Primary Key and Foreign key Explained Using an Example. CPA Exam BAR. скачать в хорошем качестве

Primary Key and Foreign key Explained Using an Example. CPA Exam BAR.

In this video, I explain the primary key and foreign in a database setting as covered on the CPA exam. ✔️Accounting students and CPA Exam candidates, check my website for additional resources: https://farhatlectures.com/ 0:00 Introduction This video explains primary and foreign keys in relational databases, using an example of an electronic store's sales records. Here's a quick breakdown: Flat Files vs. Relational Databases (0:35): The video starts by discussing the limitations of flat files, such as data redundancy and difficulty in retrieving information, which leads to the need for relational databases. Creating Tables (3:27): The video explains how relational databases use tables for orders, customers, employees, and products. Primary Key (5:06): For each table, a primary key is created to uniquely identify each record. For example, a customer ID for the customer table (6:36). Foreign Key (7:23): The primary key from one table becomes a foreign key in another table to create relationships between the tables. For example, the customer ID in the order table. Benefits of Relational Databases (12:30): The video concludes by highlighting the benefits of relational databases, including scalability, complex queries, data integrity, and redundancy reduction. #cpaexam #cpaexaminindia #cpaevolution Primary keys and foreign keys are essential concepts in relational database design. They are used to establish and enforce relationships between tables, ensuring data integrity. 1. Primary Key (PK) Purpose: Uniquely identifies each record in a table. Characteristics**: Must contain a unique value for each row of data. Cannot contain `NULL` values. A table can have only one primary key, which may consist of single or multiple columns. It provides a way to ensure data in the specific column(s) is unique. Use case: If you have a `Users` table, each user might have a unique `UserID` which acts as a primary key. Physical Implementation: Often used as the basis for creating indexes, which helps speed up queries. 2. Foreign Key (FK) Purpose**: Used to establish and enforce a link between the data in two tables. Characteristics: A foreign key in one table points to a primary key in another table. Can contain duplicate values. Can contain `NULL` values if the relation is optional. A table can have multiple foreign keys depending on its relationships with other tables. It ensures referential integrity in the relation between two tables. If there is a foreign key defined, actions that would break references are typically rejected by the database. Use case: In an `Orders` table, there might be a `UserID` column as a foreign key linking each order to a user in the `Users` table. Physical Implementation: When defined, typically creates a database constraint, which can enforce behavior like cascade delete or update. An Example to Illustrate: Imagine a library database. There are two tables: `Books` and `Authors`. The `Authors` table might have: AuthorID (Primary Key) AuthorName DateOfBirth The `Books` table could have: BookID (Primary Key) Title AuthorID (Foreign Key pointing to AuthorID in the Authors table) Here, the `AuthorID` in the `Authors` table is the primary key, ensuring each author has a unique identifier. The same `AuthorID` in the `Books` table acts as a foreign key, connecting each book to its author. Through this design, if you wanted to find out who wrote a particular book, you'd use the foreign key relationship between the `Books` table and the `Authors` table. In summary, primary keys ensure uniqueness within their own table, while foreign keys create and enforce a relationship between two tables.