Can you explain what a query execution plan in a relational database is?

The SQL query execution plan is a detailed set of steps that the database uses to obtain the query result. It shows exactly how the DBMS will execute the query: which tables and indexes to use, in what order to join data, what filtering and sorting operations to apply.

The plan helps understand the query's efficiency and identify bottlenecks. It can usually be obtained using the EXPLAIN command or similar tools in a specific DBMS.

An example of a plan may include:

• Table or index scan
• Table joins (JOIN)
• Row filtering (WHERE)
• Sorting (ORDER BY)

This is important for query optimization and improving database performance.