Relational Data Base Management System (RDBMS) is a database management system that is based on the relational model as invented by Edgar F. Codd, of IBM’s San Jose Research Laboratory. In 2017, many of the databases in widespread use are based on the relational database model.
RDBMS data is structured in database tables, fields and records. Each RDBMS table consists of database table rows. Each database table row consists of one or more database table fields.
RDBMS store the data into collection of tables, which might be related by common fields (database table columns). RDBMS also provide relational operators to manipulate the data stored into the database tables. Most RDBMS use SQL as database query language.
Popular RDBMS are MS SQL Server, DB2, Oracle and MySQL.
Features of RDBMS
- Offers information to be saved in the tables
- Numerous users can access it together which is managed by a single user
- Virtual tables are available for storing the insightful data
- In order to exclusively find out the rows, the primary key is used
- The data are always saved in rows and columns
- To retrieve the information the indexes are used
- Columns are being shared between tables using the keys
- Data is only stored once so multiple documentation changes are not required
- Better safety measures
- The table arrangement is straightforward and simple for database users to appreciate and use.
- It’s permit numerous database users to admittance a database concurrently.
- It’s agree to the database manager to limit admission to certified users, and gift rights to entity users depending on the kinds of database work they do
- It’s offer admission to the database via a server daemon, a dedicated software program that responds to requirements on a set of connections, and enables database users to connect and make use of the database.
- It’s feature safeguarding supply database managers with tools to without difficulty preserve analysis, revamp and back up the data centers.
- It’s support SQL language.
Primary and Foreign Keys
Primary key: The primary key finds out the similarity in the relationship. For the entire table, there is only one primary key. Every table has got a particular primary key which cannot be shared by other tables.
Foreign key: The foreign key is a key used for a different table of data which is referred by the primary key. There are many foreign keys for a single table. It depends on the primary key and its decision so as to refer those foreign keys to the table. Every foreign key can be shared and it speaks about the coordination among the data of different tables.
What is Table ?
In Relational database, a table is a collection of data elements organised in terms of rows and columns. A table is also considered as convenient representation of relations. But a table can have duplicate tuples while a true relation cannot have duplicate tuples. Table is the most simplest form of data storage. Below is an example of Employee table.
What is a Record ?
A single entry in a table is called a Record or Row. A Record in a table represents set of related data. For example, the above Employee table has 4 records. Following is an example of single record.
What is Field ?
A table consists of several records(row), each record can be broken into several smaller entities known as Fields. The above Employee table consist of four fields, ID, Name, Age and Salary.
What is a Column ?
In Relational table, a column is a set of value of a particular type. The term Attribute is also used to represent a column. For example, in Employee table, Name is a column that represent names of employee.
The NULL value of the table specifies that the field has been left blank during record creation. It is totally different from the value filled with zero or a field that contains space.
There are the following categories of data integrity exist with each RDBMS:
Entity integrity: It specifies that there should be no duplicate rows in a table.
Domain integrity: It enforces valid entries for a given column by restricting the type, the format, or the range of values.
Referential integrity: It specifies that rows cannot be deleted, which are used by other records.
User-defined integrity: It enforces some specific business rules that are defined by users. These rules are different from entity, domain or referential integrity.