When we say “window,” we mean a particular part of your database on which we want to apply some function. The functions to use can be ranking window functions (ROW_NUMBER(), RANK(), or DENSE_RANK()), value window functions (LAG() and LEAD()), or MySQL aggregate window functions applied in the context of window functions, such as MAX() or MIN().

This section covers MySQL Common Table Expressions (CTEs)—a tool allowing you to obtain a temporary result set that you can use and reuse within the scope of a query. More precisely, we’ll explore single and multiple subclauses in a WITH clause and refer to already specified common table expressions in a WITH clause.

As you progress as an SQL analyst, you’ll increasingly work with more extensive databases containing tables with millions of records. In other words, the queries you write can easily take a few minutes before returning the desired result. In such cases, you’ll look for tools like MySQL temporary tables to increase the efficiency of the data retrieval process. In this section, you’ll create your first MySQL Temporary Table and explore some of its features.