EXISTS Operator:
Exists operator is a special type of operator which is used in a subquery. It is used to check whether a subquery returns something or not. If a subquery returns some row then outer query get executed otherwise the whole query will return nothing.
Syntax:
SELECT columnname(s)FROM tablenameWHERE EXISTS(SELECT *FROM tablename2"WHERE "condition");
SELECT columnname(s)
FROM tablename
WHERE EXISTS
(SELECT *
FROM tablename2"
WHERE "condition");
We can use EXISTS operator with DELETE , UPDATE OR DELETE statements other than SELECT statement.
Example:
SELECT *FROM EmployeeWHERE EXISTS (SELECT * FROM Payroll WHERE Employee.Emp_id = Payroll.P_id);
SELECT *
FROM Employee
WHERE EXISTS (SELECT *
FROM Payroll
WHERE Employee.Emp_id = Payroll.P_id);
This query will return rows only if the inner query will get executed successfully (return some data).
Example of Exists operator with Delete query:
DELETE FROM Employee WHERE EXISTS (SELECT * FROM Payroll WHERE Payroll.p_id = Employee.Emp_id);
DELETE FROM Employee WHERE
EXISTS (SELECT * FROM Payroll WHERE
Payroll.p_id = Employee.Emp_id);
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