Help with a update,select statement

Question

Hi all please can you help me with a update statement i am struggling with.
I have 2 tables
Holiday and data
In the Holiday table i have columns for
Machine_ID NUMBER,
date_from DATE,
date_to DATE,
ID NUMBER
Machine column represents a type of machine, the two dates represent the start and end date of a holiday and ID represents the ID of the machines that the holiday effects (as you can have many machines that are the same, so the ID unique field to seperate them.
i.e.
996     25-DEC-08 00:00:00     27-DEC-08 00:00:00     91     
996     25-DEC-08 00:00:00     27-DEC-08 00:00:00     92     
100     28-DEC-08 00:00:00     29-DEC-08 00:00:00     1
100     28-DEC-08 00:00:00     29-DEC-08 00:00:00     2
In the data table i have the following columns:
DATE DATE
Machine NUMBER
SHIFT1S DATE
SHIFT1F DATE
SHIFT2S DATE
SHIFT2F DATE
CALS DATE
CALF DATE
CAP NUMBER
CALCAP NUMBER
total_hrs_up NUMBER
In here i have data for every date in the calendar. The machines are cross references with the machine in holidays table.
I run two shifts so have shift 1 start, finish. shift 2 start, finish. These are dates with times, so shift1s could be 01-01-08 09:00:00 shift1f could be 01-01-08 17:00:00.
shift2S could be 01-01-08 21:00:00 shift2f could be 01-01-08 23:59:00.
so that machine would be up between them hours of the day.
Other columns include
CALS, ,CALF = calendar start, finish, - This needs to be populated from the holiday table. currently null. So if the date is the 26 DEC and the machine is the same as what is in the holiday table then these two columns should be populated with them data
CAP is the total number of these machines i have available.
CALCAP is the no of machines the holiday affects -currently null
total_hrs_up is the number of hours this machine is up and running -currently null.
So what i need to do is populate the cals, calf calcap, total_hrs_up columns.
total_hrs_up is the important one, this needs to work out based on the two shift patterns the number of hours that the machine is available and then take off the holiday hours to give a final value.
so current data example in data is
date machine shifts shiftf shift2s shift2f cals, calf, cap, calcap, total_hrs
16-JUL-08     100 09:00:00     17:00:00     12:00:00     00:00:00               '','','',1     ,''     
16-JUL-08     105 09:00:00     17:00:00     12:00:00     00:00:00               '','','',1     ,''
16-JUL-08     107 09:00:00     17:00:00     12:00:00     00:00:00               '','','',1     ,''
id like to see based on the holiday table if there is a holiday then this data is updated as such and a total_hrs machine is available populated on that date.
Any help is very much appreciated!
Thanks

Answer 1

Hi,
The following query does what you requested.
It makes the following assumptions:
(a) in data, shift1start <= shift1finish
(b) in holiday, hol_start <= hol_finish
(b) in data, the combination (machine, shift1start) is unique
(c) in holiday, hol_start <= hol_finish
(d) in holiday, rows for the same machine and id never have overlapping dates (including times). For example:
INSERT INTO holiday (machine, id, date_from, date_to)
VALUES (200, 1, '26-DEC-08 07:00:00', '26-DEC-08 09:59:59');
INSERT INTO holiday (machine, id, date_from, date_to)
VALUES (200, 1, '26-DEC-08 09:00:00', '26-DEC-08 09:59:59');will cause a probem. Multiple rows for the same machine and day are okay, however, if the times do not overlap, like the following:
INSERT INTO holiday (machine, id, date_from, date_to)
VALUES (200, 1, '26-DEC-08 07:00:00', '26-DEC-08 08:59:59');
INSERT INTO holiday (machine, id, date_from, date_to)
VALUES (200, 1, '26-DEC-08 09:00:00', '26-DEC-08 09:59:59');Here's the UPDATE statement:
UPDATE     data     m
SET     (     hol_start
     ,     hol_finish
     ,     no_of_available_minutes
     ) =
(     SELECT     MIN (date_from)
     ,     MAX (date_to)
     ,     (     MAX (shift1finish - shift1start)     -- Total from data
          -     ( NVL     ( SUM     ( LEAST (date_to, shift1finish)
                         - GREATEST (date_from, shift1start)
                    , 0
                    )                    -- Total from holiday
               / MAX (total_no_of_machines)          -- Average
          ) * 24 * 60                         -- Convert days to minutes
     FROM          data     d
     LEFT OUTER JOIN     holiday     h     ON     h.machine     = d.machine
                         AND NOT     (     date_from     > shift1finish
                              OR      date_to          < shift1start
     WHERE          d.machine     = m.machine
     AND          d.shift1start     = m.shift1start
);The subquery has to use its own copy of data (that is, in needs d, not m), since the subquery has to return a non-NULL number of minutes when no rows in h match m.