Usage of trim, ltrim and rtrim functions of Oracle

Basic usage ：

1. Remove spaces before and after the specified string

select trim(' hello caicai ')trim from dual;-- When no alias is added , There is still a space to the right of the display string .

  

2. Remove the space around the specified string

select ltrim(' hello caicai ')ltrim from dual;-- Left

select rtrim(' hello caicai ')rtrim from dual;-- Right

Advanced usage ：

Receive other parameters to remove the left of the specified string 、 Characters on the right and both sides .

The advanced usage here can not only remove half width spaces , You can also remove all blank spaces , And basic trim Usage: only half width spaces can be removed .

1. The case where the interception set is one character （ Be careful ： The intercept set here can only be one character , Otherwise, the report will be wrong ）

select trim(leading  ' '  from  '   hello caicai  ') leadingtrim from dual;

select trim(trailing  ' '  from  '   hello caicai  ') trailingtrim from dual;

select trim(both ' '  from  '   hello caicai  ') bothtrim from dual;

select trim(leading  'y'  from  'ya   hello caicai  y') leadingtrim from dual;

select trim(trailing  'y'  from  'ya   hello caicai y') trailingtrim from dual;

select trim(both 'y'  from  'ya   hello caicai y') bothtrim from dual;

No keywords leading,trailing,both, Its usage is equivalent to trim Basic usage .

select trim( 'y'  from  'ya   hello caicai  y') leadingtrim from dual;

2. When the interception set is multiple characters ：

ltrim(string1,string2),rtrim(string1,string2)

ltrim(string1,string2)： From a string string1 The left side starts to remove and string2 A character that matches a single character in a character set , Until string1 Encountered a character in , The character is not in string2 In the character set .

In a nutshell , take string2 Each character in the is associated with string1 Each character starting on the left matches , If the same , Then continue to match , If it is different, return its characters and the remaining characters .

select ltrim('abcbcaxcba','abc') ltrim from dual;

rtrim(string1,string2)： From a string string1 The right side starts to remove and string2 A character that matches a single character in a character set , Until string1 Encountered a character in , The character is not in string2 In the character set .

In a nutshell , take string2 Each character in the is associated with string1 Each character starting on the right matches , If the same , Then continue to match , If it is different, return its characters and the remaining characters .

select rtrim('abcbcaxcba','abc') rtrim from dual;

Be careful ：

In the use of trim,ltrim,rtrim Advanced use of , The blank space corresponds to Airbus , Empty string corresponds to empty string , Otherwise, you will not get the results you want . Note spaces and empty strings , Space refers to a space in quotation marks , An empty string means that there is nothing between the quotation marks .

Such as ：

                        Space               Empty string

SELECT ltrim('  abcbcaxcba','') rtrim FROM dual;

                         Space             Space

SELECT ltrim('  abcbcaxcba',' ') rtrim FROM dual;

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