大家都知道trim函数是用来清除字符串的空格的.今天却发现它有新用途.

1,清除首尾空格:

SQL> select length(trim('    hello   ')) from dual;

LENGTH(TRIM('HELLO'))
---------------------
                    5

等同于

SQL> select length(trim(both from '    hello   ')) from dual;

LENGTH(TRIM('HELLO'))
---------------------
                    5

2,清除左边空格

SQL> select length(trim(leading from '    hello   ')) from dual;

LENGTH(TRIM(LEADINGFROM'HE
--------------------------
                         8

等同于ltrim

3,清除右边空格

SQL> select length(trim(trailing from '    hello   ')) from dual;

LENGTH(TRIM(TRAILINGFROM'H
--------------------------
                         9

等同于rtrim

3,清除某个字符(注意是某个字符不是字符串)

SQL> select length(trim(leading 'x' from 'xxxxhelloxxxxx')) from dual;

LENGTH(TRIM(LEADING'X'FROM'XXX
------------------------------
                            10

SQL> select length(trim(trailing 'x' from 'xxxxhelloxxxxx')) from dual;

LENGTH(TRIM(TRAILING'X'FROM'XX
------------------------------
                             9

另:清除某个字符串可以用ltrim和rtrim函数办到.
SQL> select length(rtrim('xyxyhelloyxyxx','xy')) from dual;

LENGTH(RTRIM('XYXYHELLOYXYXX',
------------------------------
                             9

SQL> select rtrim('xyxyhelloyxyxx','xy') from dual;

RTRIM('XYXYHELLOYXYXX','XY')
--------------------------------
xyxyhello

SQL> select ltrim('xyxyhelloyxyxx','xy') from dual;

LTRIM('XYXYHELLOYXYXX','XY')
--------------------------------
helloyxyxx

共同学习~~~~~