Extract first character of each word in MySQL using a RegEx - mysql

Question

In my MySQL database I have a column of strings in UTF-8 format for which I want to extract the first character using a RegEx, for example.
Assuming a RegEx which ONLY extracts the following characters:
ਹਮਜਰਣਚਕਨਖਲਨ
And given the following string:
ਹੁਕਮਿ ਰਜਾਈ ਚਲਣਾ ਨਾਨਕ ਲਿਖਿਆ ਨਾਲਿ ॥੧॥
The only characters extracted would be:
ਹਰਚਨਲਨ
I know the following steps would be required to solve this problem:
Break the string into individual words (substrings) by using space as the delimiter
For each word extract the first letter (substring of a substring) if it matches what is in the regex of valid characters
I have looked at all the similar questions/answers on SO and none have been able to solve my problem thus far.

Answer 1

I realy don't know MySql Regex Syntax and restrictions(never used), but you can add leading space before string, and match with something simple like this: " ([ਮਜਰਣਚਕਨਖਲਨ]{1})"
So, if you concatenate matched groups you will have this string "ਰਚਨਲਨ"(only "ਹ" not matched, because it's not exists in sample")
in C# it may look like this(working sample):
namespace TestRegex
{
using System.Linq;
using System.Text.RegularExpressions;
using System.Windows.Forms;
class Program
{
static void Main(string[] args)
{
// leading space(to match first word too)
// + sample string
var sample = " ";
sample += "ਹੁਕਮਿ ਰਜਾਈ ਚਲਣਾ ਨਾਨਕ ਲਿਖਿਆ ਨਾਲਿ ॥੧॥";
// Regex pattern that will math space, and
// if next character in set - add it to "match group 1"
var pattern = " ([ਮਜਰਣਚਕਨਖਲਨ]{1})";
// select every "match group 1" from matches as array
var result = from Match m in Regex.Matches(sample, pattern)
select m.Groups[1];
// concatenate array content into one string and
// show it in message box to user, for example..
MessageBox.Show(string.Concat(result));
}
}
}
in most non-query languages it will be look almost same. For example in php you need to do preg_match_all, and in foreach loop add "$match[i][1]"(every "match group 1") from every match to end of one single string.
well.. pretty simple. but not for mysql...

Answer 2

I finally achieved this with the help of a programmer friend of mine. I directly pasted the following piece of code into the SQL section of my database in PhpMyAdmin:
delimiter $$
drop function if exists `initials`$$
CREATE FUNCTION `initials`(str text, expr text) RETURNS text CHARSET utf8
begin
declare result text default '';
declare buffer text default '';
declare i int default 1;
if(str is null) then
return null;
end if;
set buffer = trim(str);
while i <= length(buffer) do
if substr(buffer, i, 1) regexp expr then
set result = concat( result, substr( buffer, i, 1 ));
set i = i + 1;
while i <= length( buffer ) and substr(buffer, i, 1) regexp expr do
set i = i + 1;
end while;
while i <= length( buffer ) and substr(buffer, i, 1) not regexp expr do
set i = i + 1;
end while;
else
set i = i + 1;
end if;
end while;
return result;
end$$
drop function if exists `acronym`$$
CREATE FUNCTION `acronym`(str text) RETURNS text CHARSET utf8
begin
declare result text default '';
set result = initials( str, '[ੴਓੳਅੲਸਹਕਖਗਘਙਚਛਜਝਞਟਠਡਢਣਤਥਦਧਨਪਫਬਭਮਯਰਲਵੜਸ਼ਖ਼ਗ਼ਜ਼ਫ਼ਲ਼]' );
return result;
end$$
delimiter ;
UPDATE scriptures SET search = acronym(scripture)
Just to explain the last line:
scriptures is the table I want to update
search is a new empty column I created inside the table to store the result
scripture is an existing column inside the scriptures table with all the strings I want to extract from
acronym is the function previously declared which is looking to match the first letter of each word with a character from the RegEx [ੴਓੳਅੲਸਹਕਖਗਘਙਚਛਜਝਞਟਠਡਢਣਤਥਦਧਨਪਫਬਭਮਯਰਲਵੜਸ਼ਖ਼ਗ਼ਜ਼ਫ਼ਲ਼]
So this final line of the code will go through each row of the column scripture, apply the function acronym to it and store the result in the new search column.
Perfect! Exactly what I was looking for :)