other types of queries.
Query optimization typically involves ensuring that the query is written efficiently, with the use of suitable indices, metadata and other data structures to improve the execution time of the query. It can also involve the optimization of hardware and/or software components to maximize the customers satisfaction.
The optimization of a query is usually performed as a method of cost reduction, by making the query more efficient and therefore reducing the time and/or resources required for its execution. It is a technique that is employed by database and query administrators and developers in order to ensure optimal performance.
In its most basic form, query optimization involves restructuring the query by replacing a non-optimized query with one that is written using more efficient SQL code. This involves replacing the inefficient sub-queries with joins, or other clauses or expressions which require fewer core resources to execute the query. Other optimizations can also include the use of hints or indices to speed up the query, as well as the use of probabilistic algorithms to generate more accurate query plans.
In more advanced level optimization techniques, the query may be analyzed and modified to make use of more efficient data sources or join types. The data sources used in the query may be rearranged to make use of indexes, materialized views, or other data structures that can greatly reduce the execution time of the query. The query can also be adjusted to make use of more efficient join types, such as hash joins or sort-merge joins.
Query optimization is an important tool in the development and administration of applications on large databases. It can help improve the performance of applications, reduce overhead and resource consumption, and ensure that applications are performing optimally and quickly. With proper query optimization, applications can be made to run faster, more efficiently, and cost less to maintain.
