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)

The UPDATE Operation

As we saw in the overview, UPDATE modifies data in one or more columns in a table. Just like the INSERT operation, the UPDATE operation can also only be performed against a single table using a single statement. In most situations, you will filter out the records you would like to update and update only them. This filtration is done using a WHERE clause in the SELECT statement. The UPDATE statement also contains a SET clause, which defines what needs to be modified within the table, along with the values.

In our demo, we'll update a table called email. You can set one column or more during an UPDATE operation. If you want to update multiple columns, separate the column names with a comma.

The database engine looks for the column that is specified in the statement and updates all the rows in it. If you would like to update only a certain row or a certain set of rows, you would use the WHERE clause. This way, you can identify only those intersections of...