Primary Key:
A Primary Key in a
Example:
Students in Universities are assigned a unique registration number.
Therefore, in a STUDENT database table, the attribute “reg_no” acts as primary key.
Foreign Key:
Foreign Key is a column in a relational database table which provides a relation between two tables. It provides a cross reference between tables by pointing to primary key of another table.
Example:
In STUDENT database table, the attribute “reg_no” acts as primary key and in COURSE database table in which the student selects his or her course, the same “reg_no” acts as foreign key for the STUDENT table.
One to Many Relationship:
When one record in a database table is associated with more than one record in another table, the relationship between the two tables is referred as one to many relationship. It is also represented as1: M relationship. This is the opposite of many to one relationship.
ENTITY- RELATIONSHIP DIAGRAM (ERD):
Entity- Relationship Diagram is also known as ER Diagram. It is used to define the conceptual view of the database as viewed by the end user. It is used to depict the database’s main components: entities, relationships and attributes.
CROW FOOT ERD:
The Crow Foot ERD is an Entity Relationship Diagram which is used to represent the cardinalities present in the basic ER diagram. It is used to represent the relationships present between two tuples or tables present in the database.
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Chapter 3 Solutions
Database Systems: Design, Implementation, & Management
- Draw the relationships,identify the business rules,depicted in the Crow's foot ERD shown in the figure.arrow_forwardConsider Food item table attributes are food item key, food item and quantity. Time table attributes are year, quarter, month and day. Product table attributes are model name, model year, and category. Sales fact table attributes are sales dollars and sales quantity. Q.1 Design an appropriate schema for the above information Q.2 Create "dim" for the above information using the SQL statement. Q.3 Add attribute clause in the dimension clause. Q.4 Add “rollup” hierarchy in “dim” with appropriate levels and alter to add attribute.arrow_forwardCreate an ERD using Visio or any other tool for the following scenario. Your ERD should show all the tables, attributes for each table and identify all primary and foreign keys. A hair salon has many customers and many stylists - the first name, last name, and phone number need to be stored for customers and stylists. The hair salon offers many services - hair cutting, styling, coloring, permanents, etc. Each service has a cost and the estimated time. Customers schedule appointments with a stylist. The appointment can consist of one or more than one service - i.e. a person may want a hair cut and coloring. Some customers purchase products at their appointments. A product has a brand, description, category and price. Please show all work and the finished diagram. Thank you!arrow_forward
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