TRIM()：从字符串中删除不必要的前导和后缀字符

TRIM()、LTRIM()、RTRIM()

1、TRIM()：从字符串中删除前导和后缀字符

TRIM()：从字符串中删除不必要的前导和后缀字符

语法：
TRIM([{BOTH|LEADING|TRAILING} [removed_str]] FROM str);

-- BOTH:删除前缀和后缀，默认是BOTH
-- LEADING：删除前缀
-- TRAILING：删除后缀
-- removed_str：删除指定字符串，默认是空格


例子：
-- 从字符串中除去前导和尾随空格
mysql> SELECT TRIM(' MySQL TRIM Function ');
+-------------------------------+
| TRIM(' MySQL TRIM Function ') |
+-------------------------------+
| MySQL TRIM Function           |
+-------------------------------+
1 row in set

-- 仅删除前导空格 -
mysql> SELECT TRIM(LEADING FROM '    MySQL TRIM Function   ');
+-------------------------------------------------+
| TRIM(LEADING FROM '    MySQL TRIM Function   ') |
+-------------------------------------------------+
| MySQL TRIM Function                             |
+-------------------------------------------------+
1 row in set

-- 仅删除尾随空格 -
mysql> SELECT TRIM(TRAILING FROM '    MySQL TRIM Function   ');
+--------------------------------------------------+
| TRIM(TRAILING FROM '    MySQL TRIM Function   ') |
+--------------------------------------------------+
|     MySQL TRIM Function                          |
+--------------------------------------------------+
1 row in set


-- 删除指定字符
mysql> SELECT TRIM('abc' FROM 'abc MySQL TRIM Function abc');
+--------------------------------------------------+
| TRIM('abc' FROM 'abc MySQL TRIM Function abc')   |
+--------------------------------------------------+
| MySQL TRIM Function                              |
+--------------------------------------------------+
1 row in set

2、LTRIM()

LTRIM()：删除字符串的前缀空格

例子：
mysql> SELECT LTRIM('  MySQL LTRIM function  ');
-- 结果：'MySQL LTRIM function  '

3、RTRIM()

RTRIM()：删除字符串的后缀空格

例子：
mysql> SELECT RTRIM('  MySQL LTRIM function  ');
-- 结果：'  MySQL LTRIM function'