How is the “exist” function used in SQL?

In SQL, the EXISTS is a predicate function used to check if there are any rows that meet specific conditions. Its syntax is as follows:

SELECT column1, column2, ...
FROM table_name
WHERE EXISTS (subquery);

In the above mentioned syntax, a subquery is a nested query used to specify the conditions that need to be checked. If the subquery returns a result set, EXISTS returns TRUE, otherwise it returns FALSE.

For example, suppose there is a table called Students, with columns named id and name. To check if a student record with id 1 exists, we can use EXISTS as follows:

SELECT *
FROM Students
WHERE EXISTS (SELECT 1 FROM Students WHERE id = 1);

If there is a student record with id 1, the above query will return the result; otherwise, it will not return any result.