Have you ever researched and evaluated SQL query execution plans in a database?

Yes, analyzing and evaluating SQL query execution plans is an important step in optimizing database performance. I usually use the EXPLAIN or EXPLAIN ANALYZE commands (depending on the DBMS) to obtain the execution plan of a query. This allows us to see which indexes are used, the join order of tables, operation types (such as sequential scan, index search), and estimated costs.

For example, in PostgreSQL, you can run:

EXPLAIN ANALYZE SELECT * FROM orders WHERE customer_id = 123;

By analyzing the output, you can determine whether to create additional indexes or rewrite the query for better efficiency.