Обсуждение: how can I replace all instances of a pattern

On Tue, Mar 26, 2013 at 09:13:39AM -0400, James Sharrett wrote:
> Sorry, caught a typo.  Mytext1 is correctly replaced because only one
> instance of the character (space) is in the string.
> 
> This deals with the correct characters but only does the first instance of
> the character so the output is:
> 
>     'Mytext1'
>     'Mytext 2'  (wrong)
>     'Mytext-3'  (wrong)
>     'My_text4'
>     'My!text5'
> 

Hi James,

Try adding the g flag to the regex (for global). From the documentation:

regexp_replace('foobarbaz', 'b..', 'X')                                  fooXbaz
regexp_replace('foobarbaz', 'b..', 'X', 'g')                                  fooXX
regexp_replace('foobarbaz', 'b(..)', E'X\\1Y', 'g')                                  fooXarYXazY

Regards,
Ken

I'm trying remove all instances of non-alphanumeric or underscore characters from a query result for further use.  This is part of a function I'm writing that is in plpgsql

Examples:

  Original value

    'My text1'

    'My text 2'

    'My-text-3'

    'My_text4'

    'My!text5'

   Desired

    'Mytext1'

    'Mytext2'

    'Mytext3'

    'My_text4'  (no change)

    'Mytext5'

The field containing the text is column_name.  I tried the following:

  Select regexp_replace(column_name,'\W','') from mytable

This deals with the correct characters but only does the first instance of the character so the output is:

    'My text1'

    'Mytext 2'  (wrong)

    'Mytext-3'  (wrong)

    'My_text4'

    'My!text5'

I managed to get the desired output by writing the text into a variable through a loop and then just keep looping on the variable until all the characters are removed:

sql_qry:= 'select column_name from mytable';

for sql_record in execute sql_qry loop

curr_record := sql_record.column_name;

        while length(substring(curr_record from '\W'))>0 loop

            curr_record := regexp_replace(curr_record, '\W','');

        end loop;

…. rest of the code

This works but it seems like a lot of work to do something this simple but I cannot find any function that will replace all instances of a string AND can base it on a regular expression pattern.  Is there a better way to do this in 9.1?

Thanks Ken!  I missed that option going through the documentation.

>