Re: Fixing faulty dates - select on day part of a date field

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