--获取指定时间的上一个月份
select substr((date_format((cast(date(cast('2021-12-23 23:59:59' as timestamp)) - interval '1' month as timestamp)),'%Y-%m-%d')),1,7)
--获取当前时间的上一个月份：
select substr((date_format((cast(current_date - interval '1' month as timestamp)),'%Y-%m-%d')),1,7)
--获取当前时间：
select substr(cast(now() as varchar),1,19); #输出格式：2021-12-24 15:37:26
-- 数据类型转化
cast(字段名 as 数据类型)
-- 类似mysql的ifnull() 判空转化
coalesce(va.balance_amount,0)
-- 时间戳转年月日时分秒，
date_format()用法：
select date_format(cast('2021-10-11 10:56:11' as timestamp),'%Y-%m-%d');
format_datetime()用法：
format_datetime(cast(m.handle_time as timestamp),'HH:mm:ss') == mysql的date_format(m.handle_time),'HH:mm:ss')
/*获取当前月份*/
SELECT month(cast(now() as timestamp));
select CAST(DATE_ADD('day',1-day(current_date),current_date)as varchar(20));/* 当月第一天 */
/* 取N天前的日期 */
select current_date - interval '30' day;
/* 取前N月的第一天、和最后一天 */
select date_format(cast(concat(substr('2021-01-11 00:00:00',1,7),'-01') as timestamp) - interval 'N' month,'%Y-%m-%d');
select date_format(cast(concat(substr('2021-01-11 00:00:00',1,7),'-01') as timestamp) - interval 'N' month + interval '1' month - interval '1' second ,'%Y-%m-%d %H:%i:%s');
/* 算两个日期时间之差，时间比较 */
for function date_diff. Expected:
date_diff(varchar(x), date, date) ,
date_diff(varchar(x), timestamp, timestamp) ,
date_diff(varchar(x), time, time) ,
date_diff(varchar(x), time with time zone, time with time zone) ,
date_diff(varchar(x), timestamp with time zone, timestamp with time zone)
date_diff('day',cast(s.buy_time as timestamp),cast(s.insurance_end_time as timestamp))
-- 前面是开始时间,后面是结束时间
-- presto分页查询
SELECT * FROM (
SELECT ROW_NUMBER() over(ORDER BY 1) as Row,T.* FROM (这里填入sql语句或者表名) as T) TT
WHERE TT.Row BETWEEN 1 AND 10000;
/* 字符串转整数int */
cast(字段 as int)
/* NVL以及NVL2函数 */
NVL（ comm,0) 如果字段comm为空返回0,不为空返回comm
NVL2(表达式1，表达式2，表达式3） 如果1为空，返回值为3。如果1不为空，返回值为2
/* 计算、保留小数 */
select cast(1 as decimal(10,4))/cast(3 as decimal(10,4)) as rate ;
