Why are relationships different to joins?Review LaterRelationships only combine data when it is needed.Joins only combine data when it is needed.

The question seems to be asking about the difference between relationships and joins in the context of databases. Here's a step-by-step explanation:

1. Definition: A relationship in a database is a connection between two tables that are logically associated with each other. A join, on the other hand, is a method used to combine rows from two or more tables based on a related column between them.

2. Usage: Relationships are used to prevent data redundancy and to establish a connection between two tables so that the user can fetch data simultaneously from two or more tables. Joins are used to combine rows from two or more tables, based on a related column, which provides a meaningful result.

3. Data Combination: Relationships do not physically combine the data; they just create a link between two tables. Joins, however, physically combine the data from the tables, creating a new table as a result.

4. Performance: Since relationships do not physically combine the data, they can be more efficient in terms of performance. Joins, since they physically combine the data, can be less efficient, especially when dealing with large amounts of data.

5. Flexibility: Joins are more flexible than relationships. With joins, you can combine data from two tables in many ways, depending on the conditions you specify. With relationships, the way data is combined is determined by the type of relationship (one-to-one, one-to-many, many-to-many).

In conclusion, while relationships and joins in databases both involve combining data from two or more tables, they do so in different ways and are used for different purposes.