Packed with examples, Simply SQL is a step-by-step introduction to learning SQL. This book focuses on the practical use of SQL with common databases and uses  plenty of diagrams, easy-to-read text, and examples to help make learning SQL easy and fun.

Simply SQL

Preface

Almost every web site nowadays, it seems, uses a database. Your objective, as a web developer, is to be able to design or build web sites that use a database. To do this, you must acquire an understanding of and the ability to use Structured Query Language (SQL), the language used to communicate with databases.

An Introduction to SQL

In Chapter 1, our quick introduction to SQL, we briefly met the main SQL statements that we will encounter as web developers:

An Overview of the SELECT Statement

In Chapter 2, we broke the SELECT tatement down into its various clauses, but looked at each clause only briefly. In this chapter, we’ll begin our more detailed look at the SELECT statement, starting with the FROM clause.

The FROM Clause

The WHERE clause is the second clause of the SQL SELECT statement that we’ll now discuss in detail. The FROM clause, which we covered in the previous chapter, introduced the central concept behind SQL: tabular structures . It is the first clause that the database system parses and executes when we run an SQL query. A tabular structure is produced by the FROM clause using tables, joins, views, or subqueries. This tabular structure is referred to as the result set of the FROM clause.

The WHERE Clause

In Chapter 3, we learned that the FROM clause creates the intermediate tabular result containing the data for a query. In Chapter 4, we learned that the WHERE clause acts as a filter on the rows produced by the FROM clause. In this chapter, we'll learn what happens when we use the GROUP BY clause, and the effect it has on the data produced by the FROM clause and filtered by the WHERE clause.

The GROUP BY Clause

In Chapter 5, we learned that the GROUP BY clause produces group rows by aggregating rows of the tabular structure extracted from the database by the FROM clause and then filtered by the WHERE clause. Each distinct value or combination of values in the GROUP BY column(s) forms a separate group row.

The HAVING Clause

The SELECT clause has been used in every sample SQL SELECT statement we’ve seen so far. This is not surprising, because the SELECT clause is mandatory; it’s the first clause in any SELECT statement. I’ve tried to avoid describing the SELECT clause in too much detail along the way, in order not to detract from the other clauses being discussed, but now it’s time for us to get to know the SELECT clause a little better.

The SELECT Clause

In this chapter, we’ll look at the ORDER BY clause, the last of the clauses of the SELECT SQL statement. [6] Not only is ORDER BY the last clause in the syntax, it’s also the last clause in the execution sequence. Fortunately, ORDER BY is a really simple clause, so let’s jump right in.

The ORDER BY Clause

Not everything that counts can be counted, and not everything that can be counted counts. --Albert Einstein 

SQL Data Types

What's in a name? that which we call a rose By any other name would smell as sweet; --Juliet 

Relational Integrity

Classifications are theories about the basis of natural order, not dull catalogs compiled only to avoid chaos. --Stephen Jay Gould 

Community Questions