If you are running SQL*Plus, you can turn on timing (SET TIMING ON) to get a rough idea. If you require more accurate measurement, enable SQL trace and inspect the resulting trace file after processing it with TKPROF. As to how to improve execution time, that's far too general a question; every query and every database are different.
Dig deeper on Oracle database performance problems and tuning
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.