Column values into one delimited field

[Francesco Facco de Lagarda]

Hello all,
i'm trying to implement change management on a number of tables (who changes what when). I was thinking of doing it using triggers ON BEFORE INSERT, UPDATE, and DELETE ad writing to a changes table to have the following schema
uID - Unique Id of record
userId - id of user making change
timeStamp - timestamp of change
tableName - name of table being modified (i.e. friends)
Operation - operation : INSERT/UPDATE/DELTE
FieldList - table fieldList, eg friendID, firstName, lastName, email
ValuesBefore 1,'John','Sliver','[e-mail]'
ValuesAfter 1,'John','Sterling Silver', '[e-mail]'

I can probably get a delimited fieldName list from:

SELECT GROUP_CONCAT(COLUMN_NAME) cols
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = 'myDb'
AND TABLE_NAME = 'friends'
ORDER BY ORDINAL_POSITION

but my question is HOW to get the value lists (for the before and after records)?