Set - 4

Question 6 :

Entity-relationship modeling

Answer :

A technique used to describe the real-world data in terms of entities, attributes, and relationships.


Question 7 :

Normalized database

Answer :

A correctly designed database that is created from an ER model. There are different types or levels of normalization, and a third-normal form database is generally regarded as being an acceptably designed relational database.


Question 8 :

MySQL Command Interpreter

Answer :

The MySQL command interpreter is commonly used to create databases and tables in web database applications and to test queries. Throughout the remainder of this chapter we discuss the SQL statements for managing a database. All these statements can be directly entered into the command interpreter and executed. The statements can also be included in server-side PHP scripts, as discussed in later chapters.

Once the MySQL DBMS server is running, the command interpreter can be used. The command interpreter can be run using the following command from the shell, assuming you've created a user hugh with a password shhh:

% /usr/local/bin/mysql -uhugh -pshhh The shell prompt is represented here as a percentage character, %.

Running the command interpreter displays the output:
Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 36 to server version: 3.22.38
Type 'help' for help.

mysql>
The command interpreter displays a mysql> prompt and, after executing any command or statement, it redisplays the prompt. For example, you might issue the statement:

mysql> SELECT NOW( );
This statement reports the time and date by producing the following output:

+---------------------+
| NOW( ) |
+---------------------+
| 2002-01-01 13:48:07 |
+---------------------+
1 row in set (0.00 sec)

mysql>
After running a statement, the interpreter redisplays the mysql> prompt. We discuss the SELECT statement later in this chapter.

As with all other SQL statements, the SELECT statement ends in a semicolon. Almost all SQL command interpreters permit any amount of whitespace—spaces, tabs, or carriage returns—in SQL statements, and they check syntax and execute statements only after encountering a semicolon that is followed by a press of the Enter key. We have used uppercase for the SQL statements throughout this book. However, any mix of upper- and lowercase is equivalent.

On startup, the command interpreter encourages the use of the help command. Typing help produces a list of commands that are native to the MySQL interpreter and that aren't part of SQL. All non-SQL commands can be entered without the terminating semicolon, but the semicolon can be included without causing an error.

The MySQL command interpreter allows flexible entry of commands and SQL statements:

The up and down arrow keys allow previously entered commands and statements to be browsed and used.

The interpreter has command completion. If you type the first few characters of a string that has previously been entered and press the Tab key, the interpreter automatically completes the command. For example, if wines is typed and the Tab key pressed, the command interpreter outputs winestore, assuming the word winestore has been previously used.

If there's more than one option that begins with the characters entered, or you wish the strings that match the characters to be displayed, press the Tab key twice to show all matches. You can then enter additional characters to remove any ambiguity and press the Tab key again for command completion.

Several common statements and commands are pre-stored, including most of the SQL keywords discussed in this chapter.

To use the default text editor to create SQL statements, enter the command edit in the interpreter. This invokes the editor defined by the EDITOR shell environment variable. When the editor is exited, the MySQL command interpreter reads, parses, and runs the file created in the editor.

When the interpreter is quit and run again later, the history of commands and statements is kept. It is still possible to scroll up using the up arrow and to execute commands and statements that were entered earlier.

You can run commands and SQL statements without actually launching the MySQL command interpreter. For example, to run SELECT now( ) from the Linux shell, enter the following command:

mysql -ppassword -e "SELECT now( );" This is particularly useful for adding SQL commands to shell or other scripts.


Question 9 :

Installing a MySQL Binary Distribution

Answer :

You need the following tools to install a MySQL binary distribution:
GNU gunzip to uncompress the distribution.
A reasonable tar to unpack the distribution. GNU tar is known to work. Sun tar is known to have problems.
An alternative installation method under Linux is to use RPM (RedHat Package Manager) distributions.

If you run into problems, PLEASE ALWAYS USE mysqlbug when posting questions to mysql@lists.mysql.com. Even if the problem isn't a bug, mysqlbug gathers system information that will help others solve your problem. By not using mysqlbug, you lessen the likelihood of getting a solution to your problem! You will find mysqlbug in the `bin' directory after you unpack the distribution.

The basic commands you must execute to install and use a MySQL binary distribution are:

shell> groupadd mysql
shell> useradd -g mysql mysql
shell> cd /usr/local
shell> gunzip < /path/to/mysql-VERSION-OS.tar.gz | tar xvf -
shell> ln -s mysql-VERSION-OS mysql
shell> cd mysql
shell> scripts/mysql_install_db
shell> chown -R mysql /usr/local/mysql
shell> chgrp -R mysql /usr/local/mysql
shell> bin/safe_mysqld --user=mysql &

You can add new users using the bin/mysql_setpermission script if you install the DBI and Msql-Mysql-modules Perl modules.
A more detailed description follows.

Pick the directory under which you want to unpack the distribution, and move into it. In the example below, we unpack the distribution under `/usr/local' and create a directory `/usr/local/mysql' into which MySQL is installed. (The following instructions therefore assume you have permission to create files in `/usr/local'. If that directory is protected, you will need to perform the installation as root.)

