Fundamentals of RDBMS

• In RDBMS, a table(Relation) organizes data into rows and columns.
• The columns are known as attributes.
• The rows are known as records/tuples.
• Consider the Student Table here. student-id, name, city and age are the attributes.
• Student table is a relation.
  • Formally relation is a set of tuples.
  • Which means no duplicate tuple is allowed.
• Each table has a unique primary key that identifies the information in a table.

Relationship

• The relationship between tables can be set via the use of foreign keys.
  • A field in a table that links to the primary key of another table is what is known as a Foreign Key.
  • Here Student table and Course table are brought into the Enrollment table.
  • For each student, the course he took and the marks that he obtained are included in the Enrollment table.
  • Student-id is the primary key of the Student table.
  • Course-id is the primary key of the Course table.
  • Student-id and Course-id columns from ‘Enrolment Table’ are foreign keys. (Both becomes foreign keys for the enrollment table.)
  • When put together, Student-id and Course-id will form the primary key of the Enrollment table.

yellow - primary key

red - foreign key

Index ⚡

One important feature that is required by a DBMS is the ability to fetch a record faster. Indexes support that feature.

• Index.
  • Indexing is used to optimize the performance of a database by minimizing the number of disk accesses.
  • The index is a type of data structure.
  • It is used to locate and access the data in a database table quickly.