If I had a penny for every time someone asked me to show them an easy way to learn tuning...

select 8 from emp;

Quote:

If I had a penny for every time someone asked me to show them an easy way to learn tuning...

There is no easy path to understanding tuning. Consider this: many of us on OraFAQ have been Oracle Database users for 10 years, 20 years, and even 30 years. That's a long time. I personally typed

select 8 from emp;

into a SQL prompt back in 1985 (yep that says 8 not * (I fat fingered my very first SQL statement)). For those of us who have spent these many years working with the Oracle database, we have learned a lot about tuning, yet we might still hesitate to call ourselves Experts at it. There is no short path and it is hard work to get good at it and just as hard to stay good at it given things change so fast.

One of the biggest reasons that tuning is so hard to learn is that there is a CRITICAL MASS OF KNOWLEDGE that must first be attained before one starts to really understand tuning, and there is a wealth of crap out there that anyone interested in acquiring this critical mass of knowledge, must wade through in order to get the gold we seek. Having spent my career reading and learning I understand your frustrations about learning how to tune as I have read most of this crap. Learning to tune takes a lot of time whether you learn vicariously or through direct experience.

For this reason I think it is the duty of those of us who have the experience, to help newcomers focus on the important aspects of tuning so that the best parts of our many years of experience can be digested with in a time frame of an order of magnitude less maybe. Of course this still means best case, two to three years for you to get reasonably good at practical tuning and that is with experienced mentors helping you skip the crap and showing you where the good stuff is, so that you are not wasting your time like we had to do. Use this comment to grasp what is ahead of you if you want to be a good query tuner.

You did mention in your post the term "QUERY TUNING" so I will start you off with a simple question, and a pointer to one of my best posts on OraFAQ (I think anyway). Others can follow suit with their best starting tips if they feel so inclined.

Q: If you have a table with 1 million rows and you want all 1 million rows from it, should you use an index to get all these rows or do a full table scan? Why?

Understanding the WHY of this question will give you an appreciation for the very heart of query tuning.

Sadly, this link no longer points to the proper place. Please ignore it. Not sure how that happened. Kevin 22-Jan-2014.
Query tuning actually starts way before writing any SQL. This link shows you the most important thing you can do for query performance.

Good luck. Kevin