Execution plan (SQL)

Execution plan (SQL) is a technical description of how an SQL statement will be executed, generated and optimized by the database optimizer of the database management system. The plan gives a detailed step-by-step description of how the query will be executed, including which indexes will be used, what the join order is, and whether sorting or aggregation is needed.

The execution plan includes a graphical (in some implementations) as well as a text representation, which is helpful in debugging and troubleshooting SQL statements that don’t return the expected results. The graphical plan allows SQL developers and DBAs to easily see which and how different index/table nodes are joined together.

The execution plan of a query is very important in optimizing the performance of the query. It will give insight which portions of a query are performing better and which are more time consuming. This will help the developers in restructuring the code of the query and optimizing it.

When it comes to performance tuning, examining the execution plan will provide insight into the most expensive part of the query so that part can be broken down into multiple simpler queries and providing an overall improvement in the performance. It will also help to detect any missing indexes or potential JOIN issues in the query.

In a nutshell, understanding and optimizing execution plans of SQL statements is critical to ensure database performance. It helps make informed decisions as to how to optimize the query for better performance.