ORACLE函数-CSDN博客

tochar和todate

select　to_char(sysdate,'yyyymmdd')　from　dual;

结果：

TO_CHAR(SYSDATE,'YYYYMMDD')
　　
　　20030326

select　to_date('2003-12-12','yyyy-mm-dd')　from　dual;

结果：

TO_DATE('2003-12-12','YYYY-MM-DD')
2003-12-12

http://blog.chinaunix.net/u/25374/showart_195956.html

oracle中substr函数的用法

In oracle/PLSQL, the substr functions allows you to extract a substring from a string.

The syntax for the substr function is:

substr( string, start_position, [ length ] )
说明：
string is the source string.
start_position is the position for extraction. The first position in the string is always 1.
length is optional. It is the number of characters to extract. If this parameter is omitted, substr will return the entire string.
For example:

    substr ( 'This is a test' ,  6,  2)  would return  'is'
    substr ( 'This is a test' , 6) would return 'is a test'
    substr ( 'TechOnTheNet' , 1, 4) would return 'Tech'
    substr ( 'TechOnTheNet' , - 3, 3) would return 'Net'
    substr ( 'TechOnTheNet' , - 6, 3) would return 'The'
    substr ( 'TechOnTheNet' , - 8, 2) would return 'On'

DECODE的语法：

DECODE(value,if1,then1,if2,then2,if3,then3,...,else)，表示如果value等于if1时，DECODE函数的结果返回then1,...,如果不等于任何一个if值，则返回else。初看一下，DECODE 只能做等于测试，但刚才也看到了，我们通过一些函数或计算替代value，是可以使DECODE函数具备大于、小于或等于功能。