What is the usage of hints in SQL?

In SQL, hints are used to instruct the database optimizer on how to execute a query in order to improve query performance. Hints are a type of comment syntax that guides the database optimizer on how to execute a query to ensure the query is performed in the best possible way. Common hints include using indexes, enforcing join order, selecting join algorithms, and so on. Using hints in SQL queries can help optimize query performance, but they should be used carefully as incorrect hints can lead to a decrease in query performance. The syntax and types of hints supported may vary depending on the specific database management system.