SQL EXISTS - Learn2Done

To test the existence of any record in subquery EXISTS operator is used.

It returns a boolean value (True/False).

It returns True when the record is found in the subquery.

Syntax:

SELECT * FROM table_name
WHERE EXISTS
(SELECT column_name FROM table_name WHERE condition);

DEMO STUDENTS TABLE:

Data

Example: This SQL subquery will return True as Roll no. 2 is present in the table.

SELECT * FROM students
WHERE EXISTS
(SELECT Roll_No FROM students WHERE Roll_No = 5);

This will select the full table as the condition is True:

Data