oralce substr字符截取函数用法

在几乎所有的数据库教程中都会有字符截取这个函数，都大同小义了，下面我们来看看在Oralce中有个数据切割函数： substr的用法吧。

substr('要切割的值',从第几个位置开始切割,切割几位);

如下例：

view sourceprint?substr('hello word', 3, 2) would return 'll'

substr('hello word', 5) would return 'o word'

substr('hello word', -3, 3) would return 'ord'

substr('hello word', -6, 3) would return 'o w'

substr('hello word', -8, 2) would return 'll'

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'