JOINs allow fetching related data in one query, avoiding multiple queries.
When you need to retrieve related data from multiple tables, using a JOIN can significantly reduce the number of database queries. Instead of querying the database separately for each related record (which can lead to the N+1 problem), a single JOIN query can fetch all related data at once. For example, if you want to retrieve a list of orders with their customer details, you can use a SQL JOIN to combine 'orders' and 'customers' tables in one query, reducing database load.
Additional Notes
How can JOINs help to prevent the N+1 query problem in JDBC?