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.

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Table of Contents (13 chapters)
Preface
Preface
About the Book
About the Chapters
Free Chapter
1
1. SQL Basics
1. SQL Basics
Introduction
Understanding Data
An Overview of Basic SQL Commands
Data Types in SQL
Creating Simple Tables
Populating Your Tables
Summary
2
2. Manipulating Data
2. Manipulating Data
Introduction
The INSERT Operation
The DELETE Operation
The ALTER Operation
The UPDATE Operation
Summary
3
3. Normalization
3. Normalization
Introduction
Primary Key Constraints
Foreign Key Constraints
Preserving Data Integrity
Types of Data Integrity
The Concept of Normalization
First Normal Form (1NF)
Second Normal Form (2NF)
Third Normal Form (3NF)
Denormalization
Summary
4
4. The SELECT Statement
4. The SELECT Statement
Introduction
Retrieving All Columns of a Table
Summary
5
5. Shaping Data with the WHERE Clause
5. Shaping Data with the WHERE Clause
Introduction
The WHERE Clause Syntax
The Not Equal Operator
Checking for NULLS
Combining Conditions with the AND, OR, and NOT Operators
Summary
6
6. JOINS
6. JOINS
Introduction
INNER JOIN
RIGHT JOIN
LEFT JOIN
CROSS JOIN
UNION JOIN
Summary
7
7. Subqueries, Cases, and Views
7. Subqueries, Cases, and Views
Introduction
Subqueries
Case Statements
Views
Summary
8
8. SQL Programming
8. SQL Programming
Introduction
Programming for SQL Products – The Basics
Functions
Summary
9
9. Security
9. Security
Introduction
Access Control (Authorization)
Summary
10
10. Aggregate Functions
10. Aggregate Functions
Introduction
Aggregate Functions (SUM, COUNT, AVG, MIN, and MAX) and the GROUP BY Clause
The HAVING Clause
Summary
11
11. Advanced SQL
11. Advanced SQL
Introduction
String Functions
Transactions
Summary
Appendix
Appendix
1. SQL Basics
2. Manipulating Data
3. Normalization
4. The SELECT Statement
5. Shaping Data with the WHERE Clause
6. JOINS
7. Subqueries, Cases, and Views
8. SQL Programming
9. Security
10. Aggregate Functions
11. Advanced SQL
What Next?

Subqueries

In a SQL statement, a subquery operates like a joined table. It gathers data in a structured way and makes that data available for its outer SQL query. Placed in parentheses, a subquery, or an inner query, nests inside a parent, or an outer query. A subquery can nest in the following clauses of the parent query or another subquery:

  • SELECT
  • FROM
  • WHERE

A lot of the power of SQL products comes from their ability to link different tables in a single query. As we have seen already, we can link tables with inner and outer joins. In a query, we can also use a subquery to relate data from different tables. We can easily use the result of a subquery in the parent query without dealing with a join. Although queries with joins often have better performance, a subquery structure can seem a little more intuitive at first glance. Additionally, it's always good to have another option available when we build our queries. Both MySQL and SQL Server handle subqueries...

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