oracle数据库取日期

oracle取月初月末日期
select last_day(add_months(sysdate,-2))+1 as "上个月第一天",last_day(add_months(sysdate,-1)) as "上个月最后一天"  from dual;

select trunc(sysdate, 'mm') "当月第一天" from dual;
select trunc(add_months(sysdate,-1), 'mm') "上个月第一天" from dual;
select last_day(add_months(sysdate,-1)) "上个月最后一天" from dual;

select to_char('2022-02-19') as "当前时间是周六",next_day(to_date('2022-02-19','yyyy-mm-dd'),2) as "下周一" from dual;
select to_char('2022-02-19') as "当前时间是周六",next_day(to_date('2022-02-19','yyyy-mm-dd'),2)-7 as "本周一" from dual;

select trunc(sysdate,'iw') as "本周一"from dual;
select trunc(sysdate,'iw')-7 as "上周一"from dual;
select trunc(sysdate,'iw')+7 as "下周一"from dual;
select to_char(sysdate,'q') from dual   --季
select to_char(sysdate,'yyyy') from dual --年
select to_char(sysdate,'mm') from dual--月
select to_char(sysdate,'dd') from dual --日
select to_char(sysdate,'d') from dual --星期中的第几天
select to_char(sysdate,'DAY') from dual --星期几
select to_char(sysdate,'ddd') from dual --一年中的第几天

pg数据库取日期

pg数据库

select date_trunc('year',now()) --取年初
select date_trunc('month',now()) --取月初
select date_trunc('day',now())  --取当日日期

select date_part('year',now()) --取年字段
select date_part('months',now()) --取月字段
select date_part('days',now()) --取日字段

select now()+interval'-1 weeks' --上周

SELECT EXTRACT(YEAR FROM now()) FROM RK --从now()字段中提取年份
SELECT EXTRACT(MONTH FROM now()) FROM RK --从now()字段中提取月份
SELECT EXTRACT(DAY FROM now()) FROM RK --从now()字段中提取日
SELECT EXTRACT(HOUR FROM now()) FROM RK --从now()字段中提取时
SELECT EXTRACT(MINUTE FROM now()) FROM RK --从now()字段中提取分
SELECT EXTRACT(SECOND FROM now()) FROM RK --从now()字段中提取秒