How to Write Optimal SQL Queries

Question

I\'ve searched around stackoverflow but everybody asks to optimize queries they\'ve already done.

I want to know, the basic stuff on what to do, what to avoid when creat

Answer 1

A few general points about optimizing queries:

• Know your data. Know your data. Know your data. I would venture to guess that half of all database performance problems stem from an incomplete understanding of the data and the requirements of the query. Know if your query will be usually returning 50 rows or 5 million rows. Know if you need to get back 3 columns or 50 columns. Know what columns are key columns on the tables, and filter on these.

• Understand your database structure. If you're working with a database in third-normal form, recognize that this structure typically works best on queries for lots of small, transactional statements operating on individual rows. If you are working in a star or snowflake design, recognize that it's optimized for large queries and aggregations.