substr
description
Syntax
VARCHAR substr(VARCHAR content, INT start, INT length)
求子字符串，返回第一个参数描述的字符串中从start开始长度为len的部分字符串。首字母的下标为1。
example
mysql> select substr("Hello doris", 2, 1);
+-----------------------------+
| substr('Hello doris', 2, 1) |
+-----------------------------+
| e |
+-----------------------------+
mysql> select substr("Hello doris", 1, 2);
+-----------------------------+
| substr('Hello doris', 1, 2) |
+-----------------------------+
| He |
+-----------------------------+keywords
SUBSTR