Re: how to count elapsed time between sysdate and some saved timestamp?

On May 7, 4:45 pm, "fitzjarr..._at_cox.net" <orat..._at_msn.com> wrote:
> On May 7, 3:08 pm, Mark D Powell <Mark.Pow..._at_eds.com> wrote:
>
>
>
> > On May 7, 3:52 pm, "fitzjarr..._at_cox.net" <orat..._at_msn.com> wrote:
>
> > > On May 7, 12:51 pm, sybra..._at_hccnet.nl wrote:
>
> > > > On Wed, 7 May 2008 18:45:04 +0200, "buu" <a..._at_a.com> wrote:
> > > > >question is simple... I have an date field in an table and I would like to
> > > > >measure time difference (minutes or sec.) between current time and that
> > > > >field.
>
> > > > >at wich way you propose?
>
> > > > Assuming a non-paleolithic version of Oracle (I appreciate, you, as
> > > > someone asking help, can't be bothered to post it, as you assume
> > > > Oracle never changes), one would just subtract the two dates (the unit
> > > > of a date is a day), so you get the difference expressed as a days
> > > > fraction and feed that through the numtodsinterval function.
>
> > > > --
> > > > Sybrand Bakker
> > > > Senior Oracle DBA
>
> > > With many thanks to William Robertson for sharing this on his Oracle
> > > WTF site.
>
> > > <sarcasm>
> > > Oh, but it's much more fun to make things complicated:
>
> > > SQL> --
> > > SQL> -- Let's build a package of convoluted
> > > SQL> -- mathematical il-logic to return what
> > > SQL> -- would normally be the result of a
> > > SQL> -- simple subtraction of dates
> > > SQL> --
> > > SQL> --
> > > SQL> -- You simply can't beat complexity
> > > SQL> --
> > > SQL> -- Many thanks to William Robertson
> > > SQL> -- for bringing this exquisite example
> > > SQL> -- to my attention and for providing
> > > SQL> -- the table population code
> > > SQL> --
> > > SQL>
> > > SQL> CREATE PACKAGE dates_pkg
> > >   2  AS
> > >   3      FUNCTION julian_date
> > >   4          ( date_to_convert DATE )
> > >   5          RETURN NUMBER;
> > >   6
> > >   7      FUNCTION minutes_since_midnight
> > >   8          ( timevalue DATE )
> > >   9          RETURN NUMBER;
> > >  10
> > >  11      FUNCTION minutes_elapsed
> > >  12          ( lowdate DATE
> > >  13          , highdate DATE )
> > >  14          RETURN NUMBER;
> > >  15
> > >  16  END dates_pkg;
> > >  17  /
>
> > > Package created.
>
> > > Elapsed: 00:00:00.01
> > > SQL>
> > > SQL> CREATE PACKAGE BODY dates_pkg
> > >   2  AS
> > >   3      FUNCTION julian_date
> > >   4          ( date_to_convert DATE)
> > >   5          RETURN NUMBER
> > >   6      IS
> > >   7          varch_value VARCHAR (10);
> > >   8          num_value NUMBER (20);
> > >   9      BEGIN
> > >  10          --
> > >  11          -- First, we take a date and convert it to a date by
> > > converting it
> > >  12          -- to a character string using the same format we will use
> > > to
> > >  13          -- convert it BACK to a date again
> > >  14          --
> > >  15          -- Oh, then we convert it back to a character string
> > >  16          --
> > >  17          -- In Julian format, which is a number
> > >  18          --
> > >  19          SELECT TO_CHAR
> > >  20                 ( TO_DATE(TO_CHAR(date_to_convert,'MM/DD/YYYY'),'MM/DD/
> > > YYYY')
> > >  21                 , 'J')
> > >  22          INTO   varch_value
> > >  23          FROM   dual;
> > >  24
> > >  25          --
> > >  26          -- Okay, so we had a Julian date as a number but we changed
> > > it to
> > >  27          -- a character string so we could go back and make it a ...
> > >  28          -- NUMBER ... again
> > >  29          --
> > >  30          SELECT TO_NUMBER (varch_value)
> > >  31          INTO   num_value
> > >  32          FROM   dual;
> > >  33
> > >  34          --
> > >  35          -- So, we finally make up our mind and keep it a number and
> > >  36          -- return it from the function
> > >  37          --
> > >  38          RETURN (num_value);
> > >  39      END julian_date;
> > >  40
> > >  41
> > >  42      FUNCTION minutes_since_midnight (
> > >  43          timevalue DATE)
> > >  44          RETURN NUMBER
> > >  45      IS
> > >  46          secs_elapsed NUMBER (20);
> > >  47          mins_elapsed NUMBER (20);
> > >  48      BEGIN
> > >  49          --
> > >  50          -- So now we take a date and extract the time portion of
> > > it,
> > >  51          -- convert that BACK to a date, then convert THAT to a
> > > string
> > >  52          -- of seconds and convert THAT to a number
> > >  53          --
> > >  54          -- Is it me, or are we essentially driving across town just
> > > to
> > >  55          -- go next door?
> > >  56          --
> > >  57          SELECT TO_NUMBER
> > >  58                 ( TO_CHAR(TO_DATE(TO_CHAR(timevalue,'HH:MI AM'),'HH:MI AM')
> > >  59                 , 'SSSSS') )
> > >  60          INTO   secs_elapsed
> > >  61          FROM   dual;
> > >  62
> > >  63          --
> > >  64          -- Oooo, now we divide that total number of seconds by ...
