[Qgis-user] Filter syntax for date fields

[Patrick Dunford]

Probaly as a workaround right now it looks like for my scenario the
simplest q&d option is to extract the date into separate y/m/d fields
stored as integers and run the filter against these. 

On Fri, 2017-10-20 at 10:25 +0200, Luigi Pirelli wrote:
> This could be related with a similar proble reported in
> https://issues.qgis.org/issues/16657 assigned to 3ndis (Denis) that
> will work on that (master and 2.18) on November during bugfix period.
> The parse is done QDateTime and is hard to match the exact QDateTime
> format. If it match, than the value is correctly used, otherwise the
> current time is used.
> 
> probably we need a more general way to parte datetime shared with
> editor delegate and functions.
> 
> you can do a workaround adding your custom function that instruct
> QDate to parse only Y
> 
> Luigi Pirelli
> 
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> 
> On 20 October 2017 at 04:30, Patrick Dunford <blackwhitekez at gmail.com
> > wrote:
> > I have a shapefile table with 300,000 records of polygons that I
> > want
> > to filter for display on the map canvas. I want to use the field
> > called
> > "date" which is defined as a Qdate in the fields list in the
> > shapefile's properties.
> > 
> > The question is how to put in the filter string in the correct
> > syntax
> > to give me for example all the records that are for the calendar
> > year
> > of 1984.
> > 
> > For example
> >  year("date") = 1984
> > will not work because it doesn't accept the year function from the
> > list
> > of functions that are available in other expression editors which
> > allow
> > a function list to be used.
> > 
> > In a previous version of this table I had it was actually quite
> > easy
> > because the dates were input as a string and the like operator
> > could be
> > used. It seems with a date that is actually defined as a date field
> > there is no obvious or easy way to input a range of dates (how do
> > you
> > put in a date constant) or use a function that will extract part of
> > a
> > date from a date field.
> > 
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