step1：使用vidio_id相等的条件，将user_view_tb左连接vidio_info_tb得到两个新表t1和t2;

step2: 将t1和t2按照user_id相等，并且t1中的视频类型为鬼畜，t2中的视频内容为汽车进行连接；

step3: t2中user_id不为空的个数即为鬼畜区的用户里看过汽车的个数。

SELECT count(distinct t2.user_id) as num

FROM

(SELECT user_id, view_date, video_name, video_type

from user_view_tb a

left join video_info_tb b

on a.video_id=b.video_id

)t1

left join

(SELECT user_id, view_date, video_name, video_type

from user_view_tb a

left join video_info_tb b

on a.video_id=b.video_id

)t2

on t1.user_id=t2.user_id and t1.video_type='鬼畜' and t2.video_type='汽车'

where t2.user_id is not NULL;