RDBMS – Relational Database Management System, is a software system or collection of various programs that work together on a relational datamodel database and offer various integrated entities like – Database administration, Data definition, creation, updation etc. Some examples of RDBMS are –
RDBMS was introduced by E. F. Codd.
The basic structure of RDBMS revolves around tables like –
The data in RDBMS systems are stored inside tables.
The each row containing the data about a single entity in the entity set is called the record. This is also known as tuple as well.
Example –
For students studying in a university the entity is student and information about roll number 1 is stored in the a row which has values of all information like name, age, gpa year etc.
Column is all the values for a particular attribute for a table. This information is stored vertically.
For example – for students all the names as shown in the image will be the column.
Fields are nothing but the list of all possible attributes for the table. Roll_No, name, age, GPA, year all are fields.
Constraints in DBMS are various checks invoked by the system before an entry in a record. If it doesn’t match in that case data won’t be entered in the record itself. It is essential to maintain the integrity, authenticity and also sometimes security of the database.
The following are some constraints in SQL –