how to write an optimized query

with a keyboard, i guess

Read about Functional indexes. These are great for resolving tuning issues. I think it was introduced in 8i database version. Ashutosh

When you say you want to write optimized query that means that you are looking for perfect query which executes in less time. By default oracle has CBO cost based optimization. Still you can use hits to write optimized SQL. There are some plsql resource provided in the following link. http://easyapps.blogspot.com Its good that you are learning Oracle, its future for any techie.

Also get a book on tuning from oracle press. ash

Read about explain plan. Cost and rule based optimizers Indexes Internet is your best resource to learn Tuning. Regards Ashutosh Parekh (Oracle DBA)