SQL is easy to start writing. The basic syntax to start returning data is very simple. This low threshold for starting SQL hides some of the nuances that divide efficient queries from inefficient queries. As your SQL gets more complicated and you need to join multiple tables and perform intricate operations on the data, it is important to understand the basics of how queries are processed and how your query decisions impact performance.
The ability to write an efficient query starts with a well-designed database. If the database you are working with is poorly designed, your choices are limited. Even