[SQL] how can I replace all instances of a pattern

[James Sharrett]

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;

Š. 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?