Clickhouse 时间日期函数
注：所有的时间日期函数都可以在第二个可选参数中接受时区参数。示例：Asia / Yekaterinburg。在这种情况下，它们使用指定的时区而不是本地（默认）时区。
SELECT
toDateTime('2016-06-15 23:00:00') AS time,
toDate(time) AS date_local,
toDate(time, 'Asia/Yekaterinburg') AS date_yekat,
toString(time, 'US/Samoa') AS time_samoa
┌────────────────time─┬─date_local─┬─date_yekat─┬─time_samoa──────────┐
│ 2016-06-15 23:00:00 │ 2016-06-15 │ 2016-06-16 │ 2016-06-15 09:00:00 │
└─────────────────────┴────────────┴────────────┴─────────────────────┘
常用时间函数：
now() // 2020-04-01 17:25:40 取当前时间
toYear() // 2020 取日期中的年份
toMonth() // 4 取日期中的月份
today() // 2020-04-01 今天的日期
yesterday() // 2020-03-31 昨天的额日期
toDayOfYear() // 92 取一年中的第几天
toDayOfWeek() // 3 取一周中的第几天
toHour() //17 取小时
toMinute() //25 取分钟
toSecond() //40 取秒
toStartOfYear() //2020-01-01 取一年中的第一天
toStartOfMonth() //2020-04-01 取当月的第一天
formatDateTime(now(),'%Y-%m-%d') // 2020*04-01 指定时间格式
toYYYYMM() //202004
toYYYYMMDD() //20200401
toYYYYMMDDhhmmss() //20200401172540
dateDiff()
......
SELECT
toDateTime('2019-07-30 10:10:10') AS time,
-- 将DateTime转换成Unix时间戳
toUnixTimestamp(time) as unixTimestamp,
-- 保留 时-分-秒
toDate(time) as date_local,
toTime(time) as date_time, -- 将DateTime中的日期转换为一个固定的日期，同时保留时间部分。
-- 获取年份，月份，季度，小时，分钟，秒钟
toYear(time) as get_year,
toMonth(time) as get_month,
-- 一年分为四个季度。1（一季度:1-3）,2（二季度:4-6）,3（三季度:7-9）,4（四季度:10-12）
toQuarter(time) as get_quarter,
toHour(time) as get_hour,
toMinute(time) as get_minute,
toSecond(time) as get_second,
-- 获取 DateTime中的当前日期是当前年份的第几天，当前月份的第几日，当前星期的周几
toDayOfYear(time) as "当前年份中的第几天",
toDayOfMonth(time) as "当前月份的第几天",
toDayOfWeek(time) as "星期",
toDate(time, 'Asia/Shanghai') AS date_shanghai,
toDateTime(time, 'Asia/Shanghai') AS time_shanghai,
-- 得到当前年份的第一天,当前月份的第一天，当前季度的第一天，当前日期的开始时刻
toStartOfYear(time),
toStartOfMonth(time),
toStartOfQuarter(time),
toStartOfDay(time) AS cur_start_daytime,
toStartOfHour(time) as cur_start_hour,
toStartOfMinute(time) AS cur_start_minute,
-- 从过去的某个固定的时间开始，以此得到当前指定的日期的编号
toRelativeYearNum(time),
toRelativeQuarterNum(time);
获取未来时间的函数：
-- 第一种，日期格式（指定日期，需注意时区的问题）
WITH
toDate('2019-09-09') AS date,
toDateTime('2019-09-09 00:00:00') AS date_time
SELECT
addYears(date, 1) AS add_years_with_date,
addYears(date_time, 0) AS add_years_with_date_time;
-- 第二种，日期格式（当前，本地时间）
WITH
toDate(now()) as date,
toDateTime(now()) as date_time
SELECT
now() as now_time,-- 当前时间
-- 之后1年
addYears(date, 1) AS add_years_with_date,
addYears(date_time, 1) AS add_years_with_date_time,
-- 之后1月
addMonths(date, 1) AS add_months_with_date,
addMonths(date_time, 1) AS add_months_with_date_time,
--之后1周
addWeeks(date, 1) AS add_weeks_with_date,
addWeeks(date_time, 1) AS add_weeks_with_date_time,
-- 之后1天
addDays(date, 1) AS add_days_with_date,
