#  TRIM, LTRIM, RTRIM : Trim String
__*TRIM function*__
__*LTRIM function*__
__*RTRIM function*__
__*ORACLE SQL mode schema*__
+ `TRIM([BOTH|LEADING|TRAILING [substring] FROM] string)`   
  + Returns the string after all**substring** have been removed
  + If **BOTH, LEADING, TRAILING** option is not specified, the default is**BOTH**
  + Spaces will be removed if the**substring** is omitted
+ `LTRIM(), RTRIM(), TRIM()`: You can remove space characters that appear on the left, right, or both sides
+ For example:
  + `SELECT trim(leading 'Ti' from 'TiDB'), ltrim(' TiDB'),'#'||trim(' TiKV ')||'#';`  
```
tidb> ~!@SET @@sql_mode=ORACLE@!~;
Query OK, 0 rows affected (0.00 sec)
tidb> SELECT trim(leading 'Ti' from 'TiDB'), ltrim(' TiDB'),'#'||trim(' TiKV  ')||'#';
+--------------------------------+----------------+---------------------------+
| trim(leading 'Ti' from 'TiDB') | ltrim(' TiDB') | '#'||trim(' TiKV  ')||'#' |
+--------------------------------+----------------+---------------------------+
| DB                             | TiDB           | #TiKV#                    |
+--------------------------------+----------------+---------------------------+
1 row in set (0.00 sec)
```

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The ORACLE SQL mode is a compound pattern that implies pipes_as_concat.

- TRIM () removes prefix and suffix spaces
- LTRIM () removes prefix spaces
- RTRIM () removes suffix spaces