Normal Form - Shekharrajak/StackRoute_Files GitHub Wiki

1 NF

Must have single value in each cell

2 NF

All fields must be depend on one field - primary key.

3 NF

Means one field must not depend on other than primary key. Only primary key must be able to determine the field.

4 NF

No multi value dependency. It reduces the redundancy.

5 NF

Fifth normal form (5NF), also known as project-join normal form (PJ/NF) is a level of database normalization designed to reduce redundancy in relational databases recording multi-valued facts by isolating semantically related multiple relationships. A table is said to be in the 5NF if and only if every non-trivial join dependency in that table is implied by the candidate keys.

A join dependency *{A, B, … Z} on R is implied by the candidate key(s) of R if and only if each of A, B, …, Z is a superkey for R.[1]

SELECT t3.Class, t3.Subject, t1.Lecturer
FROM TABLE3 t3, TABLE3 t2, TABLE3 t1,
where t3.Class = 'SEMESTER1' and t3.SUBJECT= 'PHYSICS'
AND  t3.Subject = t1.Subject
AND t3.Class = t2.Class
 AND t1.Lecturer = t2.Lecturer;