How to measure performance of query in oracle

Question

I\'m new to Oracle db. I have 2 queries which return the same result set. I want to measure the performance of each of them and choose the better one. How do I do that using Ora

Answer 1

Basic answer - execute each query a couple of times and see which one is faster. Best part - you can do this without learning about Oracle performance. The only thing you need to know is that you can not trust the first try because most of the time it will read data from disk while second try will use cached data from RAM. That is why you try each query a couple of times.