Relational Database - Codd's Rules

Relational Database - Codd's Rules !!!

A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd. Most popular commercial and open source databases currently in use are based on the relational database model.

A short definition of an RDBMS may be a DBMS in which data is stored in the form of tables and the relationship among the data is also stored in the form of tables.

Codd's Rules

• All database management must take place using the relational database's innate functionality
• All information in the database must be stored as values in a table
• All database information must be accessible through the combination of a table name, primary key and column name.
• The database must use NULL values to indicate missing or unknown information
• The database schema must be described using the relational database syntax
• The database may support multiple languages, but it must support at least one language that provides full database functionality (e.g. SQL)
• The system must be able to update all updatable views
• The database must provide single-operation insert, update and delete functionality




• Changes to the physical structure of the database must be transparent to applications and users.
• Changes to the logical structure of the database must be transparent to applications and users.
• The database must natively support integrity constraints.
• Changes to the distribution of the database (centralized vs. distributed) must be transparent to applications and users.
• Any languages supported by the database must not be able to subvert integrity controls.

Tags: database, table, DBMS, RDBMS, columns, Codd, E. F. Codd, rules, oracle, data

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Apt-Get command line tool

Apt-Get command line tool

(Ubuntu's Advanced Packaging Tool) !!!

The apt-get command is a powerful command-line tool used to work with Ubuntu's Advanced Packaging Tool (APT) performing such functions as installation of new software packages, upgrade of existing software packages, updating of the package list index, and even upgrading the entire Ubuntu system.

*Install package
#sudo apt-get install packagename

*Remove Package
#sudo apt-get remove packagename

*Install Multiple Packages
#sudo apt-get install packagename1 packagename2 packagename3

*Update the Package Index
#sudo apt-get update

The APT package index is essentially a database of available packages from the repositories defined in the /etc/apt/sources.list file.

*Upgrade the system
#sudo apt-get upgrade

*Read Debian APT User Manual
#sudo apt-get help

Tags: apt get apt-get advanced packaging tool install remove upgrade update help ubuntu linux unix package-management

Port Numbers - Linux

PORTS NUMBERS : Just as the physical address (MAC address) and the logical address (IP address) helps to route the traffic to a particular machine on a network, it is the port that identifies which service on the machine this traffic is destined to.

List of ports : /etc/services

A port on a specific computer is called a socket. It can be open, closed, listening or have a connection established.

###Important PORT NUMBERS to remember:

20 - FTP - data transfer

21 - FTP - control (command)

22 - SSH

23 - Telnet

25 - SMTP

37 - Time

43 - WHOIS

42 - WINS

53 - DNS

67 - BOOTp

68 - DHCP

69 - TFTP

79 - FINGER

80 - HTTP (WWW)

88 - Kerberose

101 - HOSTNAME

110 - POP3

111 - rpcbind

119 - NNTP

123 - NTP (Time)

137 - NetBios (nmbd)

139 - NetBios ( Samba)

143 - IMAP/Dovecot

161 - SNMP

180 - RIS

220 - IMAP3

389 - LDAP

443 - HTTPs

500 - Internet Key Exchange (IKE), IPSec

520 - RIP

546 - DHCPV6 client

547 - DHCPV6 server

554 - rtsp(Real Time Stream Protocol, Audio/Video)

631 - Printing (ipp)

744 - Flexlm

901 - SWAT

953 - rndc

993 - IMAPSecure

995 - POPs

999 - POP over SSL/TLS

2049 - NFS

2082 - CPANEL

2083 - CPANEL Secure SSL/TLS

2086 - CPANEL WHM

2087 - CPANEL WHM Secure/SSL

2095 - CPANEL Webmail

2096 - CPANEL Webmail Secure/SSL

2222 - Direct Admin Control Panel

2401 - CVSP server

3268 - AD Global Catalog

3269 - AD Global Catalog over SSL

3306 - MySQL Server

3389 - Terminal services (rdp-remote desktop protocol)

4643 - Virtusso Power Panel

(6000 - X11

6063)

8443 - Pleask Control Panel

9999 - Urchin

10000- Webmin Control Panel

21018- Skype

TAG: port, portnumber, port-numbers, tcp, udp, network, service, services, linux, socket, communication, transmission, dataflow, rhce, ubuntu, unix, red hat, red-hat, redhat