1、NOW(), CURDATE(), CURTIME()的值

2、date_add(now(), interval 1 day) //当前时间加一天
date_sub(now(), interval 1 day) //当前时间减一天
3、简单函数
CASE [col_name] WHEN [value1] THEN [result1]…ELSE [default] END
搜索函数
CASE WHEN [expr] THEN [result1]…ELSE [default] END
4、最后写的sql
SELECT
SUM(CASE WHEN a.access_time BETWEEN DATE_SUB(NOW(), INTERVAL '3' DAY) AND NOW()
THEN 1 ELSE 0 END) AS "[0 ~ 3天]",
SUM(CASE WHEN a.access_time BETWEEN DATE_SUB(NOW(), INTERVAL '7' DAY) AND DATE_SUB(NOW(), INTERVAL '4' DAY)
THEN 1 ELSE 0 END) AS "[4 ~ 7天]",
SUM(CASE WHEN a.access_time BETWEEN DATE_SUB(NOW(), INTERVAL '15' DAY) AND DATE_SUB(NOW(), INTERVAL '8' DAY)
THEN 1 ELSE 0 END) AS "[8 ~ 15天]",
SUM(CASE WHEN a.access_time BETWEEN DATE_SUB(NOW(), INTERVAL '30' DAY) AND DATE_SUB(NOW(), INTERVAL '16' DAY)
THEN 1 ELSE 0 END) AS "[16 ~ 30天]"
FROM base_device_access_time_info a
5、结果
