Ron is in the process of designing tables for a database that will contain information for all school matches played in a year. What kind of a field must he define to prevent users from entering duplicate values?

The main idea of a database design is normalization. This process is about repeating data as little as possible. There are different levels of normalization but for now lets just look at the basics. If a students name is Jane Doe and she legally gets her named changed because of her mother getting remarried; what happens if you need to look her up in the database? If you do not have an ID then if her name is changed to Jane Smith she would not be found. But if she had an ID such as 492943 and you do a lookup by id if her name changes it will not affect related records. If you have a user table with permissions and store roles in plain text, what if you need to change the role name? That leaves room for error. But if you have a roles table with id's than in the role field of the users table it is just referencing and ID called a foreign key