Final answer:
Tables can be joined using the primary key and foreign key relationship, any common column in either table, joining tables to themselves (self-join), or joining tables to other tables.
Step-by-step explanation:
The correct method to join tables in a database depends on the relationship between the tables. The most common method is to use the primary key in one table and a foreign key in another. This ensures that there is a proper relationship between the tables based on the primary and foreign key values. Additionally, tables can also be joined using any column in either table if there is a common attribute that can be used for the join. However, it is important to note that this method may not always be ideal and can result in incorrect or irrelevant data being joined.
Joining tables to themselves is also a valid method and is known as self-join. This is useful when you need to create a relationship within a single table. For example, if you have an employee table and want to find the manager for each employee, you can use a self-join on the employee table using the employee ID and the manager ID.
Finally, joining tables to other tables is the primary use case for table joins. This allows you to combine data from multiple tables based on a common attribute. For example, if you have a customer table and an order table, you can join them based on the customer ID to get information about the orders made by each customer.