If I have a simple query like:

OPEN cursor FOR 
SELECT USER_ID FROM USER_TABLE WHERE USER_ID = V_SOME_USER;

this will return records in different rows but how can I return the rows in the following format:

'userid1', 'userid2', 'userid3'.....'useridN'

I want to do this because I want to send this off as a parameter to another stored procedure...Also, what is the limit on how big the string can be when passed to the SP as parameter