#  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