SQL 差集计算的例子

SELECT a.assigned_to_workno from (SELECT DISTINCT(assigned_to_workno) from issue )  a
where a.assigned_to_workno not in 
(SELECT work_no FROM employee WHERE is_active = 'y');



SELECT * FROM issue WHERE assigned_to_workno in 
(SELECT a.assigned_to_workno from (SELECT DISTINCT(assigned_to_workno) from issue )  a
where a.assigned_to_workno not in 
(SELECT work_no FROM employee)
);