sql 查询统计数据，获取7天内数据

1.查询最近7天的数据

SELECT * FROM t_record  
where DATE_SUB(CURDATE(), INTERVAL 20 DAY) <= date(createdtime)
ORDER BY createdtime desc

2.查询最近7天内有数据的天数内，每天多少条数据

select date_format(createdtime,'%Y-%m-%d') as data, 
count(1) as count 
from t_record 
where createdtime >= date(now()) - interval 20 day 
group by day(createdtime);

返回结果，只包含有数据的天数

3.统计最近7天每天数据数量，没有数据则利用ifnull 补0

SELECT a.date ,IFNULL(b.count,0) as count
FROM(
SELECT CURDATE() as date
UNION ALL
SELECT DATE_SUB(CURDATE(),INTERVAL 1 day)as date
UNION ALL
SELECT DATE_SUB(CURDATE(),INTERVAL 2 day)as date
UNION ALL
SELECT DATE_SUB(CURDATE(),INTERVAL 3 day)as date
UNION ALL
SELECT DATE_SUB(CURDATE(),INTERVAL 4 day)as date
UNION ALL
SELECT DATE_SUB(CURDATE(),INTERVAL 5 day)as date
UNION ALL
SELECT DATE_SUB(CURDATE(),INTERVAL 6 day)as date
)a LEFT JOIN(
select date_format(createdtime,'%Y-%m-%d') as date, 
count(1) as count 
from t_record 
where createdtime >= date(now()) - interval 7 day 
group by day(createdtime)
)b on a.date = b.date
ORDER BY a.date desc