Execution plan (SQL)
An execution plan in Structured Query Language (SQL) is an ordered set of steps used by a relational database management system software (RDBMS) to determine the most efficient approach for executing a given SQL statement. Execution plans are created by the query optimizer, a component of the RDBMS that evaluates, executes, and optimizes SQL statements. The query optimizer uses historical data and statistical information, as well as a rule-based approach with a cost-based optimizer for generating a database execution plan and determining the most effective way of executing a SQL statement.
A database execution plan is essentially a virtual blueprint for the SQL statement detailing the steps needed for the RDBMS to access and retrieve data from its underlying tables and views. The database execution plan, which is fully transparent to the user, includes the list of operations and the order in which those operations will be executed. The plan also defines the specific algorithms and techniques to be used to retrieve the data requested in the statement.
In addition to creating the database execution plan, the query optimizer can also use its rules-based approach to determine if there is a more efficient query plan than the one generated. It can also look for any discrepancies, such as incorrect or missing indexes, or any potential areas in the query that can be improved upon.
An execution plan in SQL is important because it can help reduce the amount of time a user spends waiting for data to be retrieved from the database. It can also help reduce the memory, CPU, and input/output requirements for retrieving the data, leading to greater efficiency and faster query response times.
