I have chosen to ask this question via an example as I think it most clearly illustrates what I am trying to do.
Say I have the following table:
mem
I know it's bad form answering your own question but I have found this useful page:
https://www.ibm.com/developerworks/mydeveloperworks/blogs/SQLTips4DB2LUW/entry/aggregating_strings42?lang=en
Modifying the code there gives:
create table test (member int, number int, time_stamp time)`;
insert into test values
(1,2,'19:21'),
(1,4,'19:24'),
(1,27,'19:37'),
(2,4,'19:01'),
(2,7,'21:56'),
(2,8,'22:00'),
(2,21,'22:01');
select
member, substr(xmlcast(xmlgroup('.' || number as a order by time_stamp) as varchar(60)), 2)
from test
group by member