substring_index

substring_index

description

Syntax

VARCHAR substring_index(VARCHAR content, VARCHAR delimiter, INT field)

返回 content 的子字符串，在 delimiter 出现 field 次的位置按如下规则截取：
如果 field > 0，则从左边算起，返回截取位置前的子串；
如果 field < 0，则从右边算起，返回截取位置后的子串； 如果 field = 0，返回一个空串（content 不为null）, 或者Null （content = null）。

example

mysql> select substring_index("hello world", " ", 1);
+----------------------------------------+
| substring_index("hello world", " ", 1) |
+----------------------------------------+
| hello                                  |
+----------------------------------------+
mysql> select substring_index("hello world", " ", 2);
+----------------------------------------+
| substring_index("hello world", " ", 2) |
+----------------------------------------+
| hello world                            |
+----------------------------------------+
mysql> select substring_index("hello world", " ", -1);
+-----------------------------------------+
| substring_index("hello world", " ", -1) |
+-----------------------------------------+
| world                                   |
+-----------------------------------------+
mysql> select substring_index("hello world", " ", -2);
+-----------------------------------------+
| substring_index("hello world", " ", -2) |
+-----------------------------------------+
| hello world                             |
+-----------------------------------------+
mysql> select substring_index("hello world", " ", -3);
+-----------------------------------------+
| substring_index("hello world", " ", -3) |
+-----------------------------------------+
| hello world                             |
+-----------------------------------------+
mysql> select substring_index("hello world", " ", 0);
+----------------------------------------+
| substring_index("hello world", " ", 0) |
+----------------------------------------+
|                                        |
+----------------------------------------+