Database Management System from scratch - Part 1

Explain how to compute the cardinality ratio between students and courses from the enrollment relationship, deriving N:M or N:1 based on max per-student and per-course counts.

Identify whether a relationship is one-to-one, many-to-one, or many-to-many in database design, using the employee–manager example to show a manager can oversee at most one employee.

Explore how a super key uniquely identifies a tuple using one or more attributes, and why every superset of a super key is also a super key.

Distinguish super keys from keys by defining minimal super keys, and learn how deleting attributes tests minimality to identify a true key in a relation.

The lecture shows that if ac is the only key, every super key must include ac, giving four super keys: ac, acb, acd, and acbd.

Explore how primary keys uniquely identify tuples and cannot be null, while foreign keys may reference other attributes and accept null values in relational databases.

Explore how insertion into relational tables may violate domain, key, entity integrity, and referential constraints, with examples like invalid ages, duplicate keys, null primary keys, and department references.

Learn to convert a one-to-one ER diagram relationship to a relational model by using foreign keys or a joint table, and understand primary keys and null values.

Choose primary key placement carefully in one-to-one relationships to minimize nulls and prioritize maximum cardinality over participation when possible. For many-to-many, create a new junction table to avoid multi-valued attributes.

Show how a closure like AB+ or C+ can include all attributes, making AB a superkey but not a key, while a single attribute that determines all is a key.