http://www.techonthenet.com/oracle/functions/substr.php
매번 substr에서 start_position값을 0으로 해야 하는지 1로 해야 하는지 헤갈리게 되는데....
Oracle/PLSQL: SUBSTR Function
In Oracle/PLSQL, the SUBSTR functions allows you to extract a substring from a string.
Syntax
The syntax for the SUBSTR function is:
SUBSTR( string, start_position, [ length ] )
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, the SUBSTR function will return the entire string.
Note
If start_position is 0, then the SUBSTR function treats start_position as 1 (ie: the first position in the string).
If start_position is a positive number, then the SUBSTR function starts from the beginning of the string.
If start_position is a negative number, then the SUBSTR function starts from the end of the string and counts backwards.
If length is a negative number, then the SUBSTR function will return a NULL value.
Applies To
- Oracle 12c, Oracle 11g, Oracle 10g, Oracle 9i, Oracle 8i
For Example
The SUBSTR function can be used in Oracle/PLSQL. 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' |
