EXISTS

SQL EXISTS Keyword

The EXISTS keyword is used to check whether a subquery returns any rows. It returns TRUE if the subquery produces one or more results.

SQL EXISTS Syntax

SELECT column1
FROM table1
WHERE EXISTS (
    SELECT column2
    FROM table2
    WHERE condition
);

SQL EXISTS Example

This example lists all doctors who have at least one appointment in the Appointments table.

SELECT first_name, last_name
FROM Doctors
WHERE EXISTS (
    SELECT appointment_id
    FROM Appointments
    WHERE Appointments.doctor_id = Doctors.doctor_id
);

SQL EXISTS Labs