How is the usage of “exist” in Oracle?

1 year ago
Jackson Davis
1 minute

In Oracle, EXISTS is a predicate function used to check if a subquery returns any rows. Its syntax is as follows:

EXISTS (subquery)

If the subquery returns at least one row, EXISTS will return TRUE; otherwise, it will return FALSE. Typically, EXISTS is used in conjunction with the main query in the WHERE clause to filter the result set of the main query based on the results of the subquery. For example:

SELECT * 
FROM employees
WHERE EXISTS (
    SELECT 1
    FROM departments
    WHERE employees.department_id = departments.department_id
);

The above query will return all employees in the departments table that have corresponding departments.

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