Converting N Rows into 1 Rown N Columns

The below example gives you an idea on how to Convert N rows of data into 1 row N Column. 
The busniess requirement says, "Pull out the list of application users and the corresponding groups they belongs".

Assume each users belongs to 4 to 5 different groups.  The output contains only one record for each row. The output format is something linke this. 

1. username| user_group1| user_group2| user_group3 |user_group4 |user_group5  
2. --------|------------|------------|-------------|------------|------------  
3.         |            |            |             |            |   

user details are stored in adm_users and the group/role details are stored in adm_user_groups. These two tables need to be joined. The query is given below. 

1. SELECT  usr.usr_username ,  
2. MAX(CASE WHEN RN=1 THEN gr_role_name ELSE NULL END)    group1,  
3. MAX(CASE WHEN RN=2 THEN gr_role_name ELSE NULL END)    group2,  
4. MAX(CASE WHEN RN=3 THEN gr_role_name ELSE NULL END)    group3,  
5. MAX(CASE WHEN RN=4 THEN gr_role_name ELSE NULL END)    group4,  
6. MAX(CASE WHEN RN=5 THEN gr_role_name ELSE NULL END)    group5,  
7. FROM (  
8. SELECT  usr.usr_username,grp.gr_role_name,  
9. ROW_NUMBER() OVER (PARTITION BY gr_role_name ORDER BY gr_role_name) AS rn FROM adm_users usr, adm_user_groups grp   
10. WHERE  user.usr_username=grp.grp_usr_username  
11. )  
12. WHERE RN<=5  
13. GROUP BY usr_username;  
14.   
15. Output  
16. --------  
17.   
18. username| user_group1| user_group2| user_group3 |user_group4 |user_group5  
19. --------|------------|------------|-------------|------------|------------  
20. scott   |admin       |developer   |billing      |approver    |  
21. tom     |admin       |developer   |billing      |accounting  | Others