Format rows into comma seperated string

Example 

select userid,company_name,remarks from visit_details where userid=786;

    USERID COMPANY_NAME                   REMARKS
---------- ------------------------------ ---------------------------------------
       786 abc                            xyz
       786 def                            uvw
       786 ghi                            pqr

The output requirement is 

       786 abc,def,ghi                    xyz,uvw,pqr


Solution

 select userid,
       (
       select listagg(company_name,',')  within group (order by company_name) 
       from visit_details where userid=786
       ) as company_name,      
       (
       select listagg(remarks,',')  within group (order by remarks) 
       from visit_details where userid=786
       ) as remarks
       from
       (
         select userid,collect(distinct company_name),collect(distinct remarks)
         from visit_details where userid=786 group by userid
         )  ;


 
    USERID COMPANY_NAME                   REMARKS
---------- ------------------------------ ---------------------------------------
       786 abc,def,ghi                    xyz,uvw,pqr


2)  On single column

select listagg(company_name,',')  within group (order by company_name) 
       from visit_details where userid=786  ;



COMPANY_NAME              
----------
abc,def,ghi