Database Fundamentals: Keys, Relationships, and Normalization Concepts

Identify FK in ERD

A field that connects to another table's primary key

Foreign Key (FK)

A field that links one table to another by referencing a Primary Key

M:M Relationship

Many records in Table A relate to many in Table B (requires a junction table)

1:M Relationship

One record in Table A relates to many records in Table B

1:1 Relationship

One record in Table A relates to one record in Table B

Identify PK in ERD

The unique identifier in each entity (usually underlined or labeled)

Why use normalization?

To avoid duplicate data and improve data integrity

Why use a Foreign Key?

To create relationships between tables

Why use GROUP BY?

To summarize data (e.g., totals, counts)

Why use a Primary Key?

To uniquely identify each record in a table

When do you use HAVING instead of WHERE?

When filtering aggregated results (like COUNT or SUM)

Junction Table

A table used to break down a many-to-many relationship into two one-to-many relationships

Primary Key (PK)

A unique identifier for each record in a table (no duplicates, no nulls)

API

A way for different systems to communicate and exchange data (Application Programing Interface)

CRUD

Create, Read, Update, Delete (basic database operations)

Cardinality

Describes the relationship between tables (1:1, 1:M, M:N)

Referential Integrity

Ensures that foreign keys match existing primary keys (no broken links between tables)

Normalization

Organizing data to reduce redundancy and improve efficiency