Book Image

Learn SQL Database Programming

By : Josephine Bush
5 (1)
Book Image

Learn SQL Database Programming

5 (1)
By: Josephine Bush

Overview of this book

SQL is a powerful querying language that's used to store, manipulate, and retrieve data, and it is one of the most popular languages used by developers to query and analyze data efficiently. If you're looking for a comprehensive introduction to SQL, Learn SQL Database Programming will help you to get up to speed with using SQL to streamline your work in no time. Starting with an overview of relational database management systems, this book will show you how to set up and use MySQL Workbench and design a database using practical examples. You'll also discover how to query and manipulate data with SQL programming using MySQL Workbench. As you advance, you’ll create a database, query single and multiple tables, and modify data using SQL querying. This SQL book covers advanced SQL techniques, including aggregate functions, flow control statements, error handling, and subqueries, and helps you process your data to present your findings. Finally, you’ll implement best practices for writing SQL and designing indexes and tables. By the end of this SQL programming book, you’ll have gained the confidence to use SQL queries to retrieve and manipulate data.
Table of Contents (24 chapters)
Section 1: Database Fundamentals
Section 2: Basic SQL Querying
Section 3: Advanced SQL Querying
Section 4: Presenting Your Findings
Section 5: SQL Best Practices

Understanding aggregate functions

Aggregate functions include numeric and statistical built-in functions. These topics were covered in more detail in Chapter 9, Working with Expressions. The following is a recap from that chapter.

Numeric aggregate functions

Numeric built-in functions handle mathematical calculations. They can all operate on a numeric data type table column or an expression of a numeric data type. The following list shows a sample of these functions:

  • AVG: Returns the average of an expression:
  • AVG(rating): This will return the average of all the values in a rating column.
  • NULL values are ignored.
  • COUNT: Returns the number of records:
  • COUNT(column1): This will return the count of values in column1 : column1...