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3.3 Creating and Using a Database
=================================
Menu
* creating-database Creating and Selecting a Database
* creating-tables Creating a Table
* loading-tables Loading Data into a Table
* retrieving-data Retrieving Information from a Table
Once you know how to enter commands, you are ready to access a database.
Suppose that you have several pets in your home (your menagerie) and
you would like to keep track of various types of information about
them. You can do so by creating tables to hold your data and loading
them with the desired information. Then you can answer different sorts
of questions about your animals by retrieving data from the tables.
This section shows you how to:
* Create a database
* Create a table
* Load data into the table
* Retrieve data from the table in various ways
* Use multiple tables
The menagerie database is simple (deliberately), but it is not
difficult to think of real-world situations in which a similar type of
database might be used. For example, a database like this could be used
by a farmer to keep track of livestock, or by a veterinarian to keep
track of patient records. A menagerie distribution containing some of
the queries and sample data used in the following sections can be
obtained from the MySQL Web site. It is available in both compressed
`tar'
(`http://www.mysql.com/Downloads/Contrib/Examples/menagerie.tar.gz')
and Zip
(`http://www.mysql.com/Downloads/Contrib/Examples/menagerie.zip')
formats.
Use the `SHOW' statement to find out what databases currently exist on
the server:
mysql> SHOW DATABASES;
+----------+
| Database |
+----------+
| mysql |
| test |
| tmp |
+----------+
The list of databases is probably different on your machine, but the
`mysql' and `test' databases are likely to be among them. The `mysql'
database is required because it describes user access privileges. The
`test' database is often provided as a workspace for users to try
things out.
Note that you may not see all databases if you do not have the `SHOW
DATABASES' privilege. See grant.
If the `test' database exists, try to access it:
mysql> USE test
Database changed
Note that `USE', like `QUIT', does not require a semicolon. (You can
terminate such statements with a semicolon if you like; it does no
harm.) The `USE' statement is special in another way, too: it must be
given on a single line.
You can use the `test' database (if you have access to it) for the
examples that follow, but anything you create in that database can be
removed by anyone else with access to it. For this reason, you should
probably ask your MySQL administrator for permission to use a database
of your own. Suppose that you want to call yours `menagerie'. The
administrator needs to execute a command like this:
mysql> GRANT ALL ON menagerie.* TO 'your_mysql_name'@'your_client_host';
where `your_mysql_name' is the MySQL user name assigned to you and
`your_client_host' is the host from which you connect to the server.
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