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 subqueries

Another way of joining the tables is available in MySQL. It consists of using the output of a query directly in another query.

Use the world_simple table as an example again and look at the following query:

SELECT Name FROM city WHERE CountryCode=(
  SELECT Code FROM country WHERE Name='Romania'
);

This query produces the following output:

Figure 5.17 – SELECT with a subquery

The preceding query is essentially running this command:

SELECT Code FROM country WHERE Name='Romania';

It then saves the result and runs the following query:

SELECT Name FROM city WHERE CountryCode=<saved_result>

So, to use a subquery, you place the query inside ( and ) and place it where you want to see the output. This can be in the WHERE part of the query, but also the SELECT part and most other places.

Dependent subqueries

In the previous example, the two queries were independent, but in some...