两种类型12和13

http://oraclesniplets.tumblr.com / post / 1179958393 / my-oracle-support-oracle-database-69028-1

类型13

 从双重选择dump（sysdate）; 
 Typ = 13 Len = 8：220,7,11,26,16,41,9,0 

日期数据类型的格式是

字节1  - 基数256年修正值：220 
 2  - 基数256年：256 * 7 = 1792 + 220 = 2012 
 3  - 月：11 
 4  - 日：26 
 5 - 时间：16 
 6  - 分钟：41 
 7  - 秒：09 
 8  - 未使用
 

2012-11-26 16:41:09

类型12

 从标签中选择转储（begindate） 
 Typ = 12 Len = 7：100,112,2,7,1,1,1 

日期数据类型的格式为

字节1  - 世纪（超出100）100  -  100 = 00 
字节2  - 年（超过100）112  -  100 = 12 
字节3  - 月= 2 
字节4  - 天= 7 
字节5小时（超出1）1  -  1 = 0 
字节6分钟（超出1）1  -  1 = 0 
字节7  - 秒（超出1）1  -  1 = 0 
 

0012-02-07 00:00:00

How are dates stored in Oracle? For example I know most systems use Epoch time to determine what time it is. By calculating how many seconds away from January 1st 1970. Does Oracle do this as well?

The reason I am asking this is I noticed if you take two dates in Oracle and subtract them you get a floating point of how many days are between.

Example

(Sysdate - dateColumn)

would return something like this (depending on the time)

3.32453703703703703703703703703703703704

Now is Oracle doing the conversion and spitting that format out, or does Oracle store dates with how many days it is away from a certain time frame? (Like Epoch time)

The are two types 12 and 13

http://oraclesniplets.tumblr.com/post/1179958393/my-oracle-support-oracle-database-69028-1

Type 13

select dump(sysdate) from dual;
Typ=13 Len=8: 220,7,11,26,16,41,9,0

The format of the date datatype is

Byte 1 - Base 256 year modifier : 220
2      - Base 256 year : 256 * 7 = 1792 + 220 = 2012
3      - Month : 11
4      - Day : 26
5      - Hours : 16
6      - Minutes : 41
7      - Seconds : 09
8      - Unused

2012-11-26 16:41:09

Type 12

select dump(begindate) from tab;
Typ=12 Len=7: 100,112,2,7,1,1,1

The format of the date datatype is

byte 1 - century (excess 100)  100 - 100 = 00
byte 2 - year (excess 100)  112 - 100 = 12
byte 3 - month = 2
byte 4 - day = 7
byte 5 - hour (excess 1) 1 - 1 = 0
byte 6 - minute (excess 1) 1 - 1 = 0
byte 7 - seconds (excess 1) 1 - 1 = 0

0012-02-07 00:00:00