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DBMS 2NF

DBMS 2NF with DBMS Overview, DBMS vs Files System, DBMS Architecture, Three schema Architecture, DBMS Language, DBMS Keys, DBMS Generalization, DBMS Specialization, Relational Model concept, SQL Introduction, Advantage of SQL, DBMS Normalization, Functional Dependency, DBMS Schedule, Concurrency Control etc.

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Second Normal Form (2NF)

  • In the 2NF, relational must be in 1NF.
  • In the second normal form, all non-key attributes are fully functional dependent on the primary key

Example: Let's assume, a school can store the data of teachers and the subjects they teach. In a school, a teacher can teach more than one subject.

TEACHER table

TEACHER_ID SUBJECT TEACHER_AGE
25 Chemistry 30
25 Biology 30
47 English 35
83 Math 38
83 Computer 38

In the given table, non-prime attribute TEACHER_AGE is dependent on TEACHER_ID which is a proper subset of a candidate key. That's why it violates the rule for 2NF.

To convert the given table into 2NF, we decompose it into two tables:

TEACHER_DETAIL table:

TEACHER_ID TEACHER_AGE
25 30
47 35
83 38

TEACHER_SUBJECT table:

TEACHER_ID SUBJECT
25 Chemistry
25 Biology
47 English
83 Math
83 Computer

Next TopicDBMS 3NF




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