to_date , to_char

select sum(t.paid_fee)
         from order_payment_log t
        where to_char(to_date(t.edit_time, 'yyyy-MM-dd HH24:mi:ss'),
                      'yyyy-MM-dd') = to_char(sysdate, 'yyyy-MM-dd')
          and t.paid_state = 'Y';

to_char

to_char:将日期转换为字符串,

to_char(to_date(t.edit_time, 'yyyy-MM-dd HH24:mi:ss'),'yyyy-MM-dd')

将to_date 后的日期:2018-11-11 09:44:52转化为2018-11-11

to_char(sysdate, 'yyyy-MM-dd')将系统当前时间2018-11-11 09:44:52转为2018-11-11

to_date

to_date:将字符串转换为日期,

to_date(t.edit_time, 'yyyy-MM-dd HH24:mi:ss')

edit_time和yyyy-MM-dd HH24:mi:ss 格式要对应起来,否则报 文字与格式字符串不匹配错误


指定特定时间:

select sum(t.paid_fee)
         from order_payment_log t
        where to_char(to_date(t.edit_time, 'yyyy-MM-dd HH24:mi:ss'),
                      'yyyy-MM-dd') = '2018-11-10'
          and t.paid_state = 'Y';

to_char(sysdate, 'yyyy-MM-dd')目的就是手动的将时间定为:'2018-11-10'(指定的时间)