1. technology and computing
2. software
3. databases

ADMINISTRING DATABASE
SERVICES IN RED HAT LINUX
DATA BASE
DATA BASE TYPES
 MySQL
 PostgreSQL
Responsibilities of a DBA
1. Installing & maintaining database servers
 Installing patches
 Upgrading softwares
2. Installing & maintaining database clients
 Installing & maintaining client programs
3. Maintaining accounts and users.
 Adding /deleting users from the database
4. Ensuring Database security
 Access control
 permissions
5. Ensuring data integrity
 Protects data changes and avoids duplication in multiple users
FORMS OF DATABASE
1. Flat Files
Simple text files having



Space
Tab
Other characters
Example: /etc/passwd
2. Relations

The are also called RDBMS
Example: Spreadsheets
FLAT FILES
LIMITATIONS/ DISADVANTAGES
1. Do not scale well
Cannot perform random access on data
Search line by line (only sequential access)
2. Unsuitable for multi user environments.
Simultaneous changes by two users can lead to overwriting
RDBMS
ADVANTAGES
 Very good at finding relationships between data
 Stores data in tables with fields which makes
searching and sorting data easy.
SQL BASICS
 Database language
 Very similar to English and so it’s very simple
 SQL statements have a defined structure
 End users are unaware of it
CREATING A TABLE IDEA
 Different column types for data
 Special column types e.g DATE , VAR, VARCHAR
etc..
 SQL commands are not case sensitive
 Whitespace is generally ignored
 SQL statement terminates with a semi colon (;)
CREATING A TABLE . 1
 CREATE TABLE phonebook
 (Last_name VARCHAR (25) NOT NULL,
 First_name VARCHAR (25) NOT NULL,
 Phone INT (20) NOT NULL);
INSERTING VALUES
 INSERT INTO phonebook VALUES
(‘Doe’, ‘John’, ‘555-555-1212’);
TABLE VIEW
phonebook
Last_name
First_name
Phone
Doe
John
555-555-1212
Doe
Jane
555-666-1313
Pawl
John
123-456-7890
Johnson
Richard
111-222-3333
DISPLAYING DATA
 SELECT * FROM phonebook;
 SELECT first_name FROM phonebook;
 SELECT Last_name, Phone FROM phonebook;
 SELECT CONCAT(First_name, “ ” , Last_name) AS
Name FROM phonebook;
Name
John
Doe
Jane
Doe
John
Pawl
Richard Johnson
DISPLAYING DATA
 SELECT * FROM phonebook WHERE
first_name= “John”;
OPPOSITE
SELECT * FROM phonebook WHERE
first_name!= “John”;
CHOOSING A DATABASE:
MySQL V PostgreSQL
 SPEED:
MySQL is faster as compare to PostgreSQL.
Queries are executed and results are displayed faster
 Data Locking:
PostgreSQL is better then MySQL
MySQL locks the whole table when some one is
accessing a single field where as PostgreSQL just
locks the raw which is currently being accessed, the
rest whole table is open and unlock.
Locking table in MySQL and PostgreSQL
Last_name
First_name
Phone
Doe
John
555-555-1212
Doe
Jane
555-666-1313
Pawl
John
123-456-7890
Johnson
PostgreSQL
Richard
111-222-3333
PostgreSQL IS ACID COMPLIANCE
 Atomicity:
If you have a power failure or server crash after an original record has been
deleted but before the updated one has been added , you done lose the record
because atomic transaction ensure that the original record is not deleted unless
and untill the new record is added.
new record to be added(before crash)
Record recovered
Deleted old record before crash
PostgreSQL IS ACID COMPLIANCE
 Consistency:
Incomplete transactions are rolled back to maintain consistency.
 Isolation:
Ensures that multiple transactions operating on the same data are completely isolated
from each other. Prevents data corruption if two users try to write to the same record .
(locking )
 Durability:
If server crashed the database examines the
log file and makes the changes accordingly .
Procedural Languages
or
imperative language
PostgreSQL
, C++, JAVA , SQL
Programming Languages
PHP, Pearl, Visual Basic
Installing and configuring MySQL
 Two ways for installing and configuring
1- Source Version
2- Binary RPM (MySQL-server and MySQL-client)
i- Install it by rpm –i command.
ii- Initialize the grand tables by mysql_install_db command as root user.
iii- Go to mysql environment by typing mysql command .
iv- Setting a password for MySQL root user by mysql> SET PASSWORD FOR
root = PASSWORD (“secretword”); command inside mysql environment.
v- type exit command to exit mysql environment .
NOTE: Once installed through RPM , necessary user and group is created
automatically by the name MySQL .
Creating a database in MySQL
mysql> CREATE DATABASE animal;
OR
mysqladmin –u root –p create animals
Granting and Taking away Privileges in MySQL
 GRANT ALL ON animals.* TO usman IDENTIFIED BY ‘usman123’;
Database All table User
 REVOKE ALL on animals FROM usman;
Database
User
Password
Installing and configuring PostgreSQL
 Two ways for installing and configuring
1- Source Version
2- Binary RPM (postgresql, postgresql-server and postgresql-libs)
i- Install it by rpm –i command.
ii- Create the data directory by mkdir /usr/local/pgsql command as root user.
iii- Then change the user ownership of data directory to postgres user by typing chown postgres
/use/local/pgsql command as root user.
iv- Then change the group ownership of data directory to postgres group by typing chgrp postgres
/use/local/pgsql command as root user .
v- Then change your self to a postgres user by the command su- postgres in order to initialize
the data directories.
vi- To initialize give the command initdb –D /user/local/pgsql/data .
vii- Now start the database server by the command /usr/bin/postmaster –D /usr/local/pgsql/data
OR /usr/bin/pg_ctl -D /usr/local/pgsql/data –l logfile start
viii- At the end issue the command postmaster –D /usr/local/pgsql/data &
NOTE: Once installed through RPM , necessary user and group is created automatically by the
name postgres .
Creating a database in PostgreSQL
CREATE DATABASE animal;
OR
createdb animals
Creating a database user in PostgreSQL
CREATE USER usman;
OR
createuser usman
Deleting a database user in PostgreSQL
DROP USER usman;
OR
dropuser usman
Granting and Taking away Privilages in
PostgreSQL
 GRANT ALL ON animals TO usman ;
Database
User
 REVOKE ALL on animals FROM usman;
Database
User
Database clients
User
Database Client
Database Server
Database clients model 1
User
Your local host
Database Client
Database Server
Remote host
Database clients model 2
User
Your local host
Database Client
Database Server
Remote host 1
Remote host 2
Database clients model 3
User
Web Browser
Database Client
Web Server
Database Server
Your local host
Remote host 1
Remote host 2
Changing a database and getting help
mysql> help;
mysql> use animals;
database name