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How to Write "Trim" Function In Postgresql?

5 minutes read

To write a "trim" function in PostgreSQL, you can use the following syntax:


CREATE OR REPLACE FUNCTION trim_chars(TEXT, TEXT) RETURNS TEXT AS $$ SELECT btrim($1, $2); $$ LANGUAGE SQL;


This function takes two arguments: the first argument is the text to be trimmed, and the second argument is the characters to trim from the text. The function then uses the built-in "btrim" function in PostgreSQL to remove any leading or trailing instances of the specified characters from the input text.


You can then call this function in your queries to trim text as needed.


What is the effect of using the "trim" function with single quotes in PostgreSQL?

In PostgreSQL, the trim function is used to remove specified characters (usually whitespace) from the beginning and end of a string. When using the trim function with single quotes, it will remove any single quotes that appear at the beginning and end of the string.


For example, if you have a string 'Hello' and you use the trim function with single quotes like this: trim('''Hello''', ''''), the output will be Hello (without the single quotes).


In general, using the trim function with single quotes can be useful when you want to remove surrounding single quotes from a string.


How to write a custom "trim" function in PostgreSQL?

To write a custom "trim" function in PostgreSQL, you can create a new function that takes in a string as input and removes any leading and trailing spaces from it. Here is an example of how you can create a custom "trim" function in PostgreSQL:

  1. First, connect to your PostgreSQL database and open a new query window.
  2. Create a new function with the following code: 
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CREATE OR REPLACE FUNCTION custom_trim(input_string text) RETURNS text AS $$
BEGIN
  RETURN regexp_replace(input_string, '^\s+|\s+$', '', 'g');
END;
$$ LANGUAGE plpgsql;


  1. This function uses the regexp_replace function to remove any leading (^\s+) and trailing (\s+$) spaces from the input string. It then returns the trimmed string.
  2. You can now use the custom "trim" function in your queries like any other function. For example: 
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SELECT custom_trim('   Hello World   ');


This will return 'Hello World' with the leading and trailing spaces removed.


That's it! You have now created a custom "trim" function in PostgreSQL.


How to trim specific characters using a custom function in PostgreSQL?

To trim specific characters using a custom function in PostgreSQL, you can create a user-defined function that utilizes the REPLACE function in PostgreSQL. Here's an example of how you can create a custom function to trim specific characters:

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CREATE OR REPLACE FUNCTION trim_specific_chars(input_text text, chars_to_trim text)
RETURNS text AS
$$
BEGIN
  RETURN REPLACE(input_text, chars_to_trim, '');
END
$$
LANGUAGE plpgsql;


In the above function, input_text is the text that you want to trim specific characters from, and chars_to_trim is the specific characters that you want to remove from the input text. The function uses the REPLACE function to replace all occurrences of the specified characters with an empty string, effectively trimming them from the input text.


You can then use this custom function to trim specific characters from a text column in a table like this:

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SELECT trim_specific_chars('abc123def456ghi', '123456');


This will return the text 'abcdefghi' after trimming the specified characters '123456' from the input text 'abc123def456ghi'.


What is the syntax for the "trim" function in PostgreSQL?

The syntax for the "trim" function in PostgreSQL is as follows:

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TRIM([LEADING | TRAILING | BOTH] [characters FROM] string)


Where:

  • LEADING trims characters only from the start of the string.
  • TRAILING trims characters only from the end of the string.
  • BOTH trims characters from both the start and end of the string.
  • characters specifies the characters that should be trimmed from the string.
  • string is the input string that you want to trim.


Example:

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SELECT TRIM('  hello  ');


This will return 'hello'.


How to trim whitespace from both ends of a string using the "trim" function in PostgreSQL?

To trim whitespace from both ends of a string in PostgreSQL, you can use the TRIM function. Here is an example of how to use the TRIM function to trim whitespace from both ends of a string:

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SELECT TRIM('   Hello, World   ');


This query will return the string "Hello, World" with the leading and trailing whitespaces removed.


You can also specify the specific characters you want to trim by providing them as an additional parameter to the TRIM function. For example, to trim both leading and trailing commas from a string, you can use the following query:

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SELECT TRIM(',' FROM '  ,Hello, World, ');


This query will return the string "Hello, World" with the leading and trailing commas removed.


Additionally, you can specify whether you want to trim only leading whitespaces (LEADING), only trailing whitespaces (TRAILING), or both leading and trailing whitespaces (BOTH). Here is an example of how to trim only leading whitespaces:

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SELECT TRIM(LEADING ' ' FROM '   Hello, World');


This query will return the string "Hello, World" with only the leading whitespaces removed.


How to trim multiple characters from a string using the "trim" function in PostgreSQL?

To trim multiple characters from a string using the "trim" function in PostgreSQL, you can specify the characters you want to remove as the second argument of the function. Here's the syntax:

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TRIM( [ leading_trailing_both from ] string text [, characters text ])


For example, if you want to trim both the characters 'a' and 'b' from the beginning and end of a string, you can use the following query:

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SELECT TRIM('abcbdefcba' FROM 'abcdefgh') AS trimmed_string;


This will return 'def' as the result, as 'a' and 'b' characters at the start and end are removed.


You can also use the "BOTH" keyword to specify that the characters should be trimmed from both the beginning and end of the string:

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SELECT TRIM(BOTH 'ab' FROM 'abcbdefcba') AS trimmed_string;


This will also return 'cdefc' as the result, as 'a' and 'b' characters at the start and end are removed.


Remember that the TRIM function is case-sensitive, so 'A' and 'B' are considered different characters from 'a' and 'b'.

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