SQL从入门到实战-2

高级语句

窗口函数

排序窗口函数

例题二十九

select yr,party,votes,
rank() over (PARTITION BY yr ORDER BY votes desc) as pson
from ge 
where constituency = 'S14000021' 
order by party,yr

偏移分析函数

例题三十

select name,date_format(whn,'%Y-%m-%d') data,
confirmed 当天截止时间累计确诊人数,
lag(confirmed,1) over (partition by name order by whn) 昨天截止时间累计确诊人数,
(confirmed - lag(confirmed,1) over (partition by name order by whn)) 每天新增确诊人数
from covid
where name in ('France','Germany') and month(whn) = 1
order by whn

总结

练习题

1

select party,votes,
rank() over (order by votes desc) as pson
from ge
where constituency = 'S14000024' and yr = 2017
order by party

2

SELECT 
    name,
    confirmed AS 确诊人数,
    RANK() OVER (ORDER BY confirmed DESC) AS 确诊人数排名,
    deaths AS 死亡人数,
    RANK() OVER (ORDER BY deaths DESC) AS 死亡人数排名
FROM 
    covid
WHERE 
    whn = '2020-04-20'
ORDER BY 
    confirmed DESC;

3

select name,date_format(whn,'%Y-%m-%d') date,
(confirmed - lag(confirmed,1) over (order by whn)) New
from covid
where name = 'Italy' and WEEKDAY(whn) = 0
order by whn

表连接