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 HAVING Clause

As we saw, the aggregate functions will solve many problems for us. Eventually, however, we'll want to filter the aggregate function value of a query result set. We have learned how to build SQL queries that calculate aggregate function values. If we want to filter the query results on those aggregate function values, the WHERE clause won't work. For example, we might want to see the query results of a SQL MAX function that land below a specific value. We might need the query results of a SQL AVG function that match a specific value. The HAVING clause will help. Starting with this query, suppose we want only those rows with MINIMUM NET RETAIL PRICE values greater than 5.00 in the result set:

USE        packt_online_shop;
SELECT     PC.ProductCategoryID, PC.ProductCategoryName,           AVG(P.UnitKGWeight) AS 'AVERAGE PRODUCT KG WEIGHT',           MIN(P.NetRetailPrice) AS 'MINIMUM NET RETAIL PRICE'
FROM       ProductCategories PC INNER...