SQL and DBMS

What are the three main normal forms

• 1NF (NF = Nominal Form)

• 2NF

• 3NF

Define the primary focus of 1st Nominal Form (1NF)

Atomic values and no repeating groups

Define the primary focus of 2nd Nominal Form (2NF)

Must be in 1NF and have no partial dependencies (all attributes must depend on the full primary key)

Define the primary focus of 3rd Nominal Form (3NF)

Must be in 2NF and have no transitive dependencies (attributes depend only on the primary key, not other non-key attributes)

What is the difference between an INNER JOIN and a LEFT JOIN

INNER JOIN Returns only the rows where there is a matching value in both tables, whereas

LEFT JOIN Returns all rows from the left table, and matching rows from the right table. If no match exists, it returns NULL for the right table columns.

When should you use a Hash Index versus a B-Tree Index