Thread: Fixing faulty dates - select on day part of a date field
Hi all, I've got a problem with dates on one of my tables. I've been inserting dates in the format 'dd/mm/ccyy' which for the days 13-31 for each month worked fine. The problem I have is that for the days 01-12 for each month, the date was interpretted as 'mm/dd/ccyy'. Now I know about it I need to fix it. Two questions. 1) how can I select on part of a date? I need to select all records where the day is not > 12. 2) can I do this in a single update, i.e. can I do something around update calls set xdate = ???? where ??????; -- Gary Stainburn This email does not contain private or confidential material as it may be snooped on by interested government parties for unknown and undisclosed purposes - Regulation of Investigatory Powers Act, 2000
Hi
1. You could use date_part(). Try these things
select date_part('day', now());select date_part('month', now());select date_part('year', now());
2. Yeah, should be able to do it in one update
Regards,
Patrik Kudo
On Thu, 29 Nov 2001, Gary Stainburn wrote:
> Hi all,
>
> I've got a problem with dates on one of my tables. I've been inserting dates
> in the format 'dd/mm/ccyy' which for the days 13-31 for each month worked
> fine.
>
> The problem I have is that for the days 01-12 for each month, the date was
> interpretted as 'mm/dd/ccyy'. Now I know about it I need to fix it.
>
> Two questions.
>
> 1) how can I select on part of a date? I need to select all records where
> the day is not > 12.
> 2) can I do this in a single update, i.e. can I do something around
>
> update calls set xdate = ???? where ??????;
>
> --
> Gary Stainburn
>
> This email does not contain private or confidential material as it
> may be snooped on by interested government parties for unknown
> and undisclosed purposes - Regulation of Investigatory Powers Act, 2000
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
>
> http://www.postgresql.org/users-lounge/docs/faq.html
>
On Thu, 2001-11-29 at 12:31, Gary Stainburn wrote:
> I've got a problem with dates on one of my tables. I've been inserting dates
> in the format 'dd/mm/ccyy' which for the days 13-31 for each month worked
> fine.
>
> The problem I have is that for the days 01-12 for each month, the date was
> interpretted as 'mm/dd/ccyy'. Now I know about it I need to fix it.
>
> Two questions.
>
> 1) how can I select on part of a date? I need to select all records where
> the day is not > 12.
select date_part('part', attribute)
where part is one of week, day, year ans so on
standards compliant way is
select extract(part from attribute)
so:
select * from table where date_part('day', attribute) < 13;
> 2) can I do this in a single update, i.e. can I do something around
>
> update calls set xdate = ???? where ??????;
What exactly do you want to achieve?
Markus Bertheau
On Thursday 29 November 2001 12:06 pm, Markus Bertheau wrote:
> On Thu, 2001-11-29 at 12:31, Gary Stainburn wrote:
> > I've got a problem with dates on one of my tables. I've been inserting
> > dates in the format 'dd/mm/ccyy' which for the days 13-31 for each month
> > worked fine.
> >
> > The problem I have is that for the days 01-12 for each month, the date
> > was interpretted as 'mm/dd/ccyy'. Now I know about it I need to fix it.
> >
> > Two questions.
> >
> > 1) how can I select on part of a date? I need to select all records
> > where the day is not > 12.
>
> select date_part('part', attribute)
>
> where part is one of week, day, year ans so on
>
> standards compliant way is
>
> select extract(part from attribute)
>
> so:
>
> select * from table where date_part('day', attribute) < 13;
>
> > 2) can I do this in a single update, i.e. can I do something around
> >
> > update calls set xdate = ???? where ??????;
>
> What exactly do you want to achieve?
Thanks for the information. Basically what I want to be able to do is
correct the dates that are wrong by swapping the day and month parts.
