Book Image

The SQL Workshop

By : Frank Solomon, Prashanth Jayaram, Awni Al Saqqa
Book Image

The SQL Workshop

By: Frank Solomon, Prashanth Jayaram, Awni Al Saqqa

Overview of this book

Many software applications are backed by powerful relational database systems, meaning that the skills to be able to maintain a SQL database and reliably retrieve data are in high demand. With its simple syntax and effective data manipulation capabilities, SQL enables you to manage relational databases with ease. The SQL Workshop will help you progress from basic to advanced-level SQL queries in order to create and manage databases successfully. This Workshop begins with an introduction to basic CRUD commands and gives you an overview of the different data types in SQL. You'll use commands for narrowing down the search results within a database and learn about data retrieval from single and multiple tables in a single query. As you advance, you'll use aggregate functions to perform calculations on a set of values, and implement process automation using stored procedures, functions, and triggers. Finally, you'll secure your database against potential threats and use access control to keep your data safe. Throughout this Workshop, you'll use your skills on a realistic database for an online shop, preparing you for solving data problems in the real world. By the end of this book, you'll have built the knowledge, skills and confidence to creatively solve real-world data problems with SQL.
Table of Contents (13 chapters)

Transactions

As part of database management, soon enough, we will probably make direct data changes through database management tools. In other words, we may use a MySQL query window to make a direct insert, update, and delete changes to live production data. We know how to make those changes with relevant SQL statements, but so far, we have not looked at a way to reverse these changes. Even one mistake could potentially destroy data resources worth billions. Fortunately, SQL products offer the TRANSACTION function as a way to execute SQL statements in a reversible way.

From the PACKT_ONLINE_SHOP database, from the Products table, let's query the product with the product ID 3:

USE PACKT_ONLINE_SHOP;
SELECT    ProductID, Availablequantity
FROM      Products
WHERE     productid = 3;

This query will yield the following output:

Figure 11.16: The output of the query before update

From the output, we can see that the product with product ID 3 has 1...