addDays(date_time, 1) AS add_days_with_date_time,
--之后1小时
addHours(date_time, 1) AS add_hours_with_date_time,
--之后1分中
addMinutes(date_time, 1) AS add_minutes_with_date_time,
-- 之后10秒钟
addSeconds(date_time, 10) AS add_seconds_with_date_time,
-- 之后1个季度
addQuarters(date, 1) AS add_quarters_with_date,
addQuarters(date_time, 1) AS add_quarters_with_date_time;
获取过去时间的函数：
WITH
toDate(now()) as date,
toDateTime(now()) as date_time
SELECT
subtractYears(date, 1) AS subtract_years_with_date,
subtractYears(date_time, 1) AS subtract_years_with_date_time,
subtractQuarters(date, 1) AS subtract_Quarters_with_date,
subtractQuarters(date_time, 1) AS subtract_Quarters_with_date_time,
subtractMonths(date, 1) AS subtract_Months_with_date,
subtractMonths(date_time, 1) AS subtract_Months_with_date_time,
subtractWeeks(date, 1) AS subtract_Weeks_with_date,
subtractWeeks(date_time, 1) AS subtract_Weeks_with_date_time,
subtractDays(date, 1) AS subtract_Days_with_date,
subtractDays(date_time, 1) AS subtract_Days_with_date_time,
subtractHours(date_time, 1) AS subtract_Hours_with_date_time,
subtractMinutes(date_time, 1) AS subtract_Minutes_with_date_time,
subtractSeconds(date_time, 1) AS subtract_Seconds_with_date_time;
SELECT toDate('2019-07-31', 'Asia/GuangZhou') as date_guangzhou;
SELECT toDate('2019-07-31'), toDate('2019-07-31', 'Asia/Beijing') as date_beijing;
-- 亚洲只能加载上海的timezone？？？
SELECT toDateTime('2019-07-31 10:10:10', 'Asia/Shanghai') as date_shanghai;
计算连个时刻在不同时间单位下的差值
-- 第一种：指定时间计算差值示例
**WITH
toDateTime('2019-07-30 10:10:10', 'Asia/Shanghai') as date_shanghai_one,
toDateTime('2020-10-31 11:20:30', 'Asia/Shanghai') as date_shanghai_two
SELECT
dateDiff('year', date_shanghai_one, date_shanghai_two) as diff_years,
dateDiff('month', date_shanghai_one, date_shanghai_two) as diff_months,
dateDiff('week', date_shanghai_one, date_shanghai_two) as diff_week,
dateDiff('day', date_shanghai_one, date_shanghai_two) as diff_days,
dateDiff('hour', date_shanghai_one, date_shanghai_two) as diff_hours,
dateDiff('minute', date_shanghai_one, date_shanghai_two) as diff_minutes,
dateDiff('second', date_shanghai_one, date_shanghai_two) as diff_seconds;**
-- 第二种：本地当前时间示例
WITH
now() as date_time
SELECT
dateDiff('year', date_time, addYears(date_time, 1)) as diff_years,
dateDiff('month', date_time, addMonths(date_time, 2)) as diff_months,
dateDiff('week', date_time, addWeeks(date_time, 3)) as diff_week,
dateDiff('day', date_time, addDays(date_time, 3)) as diff_days,
dateDiff('hour', date_time, addHours(date_time, 3)) as diff_hours,
dateDiff('minute', date_time, addMinutes(date_time, 30)) as diff_minutes,
dateDiff('second', date_time, addSeconds(date_time, 35)) as diff_seconds;