oracle的sql改成mysql版本

oracle语句改写成mysql

 select nvl(sum(is_this_month),0)                        as total,               nvl((sum(is_this_month) - sum(is_last_month)),0) as                                                            month_count,               nvl((sum(is_today) - sum(is_last_day)),0)        as day_count        from (select case                         when to_char(TRUNC(SYSDATE - 1), 'dd') = to_char(VALID_DATE, 'dd') then 1                         else 0 end as                         is_last_day,                     case                         when to_char(sysdate, 'dd') = to_char(VALID_DATE, 'dd') then 1                         else 0 end as                         is_today,                     case                         when to_char(sysdate, 'MM') = to_char(VALID_DATE, 'MM') then 1                         else 0 end as                         is_this_month,                     case                         when to_char(TRUNC(add_months(trunc(sysdate), -1), 'MM'), 'MM') = to_char(VALID_DATE, 'MM')                             then 1                         else 0 end as                         is_last_month              from (SELECT *                    FROM API_SERVICE                    WHERE VALID_DATE is not null                      and VALID_DATE > TRUNC(ADD_MONTHS(sysdate, -1), 'mm'))) b

如何改写成mysql版本