DEMO, Oracle - rextester

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--Oracle 11g Express Edition
--please drop objects you've created at the end of the script 
--or check for their existance before creating
--'\\' is a delimiter

drop table table1\\

create table table1( 
Id int,
num varchar(10),
prod varchar(10)
)\\

insert into table1 values(101,'1701A001','book')\\ 
insert into table1 values(102,'1701A001','data')\\ 
insert into table1 values(103,'1702B005','bat')\\
insert into table1 values(104,'1702B005','ball')\\ 
insert into table1 values(105,'1703C006','Stumps')\\

SELECT t2.id,
       t2.num,
       t1.prod
FROM
  (SELECT num,
          listagg(prod, ',') within group(
                                          ORDER BY prod) AS prod
   FROM table1
   GROUP BY num ) t1
JOIN table1 t2 ON t1.num = t2.num
order by t2.id\\

WITH t1 AS
  (SELECT num,
          listagg(prod, ',') within group(
                                          ORDER BY prod) AS prod
   FROM table1
   GROUP BY num)
SELECT t2.id,
       t2.num,
       t1.prod
FROM t1
JOIN table1 t2 ON t1.num = t2.num
ORDER BY t2.id\\


absolute service time: 1,31 sec