Lec-29: All Normal Forms with Real life examples | 1NF 2NF 3NF BCNF 4NF 5NF | All in One | Summary and Q&A

TL;DR

This video provides a summary of the first, second, third, BCNF, fourth, and fifth normal forms in database design, explaining the conditions and giving real-life examples for each.

Key Insights

• 🎯 First Normal Form (1NF): Attributes should be atomic, i.e., single-valued. No multi-valued attribute, such as storing multiple values in one column.
• 🔑 Second Normal Form (2NF): Table should be in 1NF and should not have partial dependency. Full dependency is required, where a unique attribute determines a non-unique attribute.
• 🌟 Third Normal Form (3NF): Table should be in 2NF and should not have transitive dependency. Transitive dependency occurs when a non-unique attribute is determined by another non-unique attribute through a unique attribute.
• 🔒 Boyce-Codd Normal Form (BCNF): Table should be in 3NF and the left-hand side of every dependency should be either a candidate key or a super key. BCNF eliminates maximum redundancy.
• 🔩 Fourth Normal Form (4NF): Table should be in BCNF and should not have multi-valued dependency. Multi-valued dependency occurs when multiple values of one attribute correspond to multiple values of another attribute.
• 🧩 Fifth Normal Form (5NF): Table should be in 4NF and should have a lossless decomposition. Lossless decomposition means that when a table is split into multiple tables, the common attribute should be a candidate key in at least one of the tables to avoid spurious tuples.
• 📚 Normalization summary videos provided are helpful for exams, interviews, and studying for any related exams.

Transcript

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Questions & Answers

Q: What are the conditions for a table to be in the second normal form?

The table should be in the first normal form, and there should be no partial dependencies, meaning that every non-prime attribute should be fully dependent on the entire candidate key. A real-life example of partial dependency is when multiple founders of a company together determine financial decisions, but one founder can make financial decisions alone without the help of others.

Q: What is the difference between the third normal form and the Boyce Codd normal form?

The third normal form requires the absence of transitive dependencies, where a non-prime attribute determines another non-prime attribute. In comparison, the Boyce Codd normal form extends the third normal form by specifying that the left-hand side of every dependency should be either a candidate key or a super key.

Q: What is a multi-valued dependency, and how can it be resolved?

A multi-valued dependency occurs when one attribute depends on multiple values of another attribute. To resolve this, the table can be decomposed into separate tables, each containing the common attribute and its dependent attribute, thereby eliminating the repetition and allowing each attribute to have a single value.

Q: What is the fifth normal form, and what does it require?

The fifth normal form, or the Project-Join normal form, requires that the table be in the fourth normal form and that the decomposition of the table into separate tables does not introduce any spurious tuples. This means that the common attribute used to divide the table must be a candidate key, ensuring a lossless decomposition.

Summary & Key Takeaways

• The first normal form requires that every attribute in a table be atomic or single-valued, with no multi-valued attributes.

• The second normal form states that the table should be in the first normal form and should have no partial dependencies, ensuring full dependencies between candidate keys.

• The third normal form builds on the second normal form by adding that there should be no transitive dependencies, where a non-prime attribute determines another non-prime attribute.

• The Boyce Codd normal form (BCNF) extends the third normal form by requiring that the left-hand side of every dependency is either a candidate key or a super key.

• The fourth normal form adds the condition that there should be no multi-valued dependencies, where one attribute depends on multiple values of another attribute.

• The fifth normal form, also known as the Project-Join normal form, introduces the requirement of lossless decomposition and the absence of joint dependencies.