1767. 寻找没有被执行的任务对

![7{(]BNZDCSVZ8@N]NKY@XW.png

还是递归查询的使用，只不过这次里面有2个变量，另外尽量避免用not in, 用了经常超时

with recursive t(task_id, subtask_id) as
    (
    select task_id, subtasks_count from Tasks
    union all
    select task_id, subtask_id - 1 from t where subtask_id >= 2
    )
select t.* FROM t left join Executed E
on (t.task_id,t.subtask_id) = (E.task_id,E.subtask_id)
where E.task_id is null