SubQuery returning Multiple rows - sql

Question

I have got Two Tables
Product (Id, Name, CCode)
Category (CCode, CatName) - No Primary Key
Insert Into ProductNew (DW_Prod_Id, ProdId, ProdName, CC, CName)
Select Dw_Prod_Id.Nextval, Id, Name, CCode,
(Select CatName
From Category cc, Product p
Where cc.CCode IN p.CatCode
Group By CatName )
From Product;
SQL Error: ORA-01427: single-row subquery returns more than one row
01427. 00000 - "single-row subquery returns more than one row"
I am getting the above error Because my SubQuery returns more than one row.
I would like to Match the CatCode of each row from Product table to the Category Table so that I can obtain the CatName and then Insert rows into my New Table :)

Answer 1

if product can have only one category :
INSERT INTO ProdcutNew (DW_Prod_Id, ProdId, ProdName, CC, CName)
(SELECT Dw_Prod_Id.Nextval, p.Id, p.Name, cc.CCode, cc.CName
FROM Product p
INNER JOIN Category cc on p.CatCode = cc.CCode)
And you can correct your table name
ProdcutNew
to ProductNew ;)
EDIT :
But if, as #Gordon Linoff pointed, you have duplicates CCode, this won't work.
If you don't want a primary key on Category table, add at least a unique constraint (you'll have to clean your datas first)
ALTER TABLE Category ADD CONSTRAINT Unique_code UNIQUE(CCode);
EDIT 2 :
But the proper way would be :
Add an Id in Category as PK, and use it as Category_ID FK in Product (if CCode can change)
With the unique constraint on CCode.

Answer 2

You appear to have dulicates in your category table; otherwise a simple join would suffice:
select p.*, c.ccode
from Category c join
Product p
on c.ccode = p.catcode
To choose one category arbitrarily, do something like:
select p.*, c.ccode
from (select c.*
from (select c.*, row_number() over (partition by c.ccode order by c.ccode) as seqnum
from Category c
) c
where seqnum = 1
) c join
Product p
on c.ccode = p.catcode