Updating multiple fields ... need an advice.

Question

Hello all,
I have a bit of a trouble with updating multiple fields in one table...
Lets say we have two tables. Table one is called t_employe for example:
create table t_employe (
year number,
line varchar2(1),
counter number,
value number)Lets set some random data into table:
insert all
into t_employe (year, line,counter, value)
values(2011,'3','2946','3344')
into t_employe (year, line,counter, value)
values(2011,'3','2947','4433')
into t_employe (year, line,counter, value)
values(2011,'3','2948','4455')
into t_employe (year, line,counter, value)
values(2011,'3','2949','5544')
select * from dualOk second table would be:
create table to_update (
year number,
line varchar2(1),
counter number,
date_pos_1 date,
value_pos_1 number,
date_pos_2 date,
value_pos_2 number,
date_pos_3 date,
value_pos_3 number,
date_pos_4 date,
value_pos_4 number,
date_pos_5 date,
value_pos_5 number)Data:
insert all
into to_update (year, line,counter, date_pos_1,value_pos_1,date_pos_2,value_pos_2,date_pos_3,value_pos_3,date_pos_4,value_pos_4,date_pos_5,value_pos_5)
values(2011,'3','2946',sysdate,'5434',null,null,null,null,null,null,null,null)
into to_update (year, line,counter, date_pos_1,value_pos_1,date_pos_2,value_pos_2,date_pos_3,value_pos_3,date_pos_4,value_pos_4,date_pos_5,value_pos_5)
values(2011,'3','2947',sysdate,'11',sysdate,'123',null,null,null,null,null,null)
into to_update (year, line,counter, date_pos_1,value_pos_1,date_pos_2,value_pos_2,date_pos_3,value_pos_3,date_pos_4,value_pos_4,date_pos_5,value_pos_5)
values(2011,'3','2948',sysdate,'33',sysdate,'44',sysdate,'8908',null,null,null,null)
into to_update (year, line,counter, date_pos_1,value_pos_1,date_pos_2,value_pos_2,date_pos_3,value_pos_3,date_pos_4,value_pos_4,date_pos_5,value_pos_5)
values(2011,'3','2949',sysdate,'1',sysdate,'2',sysdate,'343',sysdate,'78',null,null)
select * from dualOk now what i want to do is to update table to_update fields where value_pos is NULL. To explain it better imagine
collums are from left to right in that order value_pos_1, value_pos_2, value_pos_3 .... Now i would want to check for each row
if value_pos_1 is null ... if it is then update. Finist with this row and move to the next. If its not move to value_pos_2 in
same row and again check if its null. If it is ... update, if not, again move forward. Each cullum value_pos_X has a cullom date_pos_x
which has to be updated same as Value_pos_ cullums (if value_pos_X is null then coresponding date_pos_X will be null as well - thats
a fact in my table).
So is this doable by using only one update?
I manage to write a select statment using case clause which does those things perfectly only for value_pos_X fields. I wonder if i can use it in my
update statment?
select
case when a.value_pos_1 is  null then b.value else
     case when a.value_pos_2 is  null then b.value else
          case when a.value_pos_3 is  null then b.value else
               case when a.value_pos_4 is  null then b.value else
                    case when a.value_pos_5 is  null then b.value else to_number('99999','9999,99')
end
end
end
end
end  as value
from to_update a,t_employe b
where a.year = b.year
and a.line= b.line
and a.counter = b.counter Any suggestions how to pull this one of?
Thank you!

Answer 1

SQL> select  *
  2    from  to_update
  3  /
      YEAR L    COUNTER DATE_POS_ VALUE_POS_1 DATE_POS_ VALUE_POS_2 DATE_POS_ VALUE_POS_3 DATE_POS_ VALUE_POS_4 DATE_POS_ VALUE_POS_5
      2011 3       2946 27-AUG-11        5434
      2011 3       2947 27-AUG-11          11 27-AUG-11         123
      2011 3       2948 27-AUG-11          33 27-AUG-11          44 27-AUG-11        8908
      2011 3       2949 27-AUG-11           1 27-AUG-11           2 27-AUG-11         343 27-AUG-11          78
SQL> merge
  2    into to_update a
  3    using (
  4           select  a.rowid rid,
  5                   b.value
  6             from  to_update a,
  7                   t_employe b
  8             where a.year = b.year
  9               and a.line= b.line
10               and a.counter = b.counter
11          ) b
12     on (
13         a.rowid = b.rid
14        )
15     when matched then update set value_pos_1 = nvl2(value_pos_1,value_pos_1,b.value),
16                                  value_pos_2 = nvl2(value_pos_1,nvl2(value_pos_2,value_pos_2,b.value),value_pos_2),
17                                  value_pos_3 = nvl2(value_pos_1 + value_pos_2,nvl2(value_pos_3,value_pos_3,b.value),value_pos_3),
18                                  value_pos_4 = nvl2(value_pos_1 + value_pos_2 + value_pos_3,nvl2(value_pos_4,value_pos_4,b.value),value_pos_4),
19                                  value_pos_5 = nvl2(value_pos_1 + value_pos_2 + value_pos_3 + value_pos_4,nvl2(value_pos_5,value_pos_5,b.value),value_pos_5)
20  /
4 rows merged.
SQL> select  *
  2    from  to_update
  3  /
      YEAR L    COUNTER DATE_POS_ VALUE_POS_1 DATE_POS_ VALUE_POS_2 DATE_POS_ VALUE_POS_3 DATE_POS_ VALUE_POS_4 DATE_POS_ VALUE_POS_5
      2011 3       2946 27-AUG-11        5434                  3344
      2011 3       2947 27-AUG-11          11 27-AUG-11         123                  4433
      2011 3       2948 27-AUG-11          33 27-AUG-11          44 27-AUG-11        8908                  4455
      2011 3       2949 27-AUG-11           1 27-AUG-11           2 27-AUG-11         343 27-AUG-11          78                  5544
SQL> Or yhis might be more readable:
merge
  into to_update a
  using (
         select  a.rowid rid,
                 b.value
           from  to_update a,
                 t_employe b
           where a.year = b.year
             and a.line= b.line
             and a.counter = b.counter
        ) b
   on (
       a.rowid = b.rid
   when matched then update set value_pos_1 = case when value_pos_1 is null then b.value else value_pos_1 end,
                                value_pos_2 = case when value_pos_1 is not null and value_pos_2 is null then b.value else value_pos_2 end,
                                value_pos_3 = case when value_pos_1 + value_pos_2 is not null and value_pos_3 is null then b.value else value_pos_3 end,
                                value_pos_4 = case when value_pos_1 + value_pos_2 + value_pos_3 is not null and value_pos_4 is null then b.value else value_pos_4 end,
                                value_pos_5 = case when value_pos_1 + value_pos_2 + value_pos_3 + value_pos_4 is not null and value_pos_5 is null then b.value else value_pos_5 end
/SY.