Обсуждение: datetime query issue

I'm not sure how to go about this: I want to find all rows with a timestamp 
between, say 6 a.m. and 10 p.m. for any number of days. The column format is
datetime. How do I extract the 'time of the day' information from this
column? What I can think of is to create a view for every single day where datetime
is > 6 and < 10 and then another query on all views together but that doesn't sound 
very elegant and would be a real memory hog for a large number of days.

Any better ideas?

Thanks

Frank

um, this was probably unintelligible. this is the table:

+----------------------------------+----------------------------------+-------+
|              Field               |              Type                | Length|
+----------------------------------+----------------------------------+-------+
| source_numeric                   | int8 not null                    |     8 |
| destination_numeric              | int8 not null                    |     8 |
| source                           | text not null                    |   var |
| destination                      | text not null                    |   var |
| bytes                            | int8 not null                    |     8 |
| date                             | datetime                         |     8 |
+----------------------------------+----------------------------------+-------+

every hour, a set of rows is added to this table with the current timestamp on 
each row. i guess i need a function to extract the time from datetime. date_trunc
may be what i am looking for but i couldn't find information in the documentation
as to how to use these functions.


On Sat, Aug 28, 1999 at 03:35:07PM +0200, Frank Joerdens wrote:
> I'm not sure how to go about this: I want to find all rows with a timestamp 
> between, say 6 a.m. and 10 p.m. for any number of days. The column format is
> datetime. How do I extract the 'time of the day' information from this
> column? What I can think of is to create a view for every single day where datetime
> is > 6 and < 10 and then another query on all views together but that doesn't sound 
> very elegant and would be a real memory hog for a large number of days.
> 
> Any better ideas?
> 
> Thanks
> 
> Frank
> 
> 
> ************

Frank,
Use the date_part function to extract the hour and then
find the records which match.

E.g. select id,date_part('hour', mydate) from table1 where date_part('hour', mydate) >= 6 and date_part('hour', mydate)
<=22; 

Troy


>
> I'm not sure how to go about this: I want to find all rows with a timestamp
> between, say 6 a.m. and 10 p.m. for any number of days. The column format is
> datetime. How do I extract the 'time of the day' information from this
> column? What I can think of is to create a view for every single day where datetime
> is > 6 and < 10 and then another query on all views together but that doesn't sound
> very elegant and would be a real memory hog for a large number of days.
>
> Any better ideas?
>
> Thanks
>
> Frank
>
>
> ************
>
>

Try this:
select extract(year from date) from tablename;
select extract(month from date) from tablename;
select extract(day from date) from tablename;
select extract(hour from date) from tablename;
select extract(minute from date) from tablename;
select extract(minute from date) from tablename;
select extract(second from date) from tablename;

José

Frank Joerdens ha scritto:

> um, this was probably unintelligible. this is the table:
>
> +----------------------------------+----------------------------------+-------+
> |              Field               |              Type                | Length|
> +----------------------------------+----------------------------------+-------+
> | source_numeric                   | int8 not null                    |     8 |
> | destination_numeric              | int8 not null                    |     8 |
> | source                           | text not null                    |   var |
> | destination                      | text not null                    |   var |
> | bytes                            | int8 not null                    |     8 |
> | date                             | datetime                         |     8 |
> +----------------------------------+----------------------------------+-------+
>
> every hour, a set of rows is added to this table with the current timestamp on
> each row. i guess i need a function to extract the time from datetime. date_trunc
> may be what i am looking for but i couldn't find information in the documentation
> as to how to use these functions.
>
> On Sat, Aug 28, 1999 at 03:35:07PM +0200, Frank Joerdens wrote:
> > I'm not sure how to go about this: I want to find all rows with a timestamp
> > between, say 6 a.m. and 10 p.m. for any number of days. The column format is
> > datetime. How do I extract the 'time of the day' information from this
> > column? What I can think of is to create a view for every single day where datetime
> > is > 6 and < 10 and then another query on all views together but that doesn't sound
> > very elegant and would be a real memory hog for a large number of days.
> >
> > Any better ideas?
> >
> > Thanks
> >
> > Frank
> >
> >
> > ************
>
> ************