I have one table with the following kinds of records in it. I have Salesman
and associated account numbers (comma separated).
+----------+----------
I assume that you need this just as a one-off operation in order to restructure your schema into something usable.
Do you have another table which lists all the possible account numbers? If you do then you can do this:
SELECT salesman, a.Acct
FROM account AS a
JOIN salesman_account AS sa
ON FIND_IN_SET(a.Acct, sa.Acct)