Update statement conditioned on two columns but for certain values only

Question

Hi this is my my sample data:
with Table_1       
as
      select '20:00' incident_time, 'WEDNESDAY' Day, 'N' Weekend,  '' Weekend_Alt   from dual
      union all
      select '18:00' incident_time, 'SATURDAY' Day, 'Y' Weekend,  '' Weekend_Alt from dual
      union all
      select '19:00' incident_time, 'FRIDAY' Day, 'N' Weekend, '' Weekend_Alt from dual
      union all
      select '11:00' incident_time, 'FRIDAY' Day, 'N' Weekend, '' Weekend_Alt from dual
select *
  from Table_1I want to perform an update as seen below
Update Table_1 tt
SET Weekend_Alt = (CASE WHEN TO_CHAR(tt.day,'fmDAY') IN ('FRIDAY AND TIME >= 19:00','SATURDAY','SUNDAY') THEN 'Y' ELSE 'N' END)
I realize the syntax is wrong but just want to give you an idea of what I want to achieve.Final Result should look something like this:
with Table_1       
as
      select '20:00' incident_time, 'WEDNESDAY' Day, 'N' Weekend,  'N' Weekend_Alt   from dual
      union all
      select '18:00' incident_time, 'SATURDAY' Day, 'Y' Weekend,  'Y' Weekend_Alt from dual
      union all
      select '19:00' incident_time, 'FRIDAY' Day, 'N' Weekend, 'Y' Weekend_Alt from dual
      union all
      select '11:00' incident_time, 'FRIDAY' Day, 'N' Weekend, 'N' Weekend_Alt from dual
select *
  from Table_1Thanks in advance!!!
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Answer 1

with Table_1
as
      select to_date('01-JUL-2009 20:10','DD-MON-YYYY HH24:MI') incident_date    from dual
      union all
      select to_date('23-MAR-2010 12:12','DD-MON-YYYY HH24:MI') incident_date from dual
      union all
      select to_date('25-JUL-2010 23:30','DD-MON-YYYY HH24:MI') incident_datet from dual
      union all
      select to_date('09-JAN-2010 08:30','DD-MON-YYYY HH24:MI') incident_date from dual
      union all
      select to_date('08-JAN-2010 08:30','DD-MON-YYYY HH24:MI') incident_date from dual
      union all
      select to_date('08-JAN-2010 20:30','DD-MON-YYYY HH24:MI') incident_date from dual
      union all
      select to_date('26-JUL-2010 00:00','DD-MON-YYYY HH24:MI') incident_datet from dual
select incident_date, to_char(incident_date,'Day'),
    case
        when incident_date between trunc(incident_date,'IW') + 4 + 19/24
                               and trunc(incident_date,'IW') + 7
        then 'Y' else 'N'
    end
from Table_1 t;So your update would be
update table_1 tt
set weekend_alt =
    case
        when incident_date between trunc(incident_date,'IW') + 4 + 19/24
                               and trunc(incident_date,'IW') + 7
        then 'Y' else 'N'
    end;But it does lead me to question whether it is a good idea to store this derived data
Edited by: 3360 on Nov 8, 2011 10:14 AM