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# 1  
Old 04-17-2013
PL/SQL heartbeat Query has errors
Hello, I want to query something simple which works as a standalone sqlplus query perfectly:

Table statements:
Code:
ALTER TABLE MP$PATHLOADER.ISALIVE
 DROP PRIMARY KEY CASCADE;

DROP TABLE MP$PATHLOADER.ISALIVE CASCADE CONSTRAINTS;

CREATE TABLE MP$PATHLOADER.ISALIVE
(
   ISALIVE_PK   NUMBER,
   INSERTTS     TIMESTAMP (6) NOT NULL,
   UPDATETS     TIMESTAMP (6) NOT NULL,
   VERSIONID    NUMBER NOT NULL,
   NAME         VARCHAR2 (256 CHAR) NOT NULL,
   ACTIVE       NUMBER (1) DEFAULT 0 NOT NULL
);


CREATE UNIQUE INDEX MP$PATHLOADER.ISALIVE_PK
   ON MP$PATHLOADER.ISALIVE (ISALIVE_PK);


ALTER TABLE MP$PATHLOADER.ISALIVE
ADD (  CONSTRAINT ISALIVE_PK PRIMARY KEY (ISALIVE_PK)
USING INDEX MP$PATHLOADER.ISALIVE_PK);

A Testvalue as follow:
Code:
Insert into MP$PATHLOADER.ISALIVE
   (ISALIVE_PK, 
    INSERTTS, UPDATETS, VERSIONID, NAME, ACTIVE)
 Values
   (3, TO_TIMESTAMP('01/21/2013 15:29:02,000000','MM/DD/YYYY HH24:MI:SS,FF'), TO_TIMESTAMP('01/24/2013 13:49:40,013000','MM/DD/YYYY HH24:MI:SS,FF'), 8781, '010123vb', 
    1);

And now the query for getting the differences in minutes between the timestamps:

Code:
(SELECT ABS (
             TO_NUMBER (TO_CHAR (updatets, 'dd')) * 24 * 60
           + TO_NUMBER (TO_CHAR (updatets, 'hh24')) * 60
           + TO_NUMBER (TO_CHAR (updatets, 'mi'))
           - TO_NUMBER (TO_CHAR (SYSDATE, 'dd')) * 24 * 60
           - TO_NUMBER (TO_CHAR (SYSDATE, 'hh24')) * 60
           - TO_NUMBER (TO_CHAR (SYSDATE, 'mi')))
           AS BACKLOG_MINUTES
   FROM MP$PATHLOADER.ISALIVE
  WHERE active = '1');

But then in a PL/SQL Script this does not further work anymore:

Code:
SET SERVEROUTPUT ON
SET FEEDBACK OFF

DECLARE
   CTABLES   VARCHAR2 (20);
BEGIN
   EXECUTE IMMEDIATE
      (SELECT ABS (
                   TO_NUMBER (TO_CHAR (updatets, 'dd')) * 24 * 60
                 + TO_NUMBER (TO_CHAR (updatets, 'hh24')) * 60
                 + TO_NUMBER (TO_CHAR (updatets, 'mi'))
                 - TO_NUMBER (TO_CHAR (SYSDATE, 'dd')) * 24 * 60
                 - TO_NUMBER (TO_CHAR (SYSDATE, 'hh24')) * 60
                 - TO_NUMBER (TO_CHAR (SYSDATE, 'mi')))
         INTO CTABLES
         FROM MP$PATHLOADER.ISALIVE
        WHERE active = '1');

   DBMS_OUTPUT.PUT_LINE (CTABLES);
END;
/

Could someone lend me his helping hand, please!

Thanks a lot!
# 2  
Old 04-17-2013
You did not mention how this did not work. Errors or Warnings if any?

By the way EXECUTE IMMEDIATE statement is usually used to execute a dynamic SQL statement or anonymous PL/SQL block.

