Book Image

The MySQL Workshop

By : Thomas Pettit, Scott Cosentino
5 (1)
Book Image

The MySQL Workshop

5 (1)
By: Thomas Pettit, Scott Cosentino

Overview of this book

Do you want to learn how to create and maintain databases effectively? Are you looking for simple answers to basic MySQL questions as well as straightforward examples that you can use at work? If so, this workshop is the right choice for you. Designed to build your confidence through hands-on practice, this book uses a simple approach that focuses on the practical, so you can get straight down to business without having to wade through pages and pages of dull, dry theory. As you work through bite-sized exercises and activities, you'll learn how to use different MySQL tools to create a database and manage the data within it. You'll see how to transfer data between a MySQL database and other sources, and use real-world datasets to gain valuable experience of manipulating and gaining insights from data. As you progress, you'll discover how to protect your database by managing user permissions and performing logical backups and restores. If you've already tried to teach yourself SQL, but haven't been able to make the leap from understanding simple queries to working on live projects with a real database management system, The MySQL Workshop will get you on the right track. By the end of this MySQL book, you'll have the knowledge, skills, and confidence to advance your career and tackle your own ambitious projects with MySQL.
Table of Contents (22 chapters)
1
Section 1: Creating Your Database
6
Section 2: Managing Your Database
11
Section 3: Querying Your Database
16
Section 4: Protecting Your Database

Analyzing query performance with EXPLAIN

EXPLAIN is a very useful tool when it comes to performance. The SQL query is used to tell the database what you want, but EXPLAIN asks the database how it thinks it is going to do it.

Let's use the city table in the world_simple database as an example:

SELECT * FROM city WHERE ID=2460;
EXPLAIN SELECT * FROM city WHERE ID=2460;

This produces the following output:

Figure 5.30 – SELECT and EXPLAIN

Note that it says 1 warning. You can see the actual message by running SHOW WARNINGS;. This is expected for EXPLAIN as there will be a note with a rewritten version of the statement. You can ignore this for now.

We select a single city (Skopje) and are using an ID (2460) to do this lookup.

Let's go over the EXPLAIN output to see what each field means:

Figure 5.31 – Meaning of each field

Now let's add a primary key to this table and run EXPLAIN...