Help needed in the a sql query

Question

hi,
i have small but tricky piece of requirements,
following is the input
Id     id_type     id_level     id_name
1     F     A_1     Beta1
2     W     A_1     Beta2
3     W     A_1     Beta3
4     L     A_1     Alpha0
5     W     A_1     Beta4
6     W     A_1     Beta5
now whenever
Id_level = A_1, and id_name = Alpha0 and id_type = L then               
id_level = B_1               
and the coming next 2 levels after this should have id_level C_1
the output should be as follows
Id     id_type     id_level     id_name
1     F     A_1     Beta1
2     W     A_1     Beta2
3     W     A_1     Beta3
4     L     B_1     Alpha0
5     W     C_1     Beta4
6     W     C_1     Beta5
kindly let me know if this could be possible in sql,
if i am missing something here plz highlight it to me,
kindly give me some tips or hints,thanks and regards
nic

Answer 1

SQL> WITH Test_Data AS (
  2    SELECT 1 AS Id, 'F' AS Id_Type, 'A_1' AS Id_Level, 'Beta1' AS Id_Name FROM Dual UNION ALL
  3    SELECT 2,       'W',            'A_1',             'Beta2'            FROM Dual UNION ALL
  4    SELECT 3,       'W',            'A_1',             'Beta3'            FROM Dual UNION ALL
  5    SELECT 6,       'L',            'A_1',             'Alpha0'           FROM Dual UNION ALL
  6    SELECT 8,       'W',            'A_1',             'Beta4'            FROM Dual UNION ALL
  7    SELECT 10,      'W',            'A_1',             'Beta4'            FROM Dual UNION ALL
  8    SELECT 11,      'W',            'A_1',             'Beta5'            FROM Dual
  9  )
10  SELECT Id, Id_Type,
11    CASE WHEN Id_Level = 'A_1' AND Id_Name = 'Alpha0' AND Id_Type = 'L'
12           THEN 'B_1'
13         WHEN COUNT(CASE WHEN Id_Level = 'A_1' AND Id_Name = 'Alpha0' AND Id_Type = 'L' THEN 1 ELSE NULL END)
14                OVER(ORDER BY Id ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) = 0
15           THEN Id_Level
16         WHEN COUNT(CASE WHEN Id_Level = 'A_1' AND Id_Name = 'Alpha0' AND Id_Type = 'L' THEN 1 ELSE NULL END)
17                OVER(ORDER BY Id ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) > 0
18           THEN 'C_1'
19     END AS Id_Level,
20     Id_Name
21  FROM Test_Data
22  ORDER BY Id;
        ID I ID_ ID_NAM
         1 F A_1 Beta1
         2 W A_1 Beta2
         3 W A_1 Beta3
         6 L B_1 Alpha0
         8 W C_1 Beta4
        10 W C_1 Beta4
        11 W C_1 Beta5
7 rows selected.Regards,
Dima