CREATE TYPE Categories AS OBJECT(  
priority VARCHAR2(10),  
subcategory VARCHAR2(60)  
); 

CREATE TYPE CategoriesList AS TABLE OF Categories; 

CREATE TABLE projekt (  
projektname VARCHAR2(10),  
categories CategoriesList)  
NESTED TABLE categories STORE AS categories_tab

INSERT INTO projekt VALUES('a',CategoriesList(Categories('1','subcat1'),  
                                              Categories('2','subcat4'),  
                                              Categories('3','subcat5')))

INSERT INTO projekt VALUES('b',CategoriesList(Categories('1','subcat1'),  
                                              Categories('2','subcat3'),  
                                              Categories('3','subcat5')))

INSERT INTO projekt VALUES('c',CategoriesList(Categories('1','subcat1'),  
                                              Categories('2','subcat2')))

select * from projekt

select t.* 
from   projekt p, 
       table (p.categories) t