Critical Skill 1.1 Know Basic Database Terms

Every area of study either evolves its own language or adopts familiar words to be used in a new context. Computer jargon is no exception, and the subject of databases has its usual share of seemingly ordinary words, which suddenly take on new meaning when you venture into this new realm.

Fortunately, the terms used to talk about databases are everyday words and easy to remember. The real confusion comes from the fact that, in a several cases, more than one word is used to refer to the same thing. However, there are occasionally subtle distinctions. For example, the terms column and row are usually used when referring to the dimensions of the database, and the terms field and record are usually used when referring to the contents of the database. But for all practical purposes, the words column and field mean the same thing, as do row and record , and the terms are used interchangeably. As long as you remember that the terms are basically interchangeable, you will get the gist of it.

Table 1-1 defines some common terms used with databases.

Table 1-1: Common Terms Used with Databases

Field	A single piece of information defined by type, length, and other attributes
Record	A single set of fields, which are ordered in a defined manner and related as a single set of information
Column	Used interchangeably with field , it also implies every instance of that field in every row of the database table
Row	Used interchangeably with record
Table	A finite set of defined, ordered columns (fields), which can contain any number of rows (records)
Relational database	A database in which data items and the relationships between them are gathered in a table or collection of tables, in which certain fields can be set as keys to aid data retrieval
Key	A field set as the specific piece of a record used for indexing the data for quicker retrieval
Index	Used interchangeably with key

There is one more thing about MySQL terminology that leads to some degree of confusion. The MySQL AB (the official name of the company that maintains and distributes MySQL) developers decided to name everything to do with their program MySQL. The database server, the database client, and the default database that holds the login and other operational information are all forms of MySQL .

When you install and start MySQL, you are starting the MySQL Server (or Service). This means that the software that is the active part of the program, together with its settings and databases, is running and accessible.

The next step usually involves communicating with the MySQL Service, and that is done via the MySQL Client. You open the MySQL Client by running a command on your computer s command line. You have probably guessed by now that the command to do that is also mysql . At this point, your normal command-line prompt is replaced by the MySQL Client prompt, which unsurprisingly, looks like this:

 mysql> 

When you run the command to show the default tables installed in MySQL, you see two tables listed: test and, once again, mysql .

In order to be clear in this book, when we refer to MySQL, we mean the entire program or the company that makes it. We will refer to the other three components as the MySQL Server, the MySQL Client, and the mysql database.