Question

primary key-foreign key relationship.
I have exam tomorrow...Please help..

Answer 1

Primary Key-Foreign Key Relationships

To fully understand physical database models, it is important to understand the concepts behind primary key-foreign key relationships.

A primary key-foreign key relationship defines a one-to-many relationship between two tables in a relational database. A foreign key is a column or a set of columns in one table that references the primary key columns in another table. The primary key is defined as a column (or set of columns) where each value is unique and identifies a single row of the table.
Because of this primary key-foreign key relationship, you can join the Sales and Date tables to combine the other attributes of the Date table with the records in the Sales table. For example, if an analyst asks for the total sales, the day of the week, the product name, and the store in which the product was sold, the information is compiled by joining the sales, date, product, and store tables through the primary key-foreign key relationships between the Sales table and the various dimension tables.

Answer 2

in primary key unique value .and foreign key create if primary key refer some value