Question

I have a table like the following, each entry a change in STATUS on the given time.
The status can be repeated because other columns have sub-status information.

How can I get a percentage time for each status by, say, hour?

NAME STATUS_CHANGE_TIME  STATUS
foo  15-MAY-11 18:52     A
foo  15-MAY-11 18:38     A
foo  15-MAY-11 18:33     B
foo  15-MAY-11 16:53     A
foo  15-MAY-11 16:47     B
foo  15-MAY-11 13:37     A
foo  15-MAY-11 13:33     C
foo  15-MAY-11 10:23     C
foo  15-MAY-11 10:17     A
foo  ...

Desired return:

HH24  STATUS  PERCENT    
10  ...
11    C       100        (No entries; last change was to C)
12    C       100        ""                       ""
13    C        62
13    A        38        (From C to A at :37 with 23 mins left; 23/60 ~ 38%)
14    A       100
15    A       100
16    A        90        (= A for first 47 minutes, then for another 7)
16    B        10        (16:53 - 16:47 = 6 minutes or 10% of an hour)
17    A       100
18 ... etc.

Answer 1

Great question, this was an interesting challenge!

What you need is an ancillary table to store each time division (in this case, hours), then join to it where the status updates overlap. LEAD() can grab the next status entry to check when it was, and GREATEST() and LEAST() can figure out which time is applicable for the start/end of the status for each hour.

Of course, this is much easier explained in an example. Here is the HOURS table needed:

SQL> CREATE TABLE hours (HOUR NUMBER(2), start_m date, end_m date);

Table created.

SQL> BEGIN
  2      FOR i IN 0..23 LOOP
  3          INSERT INTO hours VALUES(i, to_date(lpad(i, 2, '0')||':00:00', 'HH24:MI:SS')
  4                                    , to_date(lpad(i, 2, '0')||':59:59', 'HH24:MI:SS'));
  5      END loop;
  6      COMMIT;
  7  END;
  8  /

PL/SQL procedure successfully completed.

The following is just population of your test data from your question.

SQL> CREATE TABLE status_updates (NAME VARCHAR2(3), status_change_time DATE, status CHAR(1));

Table created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 18:52', 'DD-MON-RR HH24:MI:SS'), 'A');

1 row created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 18:38', 'DD-MON-RR HH24:MI:SS'), 'A');

1 row created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 18:33', 'DD-MON-RR HH24:MI:SS'), 'B');

1 row created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 16:53', 'DD-MON-RR HH24:MI:SS'), 'A');

1 row created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 16:47', 'DD-MON-RR HH24:MI:SS'), 'B');

1 row created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 13:37', 'DD-MON-RR HH24:MI:SS'), 'A');

1 row created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 13:33', 'DD-MON-RR HH24:MI:SS'), 'C');

1 row created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 10:23', 'DD-MON-RR HH24:MI:SS'), 'C');

1 row created.

SQL> INSERT INTO status_updates VALUES ('foo',TO_DATE('15-MAY-11 10:17', 'DD-MON-RR HH24:MI:SS'), 'A');

1 row created.

SQL> commit;

Commit complete.

Now here is the select statement to get the required percentages.

SELECT t.NAME, t.HOUR, t.status, sum(round((status_end_h-start_status_h)*24*100)) per_cent
FROM   (
    SELECT A.NAME
    ,      A.status
    ,      A.status_change_time
    ,      A.next_change_time
    ,      b.HOUR
    ,      greatest(status_change_time, trunc(status_change_time)+(b.start_m-trunc(b.start_m))) start_status_h
    ,      least(next_change_time, trunc(next_change_time)+(b.end_m-trunc(b.end_m))) status_end_h
    FROM   (
        SELECT NAME
        ,      status
        ,      status_change_time
        ,      lead(status_change_time) OVER (ORDER BY NAME, status_change_time) next_change_time
        FROM   status_updates
    ) A, hours b
    WHERE  TO_CHAR(b.start_m, 'HH24:MI:SS') BETWEEN TO_CHAR(A.status_change_time, 'HH24:MI:SS') AND TO_CHAR(A.next_change_time, 'HH24:MI:SS')
    OR     TO_CHAR(b.end_m, 'HH24:MI:SS') BETWEEN TO_CHAR(A.status_change_time, 'HH24:MI:SS') AND TO_CHAR(A.next_change_time, 'HH24:MI:SS')
    OR    (TO_CHAR(A.status_change_time, 'HH24:MI:SS') BETWEEN TO_CHAR(b.start_m, 'HH24:MI:SS') AND TO_CHAR(b.end_m, 'HH24:MI:SS')
    AND    TO_CHAR(A.next_change_time, 'HH24:MI:SS') BETWEEN TO_CHAR(b.start_m, 'HH24:MI:SS') AND TO_CHAR(b.end_m, 'HH24:MI:SS'))
) t
GROUP BY t.NAME, t.HOUR, t.status
ORDER BY t.HOUR;

NAM       HOUR S   PER_CENT                                                     
--- ---------- - ----------                                                     
foo         10 A         10                                                     
foo         10 C         62                                                     
foo         11 C        100                                                     
foo         12 C        100                                                     
foo         13 A         38                                                     
foo         13 C         62                                                     
foo         14 A        100                                                     
foo         15 A        100                                                     
foo         16 A         90                                                     
foo         16 B         10                                                     
foo         17 A        100                                                     

NAM       HOUR S   PER_CENT                                                     
--- ---------- - ----------                                                     
foo         18 A         78                                                     
foo         18 B          8                                                     

13 rows selected.