How to Get MySQL. MySQL binary distributions are provided as compressed tar archives and have names like `mysql-VERSION-OS.tar.gz', where VERSION is a number (for example, 3.21.15), and OS indicates the type of operating system for which the distribution is intended (for example, pc-linux-gnu-i586). Add a user and group for mysqld to run as:
shell> groupadd mysql
shell> useradd -g mysql mysql

These commands add the mysql group and the mysql user. The syntax for useradd and groupadd may differ slightly on different Unixes. They may also be called adduser and addgroup. You may wish to call the user and group something else instead of mysql.
Change into the intended installation directory:
shell> cd /usr/local>
Unpack the distribution and create the installation directory:
shell> gunzip < /path/to/mysql-VERSION-OS.tar.gz | tar xvf -
shell> ln -s mysql-VERSION-OS mysql

The first command creates a directory named `mysql-VERSION-OS'. The second command makes a symbolic link to that directory. This lets you refer more easily to the installation directory as `/usr/local/mysql'.
Change into the installation directory:
shell> cd mysql

You will find several files and subdirectories in the mysql directory. The most important for installation purposes are the `bin' and `scripts' subdirectories.
`bin'
This directory contains client programs and the server You should add the full pathname of this directory to your PATH environment variable so that your shell finds the MySQL programs properly.
`scripts'
This directory contains the mysql_install_db script used to initialize the server access permissions.
If you would like to use mysqlaccess and have the MySQL distribution in some nonstandard place, you must change the location where mysqlaccess expects to find the mysql client. Edit the `bin/mysqlaccess' script at approximately line 18. Search for a line that looks like this:
$MYSQL = '/usr/local/bin/mysql'; # path to mysql executable

Change the path to reflect the location where mysql actually is stored on your system. If you do not do this, you will get a Broken pipe error when you run mysqlaccess.
Create the MySQL grant tables (necessary only if you haven't installed MySQL before):
shell> scripts/mysql_install_db

Note that MySQL versions older than Version 3.22.10 started the MySQL server when you run mysql_install_db. This is no longer true! Change ownership of the installation directory to the user that you will run mysqld as:
shell> chown -R mysql /usr/local/mysql
shell> chgrp -R mysql /usr/local/mysql

The first command changes the owner attribute of the files to the mysql user, and the second changes the group attribute to the mysql group.
If you would like MySQL to start automatically when you boot your machine, you can copy support-files/mysql.server to the location where your system has its startup files. More information can be found in the support-files/mysql.server script itself.
After everything has been unpacked and installed, you should initialize and test your distribution.

You can start the MySQL server with the following command:

shell> bin/safe_mysqld --user=mysql &


Question 10 :

MySQL - Quick Installation Overview

Answer :

The basic commands you must execute to install a MySQL source distribution are:
shell> groupadd mysql
shell> useradd -g mysql mysql
shell> gunzip < mysql-VERSION.tar.gz | tar -xvf -
shell> cd mysql-VERSION
shell> ./configure --prefix=/usr/local/mysql
shell> make
shell> make install
shell> scripts/mysql_install_db
shell> chown -R mysql /usr/local/mysql
shell> chgrp -R mysql /usr/local/mysql
shell> /usr/local/mysql/bin/safe_mysqld --user=mysql &

If you start from a source RPM, then do the following:

shell> rpm --rebuild MySQL-VERSION.src.rpm

This will make a binary RPM that you can install.

You can add new users using the bin/mysql_setpermission script if you install the DBI and Msql-Mysql-modules Perl modules.
A more detailed description follows.

Pick the directory under which you want to unpack the distribution, and move into it.
If you are interested in using Berkeley DB tables with MySQL, you will need to obtain a patched version of the Berkeley DB source code. Please read the chapter on Berkeley DB tables before proceeding.
MySQL source distributions are provided as compressed tar archives and have names like `mysql-VERSION.tar.gz', where VERSION is a number like 3.23.33.
Add a user and group for mysqld to run as:
shell> groupadd mysql
shell> useradd -g mysql mysql

These commands add the mysql group, and the mysql user. The syntax for useradd and groupadd may differ slightly on different Unixes. They may also be called adduser and addgroup. You may wish to call the user and group something else instead of mysql.
Unpack the distribution into the current directory:
shell> gunzip < /path/to/mysql-VERSION.tar.gz | tar xvf -

This command creates a directory named `mysql-VERSION'.
Change into the top-level directory of the unpacked distribution:
shell> cd mysql-VERSION

Note that currently you must configure and build MySQL from this top-level directory. You can not build it in a different directory.
Configure the release and compile everything:
shell> ./configure --prefix=/usr/local/mysql
shell> make

When you run configure, you might want to specify some options. Run ./configure --help for a list of options. If configure fails, and you are going to send mail to
mysql@lists.mysql.com to ask for assistance, please include any lines from `config.log' that you think can help solve the problem. Also include the last couple of lines of output from configure if configure aborts. Post the bug report using the mysqlbug script.
Install everything:
shell> make install

You might need to run this command as root.
Create the MySQL grant tables (necessary only if you haven't installed MySQL before):
shell> scripts/mysql_install_db

Note that MySQL versions older than Version 3.22.10 started the MySQL server when you run mysql_install_db. This is no longer true!
Change ownership of the installation to the user that you will run mysqld as:
shell> chown -R mysql /usr/local/mysql
shell> chgrp -R mysql /usr/local/mysql

The first command changes the owner attribute of the files to the mysql user, and the second changes the group attribute to the mysql group.

If you would like MySQL to start automatically when you boot your machine, you can copy support-files/mysql.server to the location where your system has its startup files. More information can be found in the support-files/mysql.server script itself.

After everything has been installed, you should initialize and test your distribution:
shell> /usr/local/mysql/bin/safe_mysqld --user=mysql &

If that command fails immediately with mysqld daemon ended then you can find some information in the file `mysql-data-directory/'hostname'.err'. The likely reason is that you already have another mysqld server running.