How can the efficiency of executing an SQL query be evaluated?

The following methods are usually used to evaluate the effectiveness of executing an SQL query:

• EXPLAIN / EXPLAIN ANALYZE: Provides an execution plan of the query, showing which indexes are used, the order of operations, the number of rows processed, and an approximate time.

• Profiling execution time: Measuring the query execution time using built-in DBMS tools or external tools.

• Resource usage analysis: Checking CPU, memory, and disk load during query execution.

• Index optimization: Checking whether indexes are used and creating new ones if necessary.

Example of using EXPLAIN in PostgreSQL:

EXPLAIN ANALYZE SELECT * FROM users WHERE age > 30;

This will provide a detailed report on how the DBMS executes the query and where performance can be improved.