Обсуждение: Timestamp vs. Interval and formatting....

Hello,

I've been building an application to catalog my CD collection, and have
been merrily adding the track lengths to a field of type "interval".
This seemed to make the most sense if I wanted to do math on them  (ie.
totals) later on.  Everything was working well until I realized that
tracks over 24 minutes were being returned as "1 day HH:MM".  What is
the easiest way to limit the field to MM:SS?

I noticed that the "to_char" function for intervals is deprecated.
Is timestamp a better choice for this field after all?

Thanks,
Dan J.

_________________
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Hi Dan,

On Jan 4, 2004, at 2:11 PM, Dan Jewett wrote:
> I've been building an application to catalog my CD collection, and have
> been merrily adding the track lengths to a field of type "interval".
> This seemed to make the most sense if I wanted to do math on them  (ie.
> totals) later on.  Everything was working well until I realized that
> tracks over 24 minutes were being returned as "1 day HH:MM".  What is
> the easiest way to limit the field to MM:SS?

As you've noticed, your intention of inserting MM:SS is being
interpreted by PostgreSQL as HH::MM instead. Here's what worked for me:

test=# create table track_length (trackid int, length interval);
CREATE TABLE
test=# insert into track_length values (1,'1 min 32 sec');
INSERT 1196294 1
test=# select * from track_length;
  trackid |  length
---------+----------
        1 | 00:01:32
(1 row)

Your system is probably more complex than this, but you can see how it
works. Check out the following link for more details.

<http://www.postgresql.org/docs/current/static/datatype-
datetime.html#AEN4289>

Does this help?

Michael Glaesemann
grzm myrealbox com

On Sun, 4 Jan 2004 14:47:49 -0600, Michael Glaesemann wrote this well
considered message:
> Hi Dan,
>
> On Jan 4, 2004, at 2:11 PM, Dan Jewett wrote:
>> I've been building an application to catalog my CD collection, and have
>> been merrily adding the track lengths to a field of type "interval".
>> This seemed to make the most sense if I wanted to do math on them  (ie.
>> totals) later on.  Everything was working well until I realized that
>> tracks over 24 minutes were being returned as "1 day HH:MM".  What is
>> the easiest way to limit the field to MM:SS?
>
> As you've noticed, your intention of inserting MM:SS is being
> interpreted by PostgreSQL as HH::MM instead. Here's what worked for
> me:
>
> test=# create table track_length (trackid int, length interval);
> CREATE TABLE
> test=# insert into track_length values (1,'1 min 32 sec');
> INSERT 1196294 1
> test=# select * from track_length;
>  trackid |  length
> ---------+----------
>        1 | 00:01:32
> (1 row)
>
> Your system is probably more complex than this, but you can see how
> it works. Check out the following link for more details.
>
>
<http://www.postgresql.org/docs/current/static/datatype-datetime.html#AEN4289>
>
> Does this help?
>
> Michael Glaesemann
> grzm myrealbox com
>

Hello Michael,

Yes I had seen the scenario you describe in the docs, and I was hoping
I wouldn't have to add the step of exploding the time string on the
colon in PHP in order to set up the 'xx min xx sec' string for
Postgres.  Your post did tip me off to the shortcut of simply setting
up the length variable thusly:

$trk_length = "00:" . $length;

Postgres accepts HH:MM:SS for the interval type so you don't have to
explicitly name the units.  Since all the times coming from iTunes
(where I'm getting the info) are in the format MM:SS, I just needed to
prepend them with the HH part.

Now I just have the issue of resetting all those times I already
entered which were HH:MM instead of MM:SS.

Thanks,
Dan J.

Hi Dan,

On Jan 4, 2004, at 7:30 PM, Dan Jewett wrote:

> On Sun, 4 Jan 2004 14:47:49 -0600, Michael Glaesemann wrote this well
> considered message:

You certainly know how to flatter a guy! :)

> Now I just have the issue of resetting all those times I already
> entered which were HH:MM instead of MM:SS.

This is just thinking out loud: I haven't tried it. Can you do
something like this?

UPDATE track_length SET length = (
    SELECT EXTRACT(hour FROM length)::min + EXTRACT(min FROM length)::sec
    FROM track_length);

I'm not sure about the casts as they are, but there should be a way to
do that. There was just a post that had a subquery used to get a value
on a update, so I'm not sure that'd work either, but might be worth a
shot.

FWIW,

Michael Glaesemann
grzm myrealbox com

On Jan 5, 2004, at 12:13 AM, Michael Glaesemann wrote:

> Hi Dan,
>
> On Jan 4, 2004, at 7:30 PM, Dan Jewett wrote:
>
>> On Sun, 4 Jan 2004 14:47:49 -0600, Michael Glaesemann wrote this well
>> considered message:
>
> You certainly know how to flatter a guy! :)
>
>> Now I just have the issue of resetting all those times I already
>> entered which were HH:MM instead of MM:SS.
>
> This is just thinking out loud: I haven't tried it. Can you do
> something like this?
>
> UPDATE track_length SET length = (
>     SELECT EXTRACT(hour FROM length)::min + EXTRACT(min FROM length)::sec
>     FROM track_length);

On second thought, I think this SELECT isn't specific enough. This
should be better:

UPDATE track_length
SET length = (EXTRACT(hour FROM length)::min + EXTRACT(min FROM
LENGTH)::sec)

Still not sure of the casts, but I think it's closer.

Michael Glaesemann
grzm myrealbox com