DBMS

Stands for “Database Management System”. Data has now become a key component of any organization. Database is a collection of related data. Data are the known facts that can be recorded and that have implict meaning. It can be text, images, audio, video and so on. Companies use their business data to analyze their economic health and create business strategies. Data present in customer reports, market surveys, client data and stakeholder information needs to be managed properly.

This is where a Database Management System comes in. It is used for collecting, storing, processing and retrieving data.

DBMS = data + set of programs to access/manipulate data.
DBMS is a collection of program that enables user to create and maintain a database.

An RDMS is an advanced version of it.

What is RDBMS?

Stands for “Relational Database Management System”. An RDBMS is a DBMS designed specifically for relational databases. Therefore, RDBMSes are a subset of DBMSes. A relational databases refers to a database that stores data in a structured format, using rows and columns. This makes it easy to locate and access specific values within the database. It is “relational” because the values within each table are related to each other. Tables may also be related to other tables. The relational structure makes it possible to run queries across multiple tables at once.

All modern database Management Systems like SQL, MS SQL Server, IBM DB2, ORACLE, MY-SQL and Microsoft Access are based on RDBMS.
Examples of non-relational databases include Apache HBase, IBM Domino, and Oracle NoSQL Database. These type of databases are managed by other DMBS programs that support NoSQL, which do not fall into the RDBMS category.

Brief history of RDBMS

During 1970 to 1972, E.F. Codd published a paper to propose the use of relational database model.Its dominated the database market since the mid-1990s.

Terms used in relational database management system

1. Table
   The RDBMS database uses table to store data. A table is a collection of related data entries and contains rows and columns to store data. It is the simplest example of data storage in RDBMS. A table is also considered as convenient representation of relations. But a table can have duplicated tuples while a true relation cannot have duplicate tuples.

2. Field
   Every table is broken up into smalller entities called fields. A field is a column in a table that is designed to maintain specific information about every record in the table.

3. Row or Record
   A row of a table is called a record. It contains the specific information of each individual entry in the table.It is a horizontal entity in the table.

4. Column
   A column is a vertical entity in the table which contains all information associated with a speciic field in a table.

Before creating these tables, the RDBMS must check the following constraints:

• Primary keys – This identifies each row in the table. One table can only contain one primary key. The key must be unique and without null values.
• Foreign keys – This is used to link two tables. The foreign key is kept in one table and refers to the primary key associated with another table.
• Not null – This ensures that every column does not have a null value, such as an empty cell.
• Check – This confirms that each entry in a column or row satisfies a precise condition and that every column holds unique data.
• Data integrity – The integrity of the data must be confirmed before the data is created.

How RDBMS works?

Data is represented in terms of tuples(rows) in RDBMS. Relational database is most commonly used database. It contains number of tables and each table has its own primary key.Table is also known as relation. Due to a collection of organized set of tables, data can be accessed easily in RDBMS.

Tables in the relational database can be connected in diferent ways, such as:
- A record in one table could be related to another record in a different table (1:1 relationship)
- A record in one table may be related to several records in other tables (1:M relationship)
- Several table records could be linked to multiple records in a different table (M:N relationship)

However, before tables are created, a relational database management system must ensure that:
- Each table has a unique primary key, which has no null values.
- The foreign key, which is used to relate to 2 tables, is preserved in one table and refers to the primary key of another table.
- No column has a null value (empty cell).

Above, picture represent the relation between two tables. The table-name Department(dept) can have many employee(emp). The primary key of table-name : dept is the foreign key of the table-name : emp. So, we can see relation between two tables are one-to-many relationship.

DBMS VS RDBMS

DBMS (Database Management System) and RDBMS (Relational Database Management System) are both used for the storing information in the form of physical databases. DBMS is a combination of interrelated data and a group of programs for accessing that data.

On the other hand, RDBMS is the type of DBMS that has been designed to take care of the inefficiencies of DBMS.

1. In DBMS, data is stored in a file whereas RDBMS data is stored in the form of tables.
2. The best of RDBMS is that it support multiple users. DBMS support only one user
3. Relational databases always follow the ACID model while storing data. Hence, inconsistencies are reduced.In DBMS we can see inconsistencies in the data. It doesn’t follow ACID property to store data.
4. Access of data is more difficult in DBMS whereas In RDBMS data elements can be easily accessed using SQL queries. You can also access multiple data elements with ease.
5. There is no relationship between different data elements in a DBMS. In RDBMS, data is stored in the form of tables which are related to each other using foreign keys.
6. DBMS does not support integrity constants. These constants cannot be applied at the file levels.RDBMS supports integrity constraints. The support is provided at the schema levels. Values beyond a specific range cannot be stored in a particular RDMS column.

Advantage of RDBMS

• Easy to use
• Secured in nature
• Data manipulation can be done
• It offers logical database independence i.e. data can be viewed in different ways by the different users.
• It provides better backup and recovery procedures.
• Multiple users can access the database which is not possible in DBMS.

Disadvantage of RDBMS

• Requires skilled human resources to implement
• Difficult to recover the lost data
• Complex software refers to expensive hardware and hence increases overall cost to avail the RDBMS service.
• Software is expensive.
• Certain applications are slow in processing.

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