1.該函數(shù)返回當(dāng)前的日期與時(shí)間,一般和dual偽表一起合作,

2.sysdate函數(shù)用于獲取數(shù)據(jù)庫(kù)所在的操作系統(tǒng)的當(dāng)前時(shí)間值的.

我們可以使用NLS_DATE_FORMAT參數(shù)或者TO_CHAR函數(shù)來(lái)獲得我們想要的SYSDATE日期格式，具體的格式代碼如下：

Format Code Explanation

YEAR	Year, spelled out
YYYY	4-digit year
MM	Month (01-12; JAN = 01).
MON	Abbreviated name of month.
MONTH	Name of month, padded with blanks to length of 9 characters.
D	Day of week (1-7).
DAY	Name of day.
DD	Day of month (1-31).
DDD	Day of year (1-366).
DY	Abbreviated name of day.
HH	Hour of day (1-12).
HH12	Hour of day (1-12).
HH24	Hour of day (0-23).
MI	Minute (0-59).
SS	Second (0-59).
SSSSS	Seconds past midnight (0-86399).

3.與sysdate不同,CURRENT_DATE()函數(shù)會(huì)返回?cái)?shù)據(jù)庫(kù)會(huì)話所設(shè)置的本地時(shí)區(qū)的當(dāng)前日期.

4.設(shè)置nls_date_format的時(shí)間格式

alter session set nls_date_format='YYYY-MM-DD HH24:MI:SS';

另外請(qǐng)注意SYSDATE函數(shù)的類型并非是DATE類型，而是其特有的類型:

    SQL> create table mytime(t1 date);

Table created.

SQL> insert into mytime values (sysdate);

1 row created.

SQL> commit;

Commit complete.

SQL> select dump(t1), dump(sysdate), dump( current_date) from mytime;

DUMP(T1)
--------------------------------------------------------------------------------
DUMP(SYSDATE)
--------------------------------------------------------------------------------
DUMP(CURRENT_DATE)
--------------------------------------------------------------------------------
Typ=12 Len=7: 120,111,8,24,21,31,59
Typ=13 Len=8: 219,7,8,24,20,32,12,0
Typ=13 Len=8: 219,7,8,24,20,32,12,0

以上可以看到sysdate和current_date都屬于TYPE=13，而普通DATE類型為TYPE=12
  

數(shù)據(jù)類型type=12代表DATE Valid date range from January 1, 4712 BC to December 31, 9999 AD.

11.26號(hào)----sysdate函數(shù)