Step-by-step explanation:
In a relational database, a candidate key is a column or a set of columns that can uniquely identify each row in a table. A table may have more than one candidate key, and here are a few examples of such tables:
Customer table: A customer table may have more than one candidate key, such as customer ID, email address, or phone number. Each of these columns can uniquely identify each customer in the table.
Employee table: An employee table may have more than one candidate key, such as employee ID, Social Security number, or email address. Each of these columns can uniquely identify each employee in the table.
Product table: A product table may have more than one candidate key, such as product ID, UPC code, or product name. Each of these columns can uniquely identify each product in the table.
Student table: A student table may have more than one candidate key, such as student ID, email address, or student number. Each of these columns can uniquely identify each student in the table.
Order table: An order table may have more than one candidate key, such as order ID, order date, or customer ID. Each of these columns can uniquely identify each order in the table.
In each of these examples, there are multiple columns that can uniquely identify each row in the table, and each of these columns can be used as a candidate key.