1.601体育馆的人流量-困难

1）使用lead和lag

2）id-row_number

2.620有趣的电影-简单

select * from cinema 
where description<>'boring'
and id%2<>0
order by rating desc

3.626换座位-中等

1）case

2）位操作

3）lag和lead

4.627变更性别

update Salary set 
sex = case sex 
when "m" 
then "f"
else "m"
end;
or
update Salary set sex = if(sex="m", "f", "m")

5.1179重新格式化部门表

group by+sum