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The Language of SQL- P4

The Language of SQL- P4:Research has shown that, being pressed for time, most readers tend to skip the introduction of any book they happen to read and then proceed immediately to the first real chapter. With that fact firmly in mind, we will only cover relatively unimportant material in the introduction, such as an explanation of what you will and will not learn by reading this book. | CHAPTER 1 Relational Databases and SQL In this first chapter I m going to provide a bit of background that will allow you to get started quickly with the writing of SQL statements in subsequent chapters. There are two general topics. The first will be an overview of the databases covered in this book and some basic information on how those databases relate to the language of SQL. I ll also talk about the features of this book which will allow you to determine readily the SQL syntax for the specific database you re using. Second I m going to cover some of the key design features of relational databases. We ll talk about tables rows columns keys and datatypes. After you have the basic information you ll be up and running in no time. So without further ado let us begin. Language and Logic I must begin with an admission that the title of this book is not entirely appropriate. Although the book is entitled The Language of SQL a more apt title might have been The Logic of SQL. This is because like all computer languages the language of SQL has much more to do with cold hard logic than with English vocabulary. Nevertheless there is a unique language-based syntax present in SQL that distinguishes it from many other computer languages. Unlike many programming tools SQL employs ordinary English words such as WHERE FROM and HAVING 1 2 Chapter 1 Relational Databases and SQL as keywords in its syntax. As a result SQL is much less cryptic than other languages you might have seen. As such after you become familiar with the language of SQL you might find yourself thinking of SQL commands as being analogous to English sentences and having a certain expressive meaning. For example compare this sentence I would like a hamburger and fries from your value menu and make it to go. with this SQL statement Select city state from customers order by state I ll get into the details later but this SQL statement means that you want the city and state fields from a customer s table in your .