How to remove characters in oracle

How to remove characters in Oracle?

When performing database operations in Oracle, we often need to process text fields, and inevitably we will encounter situations where certain characters need to be removed. So, how do we remove characters in Oracle?

1. Oracle built-in function TRIM

Oracle provides a built-in function TRIM, which is used to remove leading and trailing spaces or specified characters from a string. The syntax is as follows:

TRIM([TRIM_CHARACTER FROM] string)

Among them, string is the string to be processed, TRIM_CHARACTER represents the character to be removed, which can be omitted. By default, the before and after are removed. Space. If you need to remove specified characters, you need to specify the characters to be removed in the TRIM_CHARACTER parameter position. For example:

SELECT TRIM(' ABC ') FROM DUAL; --Remove leading and trailing spaces
--The result is 'ABC'

SELECT TRIM('$' FROM '$123$' ) FROM DUAL; --Remove the specified characters
--The result is '123'

It should be noted that the TRIM function will only remove the characters before and after the string or the specified characters, and will not remove the middle ones. character.

2. Oracle built-in function REPLACE

If you need to remove characters in the middle of a string, you can use the REPLACE function provided by Oracle. The syntax is as follows:

REPLACE(string, old_string, new_string)

Among them, string is the string to be processed, old_string is the character to be replaced, and new_string is the character used to replace old_string. . If new_string is empty, it means that old_string is removed. For example:

SELECT REPLACE('ABCDEF', 'C', '') FROM DUAL;
--The result is 'ABDEF'

3. Oracle regular expression function REGEXP_REPLACE

In some cases, the characters we need to remove do not have fixed characteristics. In this case, we can use the regular expression function REGEXP_REPLACE provided by Oracle. The syntax is as follows:

REGEXP_REPLACE(string, pattern, replacement)

Among them, string is the string to be processed, pattern is a regular expression, used to match the characters to be removed, and replacement is the character used to replace the matched character. For example:

SELECT REGEXP_REPLACE('A123 B456 C789', '[A-Z]', '') FROM DUAL;
--The result is '123 456 789'

The above three The methods are very practical. In Oracle, you can use these built-in functions to quickly process text data, remove useless characters or replace specified characters. Hope this article is helpful to you.

The above is the detailed content of How to remove characters in oracle. For more information, please follow other related articles on the PHP Chinese website!