SQL练习 2022/7/4

197. 上升的温度

题干

代码思路

1. 使用日期比较函数

select  a.id 
from Weather a,Weather b
where DATEDIFF(a.recordDate , b.recordDate ) = 1 and a.Temperature >b.Temperature 
#或者
select  a.id 
from Weather a join Weather b
on  DATEDIFF(a.recordDate ,b.recordDate)=1 and a.Temperature >b.Temperature

511. 游戏玩法分析

题干
代码思路：

1. group by

select player_id,min(event_date) as  first_login 
from Activity
group by player_id

2. 排名函数一下

• 使用 dense_rank 函数按照 player_id 和 event_date 进行排序，并算出排名将其作为临时表 temp
• 查询临时表 temp，筛选出 排名 = 1 数据

select player_id, event_date as first_login from (
	select
		player_id,
		event_date,
		dense_rank()
		 over(partition by player_id order by event_date) as 排名
	from activity
) as temp where 排名 = 1;