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)

LEFT JOIN

This type of JOIN is used when you want to select records that are available in the first table and match records in the second one. It can be represented with the following Venn diagram:

Figure 6.7: LEFT JOIN

The LEFT JOIN represents the highlighted section from TABLE A and the intersected section from TABLE B. Let's look at the syntax:

SELECT [Column List]
  FROM [Table 1] LEFT OUTER JOIN [Table 2] 
    ON [Table 1 Column Name] = [Table 2 Column Name]
WHERE [Condition]

The syntax can also be as follows:

SELECT [Column List]
  FROM [Table 1] LEFT JOIN [Table 2] 
    ON [Table 1 Column Name] = [Table 2 Column Name]
WHERE [Condition]

Note

The OUTER word in the query is optional.

This type of join is very similar to the RIGHT JOIN, with the only difference being that it executes the table on the opposite (left) side. Now that we have seen how we can implement LEFT JOIN...