Query plan

<p>A query plan (or query execution plan) is a sequence of steps used to <a href="/facts/Data_access/j7m1xs1U">access data</a> in a <a href="/facts/SQL/UjQLJcYm">SQL</a> <a href="/facts/Relational_database_management_system/pEKGmJLy">relational database management system</a>. This is a specific case of the <a href="/facts/Relational_model/VFf4dDIU">relational model</a> concept of access plans.
</p><p>Since <a href="/facts/SQL/UjQLJcYm">SQL</a> is <a href="/facts/Declarative_programming/gogtdzcJ">declarative</a>, there are typically many alternative ways to execute a given query, with widely varying performance. When a <a href="/facts/Information_retrieval/MFSmpeNw">query</a> is submitted to the database, the <a href="/facts/Query_optimizer/KsSwxtw8">query optimizer</a> evaluates some of the different, correct possible plans for executing the query and returns what it considers the best option. Because query optimizers are imperfect, database users and administrators sometimes need to manually examine and tune the plans produced by the optimizer to get better performance.
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Query plan open-in-new

Query plan