select count(*),t.分组字段 from (
select t.* ,to_char(t.时间,'HH24') stime,to_char(t.时间,'HH24mi') fz,to_char(时间,'d') 
from A t
where 时间>=to_date('2019-12-01','yyyy-MM-dd') and ghsj=to_date('2019-12-31','yyyy-MM-dd') and to_char(时间,'d')='2'
) where stime in ('08','09','10','11','12') and fz>=0800 a 
group by T.分组字段

to_char(时间,'d') 取当前时间是星期几 每星期第一天为周日

to_char(t.时间,'HH24mi') 取当前时间的小时分

o_char(t.时间,'HH24') 取当前时间的小时

select max(t1.INVALID_TIME) from T_CUSTOMER t1 where t1.customer_code = '5101'

SELECT INVALID_TIME FROM (SELECT * FROM T_CUSTOMER WHERE customer_code='5101' ORDER BY INVALID_TIME desc) WHERE ROWNUM =1

select INVALID_TIME from T_CUSTOMER t where INVALID_TIME=(select max(INVALID_TIME) from T_CUSTOMER where customer_code='5101') and ROWNUM =1 

select INVALID_TIME from T_CUSTOMER t wheret.INVALID_TIME = (select max(t1.INVALID_TIME) from T_CUSTOMER t1 where t1.customer_code = '5101')