Aggregate Strings

To create a comma separated string of values in columns from different rows in an Oracle table...

with emp as
(select name
 from (select 'Motorman' name from dual
       union
       select 'Captain' from dual
       union
       select 'Wilma' from dual
       )
order by name
)
select ltrim(extract(XMLAgg(XMLElement ("NAME" ,','||name)) ,'NAME/text()') ,',') name_csv
 from emp

Result will be
Captain,Motorman,Wilma

and the reverse....

select column_value name
  from table (sys.odcivarchar2list ('Captain' ,'Motorman' ,'Wilma'))

returns

Name
Captain
Motorman
Wilma