RDBMS Based on Codd's Relational Model

Relational Database Management System (RDBMS)

• RDBMS is based on the relational model introduced by E.F. Codd.
• Dr. Edgar F. Codd came up with 12 rules for a database to be considered a true relational database.

Codd's 12 Rules

• Rule 1: Information Rule - all data stored in a database must be a value of some table cell.
• Rule 2: Guaranteed Access Rule - every data element is guaranteed to be accessible logically with a combination of table-name, primary-key, and attribute-name.
• Rule 3: Systematic Treatment of NULL Values - NULL values must be given a systematic and uniform treatment.
• Rule 4: Active Online Catalog - the structure description of the entire database must be stored in an online catalog, known as a data dictionary.
• Rule 5: Comprehensive Data Sub-Language Rule - a database can only be accessed using a language with linear syntax that supports data definition, data manipulation, and transaction management operations.

Data Independence

• Logical data independence: data about the database, storing information about how data is managed inside.
• Physical data independence: the power to change the physical data without impacting the schema or logical data.

RDBMS Characteristics

• RDBMS stands for Relational Database Management Systems.
• Modern database management systems like SQL, MS SQL Server, IBM DB2, ORACLE, My-SQL, and Microsoft Access are based on RDBMS.
• RDBMS uses a tabular structure of data and supports relationships between data values.
• RDBMS supports distributed databases and can handle large amounts of data.

DBMS vs RDBMS

• DBMS is perhaps most useful for providing a centralized view of data that can be accessed by multiple users.
• RDBMS is an extension of DBMS and provides more convenience and efficiency to access data with high security.
• RDBMS applications store data in a tabular form, whereas DBMS applications store data as files.
• RDBMS defines the integrity constraint for the purpose of ACID (Atomicity, Consistency, Isolation, and Durability) property.

Data Integrity

• There are four categories of data integrity: entity integrity, domain integrity, referential integrity, and user-defined integrity.
• Entity integrity: no duplicate rows in a table.
• Domain integrity: enforcing valid entries for a given column by restricting the type, format, or range of values.
• Referential integrity: specifying that rows cannot be deleted, which are used by other records.
• User-defined integrity: enforcing specific business rules defined by users.

Examples of RDBMS

• MySQL
• PostgreSQL
• Oracle
• Microsoft Access
• Informix
• SQLite
• Amazon RDS
• MongoDB

Classful Addressing Scheme

• The classful A, B, and C octet boundaries were easy to understand and implement, but did not foster the efficient allocation of a finite address space.
• Classful network design served its purpose in the startup stage of the Internet, but lacked scalability in the face of the rapid expansion of the network in the 1990s.
• The class system of the address space was replaced with Classless Inter-Domain Routing (CIDR) in 1993.

Private IP Address and Public IP Address

• Private IP addresses are used within a local network and are invalid and non-routable in the Internet.
• Public IP addresses are used outside the local network and are provided by the Internet Service Provider (ISP).
• Private IP addresses are locally unique within a private network, while public IP addresses are globally unique across the Internet.

Servers

• Servers manage network resources such as hosting websites, transmitting data, sending or receiving emails, and controlling accesses.
• The purpose of a server is to provide services and features to clients, such as browsing websites, checking emails, and communicating with other users.
• Types of servers include:
  • Database servers: allow other computers to access a database and retrieve or upload data.
  • File servers: provide users with access to files and data stored centrally.
  • Web servers: deliver requested web pages to multiple client web browsers.
  • Mail servers: store and sort emails before they are sent to users upon request.
  • Application servers: provide an environment with all the necessary requirements to run or develop an application.

FTP Server

• FTP servers are used for file transfer and can provide connection to users without login credentials, but with limited access.
• Anonymous access is allowed, but uploading files to FTP servers is prohibited.
• FTP servers can also provide offsite backup of critical data and are inexpensive solutions for data transfer and backup operations.
• Secure FTP server options, such as SFTP and FTP/S, offer additional levels of security, including data encryption.

Database Server

• A database server refers to a combination of hardware and software that runs a database and provides database services.
• Database server works as a back-end portion for database applications, following the client-server model.
• It delivers all the information sought by client systems and is used by large-scale organizations that need to process large amounts of data regularly.

Types of Database Servers

• Database servers are also known as "Database Management System" or "Database Server Software".
• Types of database servers include relational models, which are based on first-order predicate logic and define a table as an n-ary relation.

ER Model

• An entity in an ER model is a real-world entity having properties called attributes.
• Every attribute is defined by its set of values called domain.
• Relationships among entities are mapped in various ways, including one-to-one, one-to-many, many-to-one, and many-to-many.

Relational Model

• The relational model is based on first-order predicate logic and defines a table as an n-ary relation.
• Data is stored in tables called relations.
• Relations can be normalized.
• In normalized relations, values saved are atomic values.
• Each row in a relation contains a unique value.
• Each column in a relation contains values from the same domain.