A Practical Introduction
By Akeel I Din
Introduction
The Structured Query Language, SQL is a query language which is used with relational databases. This chapter starts by describing some of the terms used in data processing and how they relate to SQL. The later part of this chapter describes relational databases and how SQL is used to query them.
Let's start from basics. What is a database? In very general terms, a database is a collection of related data. Notice the word related, this implies that the collection of letters on this page do not by themselves constitute a database. But if we think of them as a collection of letters arranged to form words, then they can be conceptualised as data in a database. Using similar reasoning, we can also say that a tome such as a telephone directory is also a database. It is a database first, because it is a collection of letters that form words and second, because it is an alphabetical listing of people's names, their addresses and their telephone numbers. How we think of a database depends on what use we want to make of the information that it contains.
The Structured Query Language, SQL is a query language which is used with relational databases. This chapter starts by describing some of the terms used in data processing and how they relate to SQL. The later part of this chapter describes relational databases and how SQL is used to query them.
"A Collection of Related Data": Databases and Database Management Systems.
Let's start from basics. What is a database? In very general terms, a database is a collection of related data. Notice the word related, this implies that the collection of letters on this page do not by themselves constitute a database. But if we think of them as a collection of letters arranged to form words, then they can be conceptualised as data in a database. Using similar reasoning, we can also say that a tome such as a telephone directory is also a database. It is a database first, because it is a collection of letters that form words and second, because it is an alphabetical listing of people's names, their addresses and their telephone numbers. How we think of a database depends on what use we want to make of the information that it contains.