Need help on case statements to validate records

Question

Hi Experts ,
My table :
seq_num
col2
col3
col4
1
A
12345
P
2
B
1
123%23
3
C
1
23AB
4
D
1
20131001
5
E
1
6
A
13245
Q
7
B
1
12345
8
C
2
1234*AB
9
D
5
20140112
10
E
1
00020
my output
seq_num
col2
col3
col4
Status
Reason
1
A
12345
P
Valid
2
B
1
123%23
invalid
Special Character for col4
3
C
1
23AB
Valid
4
D
1
20131001
Valid
5
E
1
invalid
null for col4
6
A
13245
Q
invalid
Invalid character col4 || invalid number for col3
7
B
1
12345
Valid
8
C
2
1234*AB
Invalid
Special Character col4 ||invalid col3
9
D
5
20140112
invalid
Future dates col4 ||invalid col3
10
E
1
00020
Valid
Sql :
with t as
( select 1 as seq_num,'A' as col2 ,12345 as col3 ,'P' as col4 from dual
union all
select 2 ,'B',1,'123%23' from dual
union all
select 3,'C',1,'23AB' from dual
union all
select 4,'D',1,'21-02-2013' from dual
union all
select 5,'E',1,null from dual
union all
select 6,'A,13245,'Q' from dual
union all
select 7,'B',1,12345 from dual
union all
select 8,'C',2,'1234*AB' from dual
union all
select 9,'D',5,'25-01-2014' from dual
union all
select 10,'E',1,20 from dual
I am applying rules on col3 and col4 for each records row-wise.
I need case statements to populate status and reason columns after applying below rules
Rules
Col3 :
For A record ,it should be 12345 always .
For B,C,D,E , record should be always 1
col4
For A record , it should be either P or R
No null values for all A, B,C,D,E records
for B record , it dont contain special charecters
for C RECORD ,  it dont contain special charecters
for D record ,it should not contain future dates (dates are in yyyymmdd format and  less than  sysdates are valid )
I have other columns as well ,as i not included here
.It would be great if you Could  help on case statements
Thanks and Regards,
Sumanth

Answer 1

I've adjusted Gregs nice example a bit. This should work:
with w_base as (
      select seq_num, col2, col3, col4,
             case when (col2 = 'A'                 AND col3 = 12345 )
                    OR (col2 in ('B','C','D','E')  AND col3 = 1)
                        then '' else '||invalid col3' end ||
             case when (col2 = 'A'        AND col4 not IN ( 'P', 'R' ) )
                        then '||invalid col4' else '' end ||
             case when (col2 IN ( 'B', 'C' )   AND col4 != translate(col4, 'a!@#$%^*()','a') )
                        then '||special character for col4' else '' end ||
             case when (col2 = 'D'        AND col4 >= to_char(sysdate,'yyyymmdd') )
                        then '||future dates col4' else '' end
               reason
      from ( select 1 as seq_num, 'A' as col2, 12345 as col3, 'P' as col4  from dual union all
             select 2,            'B',         1,             '123%23'     from dual union all
             select 3,            'C',         1,             '23AB'       from dual union all
             select 4,            'D',         1,             '20130212'   from dual union all
             select 5,            'E',         1,             null         from dual union all
             select 6,            'A',         13245,         'Q'          from dual union all
             select 7,            'B',         1,             '12345'      from dual union all
             select 8,            'C',         2,             '1234*AB'    from dual union all
             select 9,            'D',         5,             '20140125'   from dual union all
             select 10,           'E',         1,             '20'         from dual )
Select seq_num, col2, col3, col4,
       case when reason is null then 'Valid' else 'Invalid' end status,
       substr(reason, 3 ) reason
from w_base
It returns
SEQ_NUM
COL2
COL3
COL4
STATUS
REASON
1
A
12345
P
Valid
2
B
1
123%23
Invalid
special character for col4
3
C
1
23AB
Valid
4
D
1
20130212
Valid
5
E
1
Valid
6
A
13245
Q
Invalid
invalid col3||invalid col4
7
B
1
12345
Valid
8
C
2
1234*AB
Invalid
invalid col3||special character for col4
9
D
5
20140125
Invalid
invalid col3||future dates col4
10
E
1
20
Valid
edited some bugs :) now it should be fine! really