OracleÖм¸¸ö¹ØÓÚÈÕÆÚ·½ÃæµÄSQLʵÀý

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SQL> select to_char(sysdate,'YYYYMMDD W HH24:MI:SS') from
dual;

TO_CHAR(SYSDATE,'YY
-------------------
20030327 4 18:16:09

SQL> select to_char(sysdate,'W') from dual;

T
-
4 ¡í2:È¡µÃµ±Ç°ÈÕÆÚÊÇÒ»¸öÐÇÆÚÖеĵڼ¸Ìì,×¢ÖØÐÇÆÚÈÕÊǵÚÒ»Ìì
SQL> select
sysdate,to_char(sysdate,'D') from dual;

SYSDATE T
--------- -
27-MAR-03 5   ÀàËÆ: select to_char(sysdate,'yyyy') from dual;
--Äê
select to_char(sysdate,'Q' from dual; --¼¾
select to_char(sysdate,'mm') from dual; --ÔÂ
select to_char(sysdate,'dd') from dual; --ÈÕ
ddd ÄêÖеĵڼ¸Ìì
WW ÄêÖеĵڼ¸¸öÐÇÆÚ
W ¸ÃÔÂÖеڼ¸¸öÐÇÆÚ
D ÖÜÖеÄÐÇÆÚ¼¸
hh Сʱ(12)
hh24 Сʱ(24)
Mi ·Ö
ss Ãë ¡í3:È¡µ±Ç°ÈÕÆÚÊÇÐÇÆÚ¼¸ÖÐÎÄÏÔʾ:
SQL> select
to_char(sysdate,'day') from dual;

TO_CHAR(SYSDATE,'DAY')
----------------------
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alter session
set NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS'
¡í5: µÃµ½µ±Ç°µÄÈÕÆÚ
select sysdate from dual; ¡í6: µÃµ½µ±ÌìÁ賿0µã0·Ö0ÃëµÄÈÕÆÚ
select trunc(sysdate) from dual; -- µÃµ½ÕâÌìµÄ×îºóÒ»Ãë
select trunc(sysdate) + 0.99999 from dual; -- µÃµ½Ð¡Ê±µÄ¾ßÌåÊýÖµ
select trunc(sysdate) + 1/24 from dual; select trunc(sysdate) + 7/24
from dual; ¡í7:µÃµ½Ã÷ÌìÁ賿0µã0·Ö0ÃëµÄÈÕÆÚ
select trunc(sysdate+1)
from dual; select trunc(sysdate)+1 from dual;
¡í8: ±¾ÔÂÒ»ÈÕµÄÈÕÆÚ
select trunc(sysdate,'mm') from dual;
¡í9:µÃµ½ÏÂÔÂÒ»ÈÕµÄÈÕÆÚ
select trunc(add_months(sysdate,1),'mm') from dual; ¡í10:·µ»Øµ±Ç°ÔµÄ×îºó
Ò»Ìì?
select last_day(sysdate) from dual;       
select last_day(trunc(sysdate)) from dual;
select trunc(last_day(sysdate)) from dual;
select trunc(add_months(sys