So in your PL/SQL I guess it is not required:
Code:
SET SERVEROUTPUT ON
SET FEEDBACK OFF

DECLARE
   CTABLES   VARCHAR2 (20);
BEGIN
      SELECT ABS (
                   TO_NUMBER (TO_CHAR (updatets, 'dd')) * 24 * 60
                 + TO_NUMBER (TO_CHAR (updatets, 'hh24')) * 60
                 + TO_NUMBER (TO_CHAR (updatets, 'mi'))
                 - TO_NUMBER (TO_CHAR (SYSDATE, 'dd')) * 24 * 60
                 - TO_NUMBER (TO_CHAR (SYSDATE, 'hh24')) * 60
                 - TO_NUMBER (TO_CHAR (SYSDATE, 'mi')))
         INTO CTABLES
         FROM MP$PATHLOADER.ISALIVE
        WHERE active = '1';
   DBMS_OUTPUT.PUT_LINE (CTABLES);
END;
/

# 3  
Old 04-18-2013
Quote:
Originally Posted by sdohn
...And now the query for getting the differences in minutes between the timestamps:

Code:
(SELECT ABS (
             TO_NUMBER (TO_CHAR (updatets, 'dd')) * 24 * 60
           + TO_NUMBER (TO_CHAR (updatets, 'hh24')) * 60
           + TO_NUMBER (TO_CHAR (updatets, 'mi'))
           - TO_NUMBER (TO_CHAR (SYSDATE, 'dd')) * 24 * 60
           - TO_NUMBER (TO_CHAR (SYSDATE, 'hh24')) * 60
           - TO_NUMBER (TO_CHAR (SYSDATE, 'mi')))
           AS BACKLOG_MINUTES
   FROM MP$PATHLOADER.ISALIVE
  WHERE active = '1');

...
Difference between which two timestamps?
It obviously is not the difference between "updatets" and "insertts", because "insertts" is not being used in your query.
If you are trying to find out the difference between "updatets" and "sysdate" (or current time), then consider the output of the query:

Code:
SQL>
SQL> select * from isalive;
ISALIVE_PK INSERTTS                       UPDATETS                        VERSIONID NAME           ACTIVE
---------- ------------------------------ ------------------------------ ---------- ---------- ----------
         3 21-JAN-13 03.29.02.000000 PM   24-JAN-13 01.49.40.013000 PM         8781 010123vb            1
1 row selected.
SQL>
SQL>
SQL> SELECT ABS (
  2                   TO_NUMBER (TO_CHAR (updatets, 'dd')) * 24 * 60
  3                 + TO_NUMBER (TO_CHAR (updatets, 'hh24')) * 60
  4                 + TO_NUMBER (TO_CHAR (updatets, 'mi'))
  5                 - TO_NUMBER (TO_CHAR (SYSDATE, 'dd')) * 24 * 60
  6                 - TO_NUMBER (TO_CHAR (SYSDATE, 'hh24')) * 60
  7                 - TO_NUMBER (TO_CHAR (SYSDATE, 'mi'))
  8             )
  9             AS BACKLOG_MINUTES
 10     FROM ISALIVE
 11    WHERE active = '1';
 
BACKLOG_MINUTES
---------------
           9381
 
1 row selected.
 
SQL>
SQL>

The "updatets" shows a timestamp of 24-Jan-2013 and sysdate would be some day around 18-Apr-2013 (wherever you are on the planet Earth as of now). So the difference should be about 84 days, or 84*24*60 = 302400 minutes.

