Databases Reference
In-Depth Information
SHOW DATABASES lists the databases on the MySQL server host. You see
only those databases for which you have some kind of privilege, unless
you have the global SHOW DATABASES privilege. You can also get this
list using the mysqlshow command.
If the server was started with the --skip-show-database option, you
cannot use this statement at all unless you have the SHOW DATABASES
privilege.
SHOW SCHEMAS can be used as of MySQL 5.0.2
Running the Monitor in Batch Mode
The MySQL monitor can be used in
interactive mode
or in
batch mode
. In interactive
mode, you type in SQL queries or MySQL commands such as
SHOW DATABASES
at the
MySQL prompt, and view the results.
In batch mode, you tell the monitor to read in and execute a list of commands from a
file. This is useful when you need to run a large set of operations—for example, when
you want to restore a database from a backup file. It's also useful when you need to
run a particular sequence of operations frequently; you can save the commands in a
file and then tell the monitor to read in the file whenever you need it.
The examples we've presented earlier in this chapter, and most of the examples in this
book, show the monitor being used in interactive mode. Let's look at an example for
batch mode. Say you have a text file called
count_users.sql
containing the SQL
commands:
use mysql;
SELECT COUNT(*) FROM user;
This script tells MySQL that you want to use the
mysql
database, and that you want to
count all the users who have accounts on the MySQL server (we'll explain the syntax
of the
SELECT
command in Chapter 5).
You can run all the commands in this file using the
SOURCE
command:
mysql>
SOURCE count_users.sql
Database changed
+----------+
| count(*) |
+----------+
| 4 |
+----------+
1 row in set (0.00 sec)
If the
count_users.sql
file isn't in the current directory, you should give the full path to
the file—for example,
/home/adam/Desktop/count_users.sql
or
C:\count_users.sql
. Al-
ternatively, from the command line, you can use the less-than (<) redirection operator
followed by the filename:
