SELECT salary INTO @variable1 FROM employee_info WHERE emp_id = 12345678 LIMIT 1;
of
SET @variable1 = (SELECT salary FROM employee_info WHERE emp_id = 12345678 LIMIT 1);
SELECT @variable1;
SELECT salary INTO @variable1 FROM employee_info WHERE emp_id = 12345678 LIMIT 1;
of
SET @variable1 = (SELECT salary FROM employee_info WHERE emp_id = 12345678 LIMIT 1);
SELECT @variable1;