Since SYSDATE is like a "running target", let's use a fixed date to see how the query behaves. I'll use the date "2/24/2013 13:48:41" as my "current date" in the following query:

Code:
SQL>
SQL> select
  2         x + y + z               as min_1,
  3         p + q + r               as min_2,
  4         x + y + z - (p + q + r) as backlog_min
  5    from (
  6            SELECT
  7                   TO_NUMBER (TO_CHAR (updatets, 'dd')) * 24 * 60 as x,
  8                   TO_NUMBER (TO_CHAR (updatets, 'hh24')) * 60    as y,
  9                   TO_NUMBER (TO_CHAR (updatets, 'mi'))           as z,
 10                   --
 11                   TO_NUMBER (TO_CHAR (dt.now, 'dd')) * 24 * 60  as p,
 12                   TO_NUMBER (TO_CHAR (dt.now, 'hh24')) * 60     as q,
 13                   TO_NUMBER (TO_CHAR (dt.now, 'mi'))            as r
 14              FROM ISALIVE,
 15                   (
 16                     select TO_DATE('02/24/2013 13:48:41', 'MM/DD/YYYY HH24:MI:SS') as now from dual
 17                   ) dt
 18             WHERE active = '1'
 19         )
 20  /
 
     MIN_1      MIN_2 BACKLOG_MIN
---------- ---------- -----------
     35389      35388           1
 
1 row selected.
 
SQL>
SQL>
SQL>

Now, the difference between "24-JAN-2013 13:49:40" and "24-FEB-2013 13:48:41" is about 30 days, or approximately 30*24*60 = 43200 minutes but the query above returns exactly 1 minute as the difference.

The fallacy in the logic would be clear if you see what is being done here. Each date is converted to minutes from the start of its own month.
So "24-JAN-2013 13:49:40" is 35389 minutes from "1-JAN-2013".
And "24-FEB-2013 13:48:41" is 35388 minutes from "1-FEB-2013".
And so the difference is 1 minute.

So if the two dates ("updatets" and SYSDATE) lie in the same month, then you'll start counting from the same date (beginning of that month) and in that case your query will work. Otherwise it won't.

For example, if the "updatets" is, say, "31-MAR-2013 23:59:59" and you run your query just one second later (when the month has changed), then the result will be incorrect.

In Oracle, the difference between two DATEs is the number of days between them. If the difference has a fractional part, then that corresponds to the number of minutes and seconds in addition to the days in between. So, the difference in minutes between two DATEs is given by this expression -

Code:
(date_1 - date_2) * 24 * 60

Using this information, the query could be written thusly -

Code:
SQL>
SQL>
SQL> SELECT
  2         updatets,
  3         TO_CHAR (dt.now, 'DD-MON-YY HH:MI:SS AM') as now,
  4         (dt.now - CAST (updatets AS DATE))*24*60  as diff_in_min
  5    FROM ISALIVE,
  6         (
  7           select TO_DATE('02/24/2013 13:48:41', 'MM/DD/YYYY HH24:MI:SS') as now from dual
  8         ) dt
  9   WHERE active = '1'
 10  /
 
UPDATETS                       NOW                   DIFF_IN_MIN
------------------------------ --------------------- -----------
24-JAN-13 01.49.40.013000 PM   24-FEB-13 01:48:41 PM  44639.0167
 
1 row selected.
 
SQL>
SQL>

Another example where the difference is about 1 minute:

Code:
SQL>
SQL>
SQL> SELECT
  2         updatets,
  3         TO_CHAR (dt.now, 'DD-MON-YY HH:MI:SS AM') as now,
  4         (dt.now - CAST (updatets AS DATE))*24*60  as diff_in_min
  5    FROM ISALIVE,
  6         (
  7           select TO_DATE('01/24/2013 13:50:41', 'MM/DD/YYYY HH24:MI:SS') as now from dual
  8         ) dt
  9   WHERE active = '1'
 10  /
 
UPDATETS                       NOW                   DIFF_IN_MIN
------------------------------ --------------------- -----------
24-JAN-13 01.49.40.013000 PM   24-JAN-13 01:50:41 PM  1.01666667
 
1 row selected.
 
SQL>
SQL>
SQL>

I used the CAST function because the datatype of "updatets" is TIMESTAMP.
Accordingly, your query would be -

Code:
select (sysdate - cast(updatets as date))*24*60 as diff_in_min from isalive where active = '1';

Last edited by durden_tyler; 04-18-2013 at 03:10 AM..
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