TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str)

TRIM([remstr FROM] str)

返回字符串str，删除了所有使用Remstar前缀或后缀。如果没有说明符BOTH，LEADING，或TRAILING给出，BOTH是假定(默认)的。Remstar是可选的，如果未指定，空格被删除。

SQL> SELECT TRIM('  bar   ');
+---------------------------------------------------------+
| TRIM('  bar   ')                                        |
+---------------------------------------------------------+
| bar                                                     |
+---------------------------------------------------------+
1 row in set (0.00 sec)

SQL> SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx');
+---------------------------------------------------------+
| TRIM(LEADING 'x' FROM 'xxxbarxxx')                      |
+---------------------------------------------------------+
| barxxx                                                  |
+---------------------------------------------------------+
1 row in set (0.00 sec)

SQL> SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx');
+---------------------------------------------------------+
| TRIM(BOTH 'x' FROM 'xxxbarxxx')                         |
+---------------------------------------------------------+
| bar                                                     |
+---------------------------------------------------------+
1 row in set (0.00 sec)

SQL> SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz');
+---------------------------------------------------------+
| TRIM(TRAILING 'xyz' FROM 'barxxyz')                     |
+---------------------------------------------------------+
| barx                                                    |
+---------------------------------------------------------+
1 row in set (0.00 sec)