In the previous sections, you used mysql interactively to enter queries and view the results. You can also run mysql in batch mode. To do this, put the commands you want to run in a file, then tell mysql to read its input from the file:
Wednesday, January 13, 2010
MySQL: Getting Information About Databases and Tables
What if you forget the name of a database or table, or what the structure of a given table is (for example, what its columns are called)? MySQL addresses this problem through several statements that provide information about the databases and tables it supports.
You have previously seen
You have previously seen
SHOW DATABASES, which lists the databases managed by the server. To find out which database is currently selected, use the DATABASE() function: MySQL: Retrieving Information from a Table
The
SELECT statement is used to pull information from a table. The general form of the statement is: SELECTwhat_to_selectFROMwhich_tableWHEREconditions_to_satisfy;
what_to_select indicates what you want to see. This can be a list of columns, or * to indicate “all columns.” which_table indicates the table from which you want to retrieve data. The WHERE clause is optional. If it is present, conditions_to_satisfy specifies one or more conditions that rows must satisfy to qualify for retrieval. MySQL: Loading Data into a Table
MySQL: Creating a Table
Creating the database is the easy part, but at this point it is empty, as
You want a table that contains a record for each of your pets. This can be called the
SHOW TABLES tells you: mysql> SHOW TABLES;
Empty set (0.00 sec)
The harder part is deciding what the structure of your database should be: what tables you need and what columns should be in each of them. You want a table that contains a record for each of your pets. This can be called the
pet table, and it should contain, as a bare minimum, each animal's name. Because the name by itself is not very interesting, the table should contain other information. For example, if more than one person in your family keeps pets, you might want to list each animal's owner. You might also want to record some basic descriptive information such as species and sex. MySQL: Creating and Selecting a Database
If the administrator creates your database for you when setting up your permissions, you can begin using it. Otherwise, you need to create it yourself:
mysql> CREATE DATABASE menagerie;
MySQL: Access a database
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 perform the following operations:
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 perform the following operations:
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