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

I'm afraid EXPLAIN PLAN is the only way. Start off by assuming that a lower cost (if you look at the explain plan there should be a column called COST) is better, but you need to read up about it so that you learn more and more. Maybe you have a DBA there that you could chat stuff through with? Without having your data and the queries it is difficult to advise further

For anything to do with developing Oracle, a good place to start is anything by Tom Kyte (Google him) or search through the Ask Tom website. If you really want to get involved

Only running the query a few times is a pretty bad idea - equivalent to just accepting that the cost of the explain plan tells you the best query. You really need to take into account what resources your query is taking up and therefore how it could affect you production system.

Depending on how often the query gets called affects how well you need to track a query's performance (sorry to purists, but it does). If the query only runs once a week and takes a minute to run without affecting anything else then do you need to optimise that query? Is it easier for maintenance to use a query that is more easy to logically follow?

If the query is being called multiple times a second then you need to completely understand the explain plan, and have a further understanding on how you can optimise the query to its best performance