SQL：postgresql中生成当前时间以及当前时间戳

生成当前时间​​select now()​​

只保留到秒数​​select now()::timestamp(0)without time zone​​

生成当前时间戳​​SELECT EXTRACT(epoch FROM now())​​

生成当前时间戳（保留到秒数）​​SELECT EXTRACT(epoch FROM now()::timestamp(0))​​

时间戳转时间​​SELECT TO_TIMESTAMP((SELECT EXTRACT(epoch FROM now()::timestamp(0))))​​

时间戳转时间（保留到秒数）​​SELECT TO_TIMESTAMP((SELECT EXTRACT(epoch FROM now()::timestamp(0))))::timestamp(0)​​

字符串类型时间转时间戳​​SELECT to_timestamp ( '2020-03-21 18:13:59', 'yyyy-MM-dd hh24:mi:ss' )​​

without time zone作用是不带时区