> > >  65          -- wait for it ...
> > >  66          -- any second now ...
> > >  67          -- 60!  Who would have thought that 60 seconds equals
> > >  68          -- one minute?
> > >  69          --
> > >  70          SELECT (secs_elapsed / 60)
> > >  71          INTO   mins_elapsed
> > >  72          FROM   dual;
> > >  73
> > >  74          --
> > >  75          -- Before we rest on our laurels we return the minutes
> > > since midnight
> > >  76          --
> > >  77          RETURN (mins_elapsed);
> > >  78      END minutes_since_midnight;
> > >  79
> > >  80
> > >  81      FUNCTION minutes_elapsed
> > >  82          ( lowdate DATE
> > >  83          , highdate DATE )
> > >  84          RETURN NUMBER
> > >  85      IS
> > >  86          final_number NUMBER (20);
> > >  87          low_julian NUMBER (20);
> > >  88          high_julian NUMBER (20);
> > >  89          num_days NUMBER (20);
> > >  90          num_minutes NUMBER (20);
> > >  91          temp_mins NUMBER (20);
> > >  92          min_low NUMBER (20);
> > >  93          min_high NUMBER (20);
> > >  94      BEGIN
> > >  95          --
> > >  96          -- Now, why didn't we use this julian_date function in the
> > >  97          -- last installment of Julian conversions?
> > >  98          --
> > >  99          -- Oh, yeah, because we just WROTE that wonderful function
> > > 100          --
> > > 101          -- So, okay, we take our date values and return the Julian
> > > 102          -- representations of them using all of the mathematical
> > > 103          -- aerobics from earlier
> > > 104          --
> > > 105          -- I guess this is so much easier than simply subtracting
> > > 106          -- them
> > > 107          --
> > > 108          SELECT julian_date (lowdate)
> > > 109          INTO   low_julian
> > > 110          FROM   dual;
> > > 111
> > > 112          SELECT julian_date (highdate)
> > > 113          INTO   high_julian
> > > 114          FROM   dual;
> > > 115
> > > 116          --
> > > 117          -- Woo-hoo! Higher math time!  Subtract the Julian dates
> > > 118          -- and get the number of days
> > > 119          --
> > > 120          -- Isn't that what we'd get if we just subtracted the
> > > 121          -- submitted dates as-is?
> > > 122          --
> > > 123          -- Of course it is
> > > 124          --
> > > 125          SELECT (high_julian - low_julian)
> > > 126          INTO   num_days
> > > 127          FROM   dual;
> > > 128
> > > 129          --
> > > 130          -- Now we calculate the total minutes elapsed
> > > 131          -- using our values generated by our extreme
> > > 132          -- gyrations
> > > 133          --
> > > 134          -- I'm out of breath just thinking about all of this work
> > > 135          --
> > > 136          SELECT (num_days * 1440)
> > > 137          INTO   num_minutes
> > > 138          FROM   dual;
> > > 139
> > > 140          --
> > > 141          -- And now we put those other mathematical moves
> > > 142          -- to use
> > > 143          --
> > > 144          -- Tell me again why we think we're smarter than
> > > 145          -- the average bear?
> > > 146          --
> > > 147          SELECT minutes_since_midnight (lowdate)
> > > 148          INTO   min_low
> > > 149          FROM   dual;
> > > 150
> > > 151          SELECT minutes_since_midnight (highdate)
> > > 152          INTO   min_high
> > > 153          FROM   dual;
> > > 154
> > > 155          --
> > > 156          -- Now this is disgusting
> > > 157          --
> > > 158          -- Using a TEMP variable to aid in simple mathematical
> > > 159          -- processing
> > > 160          --
> > > 161          SELECT (min_high - min_low)
> > > 162          INTO   temp_mins
> > > 163          FROM   dual;
> > > 164
> > > 165          --
> > > 166          -- And this is better than:
> > > 167          -- select (end_date - start_date)*1440 because?
> > > 168          --
> > > 169          SELECT (num_minutes + temp_mins)
> > > 170          INTO   final_number
> > > 171          FROM   dual;
> > > 172
> > > 173          RETURN (final_number);
> > > 174
> > > 175      END minutes_elapsed;
> > > 176  END dates_pkg;
> > > 177  /
>
> > > Package body created.
>
> > > Elapsed: 00:00:00.04
> > > SQL>
> > > SQL> --
> > > SQL> -- This is more fun with a test table
> > > SQL> --
> > > SQL>
> > > SQL> create table date_tst ( start_dt date, end_dt date);
>
> > > Table created.
>
> > > Elapsed: 00:00:00.01
> > > SQL>
> > > SQL> insert into date_tst
> > >   2  select date '2006-12-25' + dbms_random.value(1,365)
> > >   3       , date '2007-12-25' + dbms_random.value(1,365)
> > >   4  FROM   dual connect by level <= 4000;
>
> > > 4000 rows created.
>
> ...
>
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>
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I was thinking timestamp because of the subject line. It is probably just a saved date so only simple date math is required though I alwyas have a heck of a time constructing simple date math when you want hours, minutes, seconds broken out. Eventually I get the mods, commas, and parenthesis correct.

• Mark D Powell --