For example, a date entered as 23/11/2000 is correctly stored as 2000/11/23
while a date entered as 07/11/2000 (7th Nov 2000) is incorrectly stored as
2000/07/11. I need to be able to access it using the select you gave above,
and then re-store the date as 2000/11/07.
something like:
update calls set date_part('day',xdate) = date_part('month',xdate), date_part('month',xdate) =
date_part('day',xdate) where date_part('day',xdate) < 13 and xdate < '2001/11/08';
(2001/11/08 is when I found/fixed the insert problem)
>
> Markus Bertheau
--
Gary Stainburn
This email does not contain private or confidential material as it
may be snooped on by interested government parties for unknown
and undisclosed purposes - Regulation of Investigatory Powers Act, 2000
On Thu, 2001-11-29 at 15:00, Gary Stainburn wrote:
> On Thursday 29 November 2001 12:06 pm, Markus Bertheau wrote:
> > On Thu, 2001-11-29 at 12:31, Gary Stainburn wrote:
> > > I've got a problem with dates on one of my tables. I've been inserting
> > > dates in the format 'dd/mm/ccyy' which for the days 13-31 for each month
> > > worked fine.
> > >
> > > The problem I have is that for the days 01-12 for each month, the date
> > > was interpretted as 'mm/dd/ccyy'. Now I know about it I need to fix it.
> > >
> > > Two questions.
> > >
> > > 1) how can I select on part of a date? I need to select all records
> > > where the day is not > 12.
> >
> > select date_part('part', attribute)
> >
> > where part is one of week, day, year ans so on
> >
> > standards compliant way is
> >
> > select extract(part from attribute)
> >
> > so:
> >
> > select * from table where date_part('day', attribute) < 13;
> >
> > > 2) can I do this in a single update, i.e. can I do something around
> > >
> > > update calls set xdate = ???? where ??????;
> >
> > What exactly do you want to achieve?
>
> Thanks for the information. Basically what I want to be able to do is
> correct the dates that are wrong by swapping the day and month parts.
>
> For example, a date entered as 23/11/2000 is correctly stored as 2000/11/23
> while a date entered as 07/11/2000 (7th Nov 2000) is incorrectly stored as
> 2000/07/11. I need to be able to access it using the select you gave above,
> and then re-store the date as 2000/11/07.
>
> something like:
>
> update calls set date_part('day',xdate) = date_part('month',xdate),
> date_part('month',xdate) = date_part('day',xdate)
> where date_part('day',xdate) < 13 and xdate < '2001/11/08';
>
> (2001/11/08 is when I found/fixed the insert problem)
update calls set xdate = date_part('year', data) || '-' ||
date_part('day', data) || '-' || date_part('month', data) where ...;
|| is a string concatenation operator.
The query above swaps month and day.
The query only handles dates. If xdate also contains time information
you have to add it.
Markus Bertheau
> update calls set date_part('day',xdate) =
> date_part('month',xdate),
> date_part('month',xdate) = date_part('day',xdate)
> where date_part('day',xdate) < 13 and xdate < '2001/11/08';
>
> (2001/11/08 is when I found/fixed the insert problem)
You should always use the ISO date format - it avoids all these problems,
and is unambiguous. It is: YYYY-MM-DD
Chris
Hi Chris,
I do now, hence the explicit date check of 2001/11/08 which is when I fixed
the script. BTW, it doesn't seem to matter whether I use '/' or '-'.
Gary
On Friday 30 November 2001 1:34 am, Christopher Kings-Lynne wrote:
> > update calls set date_part('day',xdate) =
> > date_part('month',xdate),
> > date_part('month',xdate) = date_part('day',xdate)
> > where date_part('day',xdate) < 13 and xdate < '2001/11/08';
> >
> > (2001/11/08 is when I found/fixed the insert problem)
>
> You should always use the ISO date format - it avoids all these problems,
> and is unambiguous. It is: YYYY-MM-DD
>
> Chris
>
>
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Gary Stainburn
This email does not contain private or confidential material as it
may be snooped on by interested government parties for unknown
and undisclosed purposes - Regulation of Investigatory Powers Act, 2000