# `LEFT`, `RIGHT`, `LPAD`, `RPAD`

__*LEFT 函数*__
__*RIGHT 函数*__
__*LPAD 函数*__
__*RPAD 函数*__

+ `LEFT(str, numchar), RIGHT(str, numchar)`: 返回字符串中最左边或最右边的 **numchar** 字符
+ `LPAD(str, len, padstr), RPAD(str, len, padstr)`: 返回一个在左侧或右侧填充有 **padstr** 的字符串,长度不超过 **len** 个字符
+ 例如:
  + `SELECT left('TSO',1), right('TSO',2), lpad('TSO',4,'#'), rpad('TSO',4,'#');` 
```10
tidb> SELECT left('TSO',1), right('TSO',2), lpad('TSO',4,'#'), rpad('TSO',4,'#');
+---------------+----------------+-------------------+-------------------+
| LEFT('TSO',1) | RIGHT('TSO',2) | LPAD('TSO',4,'#') | RPAD('TSO',4,'#') |
+---------------+----------------+-------------------+-------------------+
| T             | SO             | #TSO              | TSO#              |
+---------------+----------------+-------------------+-------------------+
```
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- LEFT()	返回最左侧指定长度的字符
- RIGHT()	返回指定数量的最右侧的字符
- LPAD()	返回字符串参数,左侧添加指定字符串
- RPAD()	以指定次数添加字符串