The explain plan gives information on how the optimizer is going to execute the query. You just need to prefix the EXPLAIN keyword to the query:
mysql> EXPLAIN SELECT dept_name FROM dept_emp JOIN employees ON dept_emp.emp_no=employees.emp_no JOIN departments ON departments.dept_no=dept_emp.dept_no WHERE employees.first_name='Aamer'\G*************************** 1. row *************************** id: 1 select_type: SIMPLE table: employees partitions: NULL type: refpossible_keys: PRIMARY,name key: name key_len: 58 ref: const rows: 228 filtered: 100.00 Extra: Using index*************************** 2. row *************************** id: 1 select_type: SIMPLE table: dept_emp partitions: NULL type: refpossible_keys: PRIMARY,dept_no ...
