One merge instead of three different

Question

Hi all,
My need is to calculate rows and write result into column:
c1 if current month is 1st in quarter,
c2 if current month is 2nd in quarter,
c3 if current month is 3rd in quarter.
For example, today is August, it's the second month in quarter, so I should write my value into c2 column.
In my example below the result is just one row:
select 111 as id, 1 as c1, 0 as c2, 0 as c3 from dualMy real result is much bigger, so I use merge to insert (is id is new) or to update (if id is already present in table).
The question is how do I perform this using one merge instead of three different. In case it's possible at all, of course.
CREATE TABLE marco_tmp_010811b
    (id                             NUMBER(9,0) PRIMARY KEY,
     c1                             NUMBER(15,0) NOT NULL,
     c2                             NUMBER(15,0) NOT NULL,
     c3                             NUMBER(6,0) NOT NULL);
begin
if months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 0 then
merge into marco_tmp_010811b rr
  using
  (select 111 as id, 1 as c1, 0 as c2, 0 as c3 from dual) hh
on (hh.id = rr.id)
when matched then update set rr.c1 = rr.c1 + hh.c1
when not matched then insert (rr.id, rr.c1, rr.c2, rr.c3)
                      values (hh.id, hh.c1, hh.c2, hh.c3);
end if;
if months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 1 then
merge into marco_tmp_010811b rr
  using
  (select 111 as id, 0 as c1, 1 as c2, 0 as c3 from dual) hh
on (hh.id = rr.id)
when matched then update set rr.c2 = rr.c2 + hh.c2
when not matched then insert (rr.id, rr.c1, rr.c2, rr.c3)
                      values (hh.id, hh.c1, hh.c2, hh.c3);
end if;
if months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 2 then
merge into marco_tmp_010811b rr
  using
  (select 111 as id, 0 as c1, 0 as c2, 1 as c3 from dual) hh
on (hh.id = rr.id)
when matched then update set rr.c3 = rr.c3 + hh.c3
when not matched then insert (rr.id, rr.c1, rr.c2, rr.c3)
                      values (hh.id, hh.c1, hh.c2, hh.c3);
end if;
end;

Answer 1

Can be also like this
begin
     merge into marco_tmp_010811b rr
     using
          select
               111 as id,
               case when months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 0 then 1 else 0 as c1,
               case when months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 1 then 1 else 0 as c2,
               case when months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 2 then 1 else 0 as c3
          from dual
     ) hh
     on (hh.id = rr.id)
     when matched then
     update set
          rr.c1 =
          CASE WHEN months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 0 THEN rr.c1 + hh.c1 ELSE rr.c1 END,
          rr.c2 =
          CASE WHEN months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 1 THEN rr.c2 + hh.c2 ELSE rr.c2 END,
          rr.c3 =
          CASE WHEN months_between(trunc(sysdate+125,'MM'),trunc(sysdate+125,'Q')) = 2 THEN rr.c3 + hh.c3 ELSE rr.c3 END
     when not matched then
          insert (rr.id, rr.c1, rr.c2, rr.c3)
          values (hh.id, hh.c1, hh.c2, hh.c3);     
end;In different IF conditions, we have to make sure that other column value should not be changing,
So in the else condition of CASE in the UPDATE section we will be using the current value of the column.
Edited by: bpat on Aug 1, 2011 10:23 AM