1 /*开始时间（以星期一为开始时间）：*/
 2 select  trunc(sysdate,‘D‘)+1  from  dual;
 3 
 4 /* 结束时间（以星期日为结束时间）：*/
 5 select trunc(sysdate,‘D‘)+7   from dual;
 6 
 7 /* 月初时间：*/
 8 select  trunc(sysdate,‘MM‘) from dual;
 9 
10 /* 月末时间：*/
11  select last_day(sysdate) from dual;
12  
13 /* 季初时间：*/
14 select trunc(sysdate,‘Q‘) from dual;
15 
16 /* 季末时间：*/
17 select add_months(trunc(sysdate,‘Q‘),3)-1 from dual;
18 
19 /*年初时间：*/
20 select trunc(sysdate,‘yyyy‘) from dual;
21 
22 /*年末时间：*/
23 select add_months(trunc(sysdate,‘yyyy‘),12)-1 from dual;
24 
25 /*一年中每月天数*/
26 select to_char(add_months(sysdate,-level+1),‘yyyy-mm‘) month, 
27 to_char(last_day(add_months(sysdate,-level+1)),‘dd‘) day from dual 
28 connect by level <=12
29 order by month
30 
31 /*一月中每天明细*/
32 select to_date(‘201809‘,‘yyyymm‘)+(rownum-1) s_date from dual  
33 connect by rownum<=last_day(to_date(‘201809‘,‘yyyymm‘)) - to_date(‘201809‘,‘yyyymm‘) + 1
34 order by s_date
35 
36 
37 /*到现在为止的12个月*/
38 select to_char(add_months(sysdate-360, rownum - 1),  ‘yyyy-mm‘) as monthlist from dual  
39 connect by rownum <= months_between(trunc(sysdate,‘mm‘),trunc(sysdate-360,‘mm‘))+1
40 order by monthlist
41 
42 /*月天数*/
43 select to_char(last_day(sysdate),‘dd‘) from dual;
44 select add_months(to_date(‘201801‘, ‘yyyymm‘),1)-to_date(‘201801‘, ‘yyyymm‘) from dual;