CASE statement, maybe

Question

I am querying three tables,A,B,C to create a view,V. There must be a comparison of three columns,A.col_1,B.col_1,B.col_2 to determine a third column's entry,V.col.The third column does not reside in any of the tables, only in the view.
Select pl.class
from criminal pl,mental mh
where mh.statute_subsec=pl.statue_subsec
CASE MAX_TERM
If pl.class like 'A%' then 'life'
If pl.class like 'B' then '25'
If pl.class like 'C' then '15'
If pl.class like 'D' then '7'
If pl.class like 'E' then '4'
end;
This is more like the logic flowchart than the code but this is what I want to achieve..
Once pl.class(B.col_2) has been determined by comparing the other two columns, MAX_TERM (V.col)is determined similar to the CASE statement above.
This must somehow be included in a larger select query with other columns to create one view,V.

Answer 1

I guess you are looking for something like this:
SQL> SELECT dname,
  2         ename,
  3         CASE
  4             WHEN pl.class LIKE 'N%' THEN
  5              'life'
  6             WHEN pl.class LIKE 'D%' THEN
  7              '25'
  8             WHEN pl.class LIKE 'O%' THEN
  9              '15'
10             WHEN pl.class LIKE 'D' THEN
11              '7'
12             WHEN pl.class LIKE 'E' THEN
13              '4'
14         END
15  FROM   (SELECT d.dname,
16                 e.ename,
17                 DECODE(d.deptno,
18                        10,
19                        'New York',
20                        20,
21                        'Dallas',
22                        'Others') class
23          FROM   scott.dept d,
24                 scott.emp  e
25          WHERE  d.deptno = e.deptno) pl ;
DNAME          ENAME      CASE
accounting     clark      life
accounting     king       life
accounting     miller     life
research       smith      25
research       jones      25
research       scott      25
research       adams      25
research       ford       25
sales          allen      15
sales          ward       15
sales          martin     15
sales          blake      15
sales          turner     15
sales          james      15
14 rows selected.
SQL>