| --- |
| { |
| "title": "SUBSTRING", |
| "language": "en" |
| } |
| --- |
| |
| ## substring |
| ### description |
| #### Syntax |
| |
| `VARCHAR substring(VARCHAR str, INT pos[, INT len])` |
| |
| The forms without a `len` argument return a substring from string `str` starting at position `pos`. |
| The forms with a `len` argument return a substring len characters long from string `str`, starting at position pos. |
| It is also possible to use a negative value for `pos`. In this case, |
| the beginning of the substring is `pos` characters from the end of the string, rather than the beginning. |
| A negative value may be used for `pos` in any of the forms of this function. |
| A value of 0 for `pos` returns an empty string. |
| |
| For all forms of SUBSTRING(), |
| the position of the first character in the string from which the substring is to be extracted is reckoned as 1. |
| |
| If len is less than 1, the result is the empty string. |
| |
| ### example |
| |
| ``` |
| mysql> select substring('abc1', 2); |
| +-----------------------------+ |
| | substring('abc1', 2) | |
| +-----------------------------+ |
| | bc1 | |
| +-----------------------------+ |
| |
| mysql> select substring('abc1', -2); |
| +-----------------------------+ |
| | substring('abc1', -2) | |
| +-----------------------------+ |
| | c1 | |
| +-----------------------------+ |
| |
| mysql> select substring('abc1', 0); |
| +----------------------+ |
| | substring('abc1', 0) | |
| +----------------------+ |
| | | |
| +----------------------+ |
| |
| mysql> select substring('abc1', 5); |
| +-----------------------------+ |
| | substring('abc1', 5) | |
| +-----------------------------+ |
| | NULL | |
| +-----------------------------+ |
| |
| mysql> select substring('abc1def', 2, 2); |
| +-----------------------------+ |
| | substring('abc1def', 2, 2) | |
| +-----------------------------+ |
| | bc | |
| +-----------------------------+ |
| ``` |
| |
| ### keywords |
| SUBSTRING, STRING |