I'm building a little Sinatra web app at the moment and having problems understanding queries with DataMapper.
I have a field in my database which I've called date, I'd love to query this and only return records from this current month.
I've tried this:
query = "2012-11"
#trips = Trip.all(:date.like => '%query%')
Which doesn't seem to work, I'm hoping someone might spot my error and give me some guidance! Hope someone can help, thanks for taking the time to read.
Dave
Provide a range instead:
#trips = Trip.all(:date => (query..query))
I'd also fix your date format and provide month, day and year.
you could try this:
require 'date'
date_c = Date.today
next_y, next_m = date_c.month == 12 ?
[date_c.year+1, 1] : [date_c.year, date_c.month+1]
date_a = Date.new(date_c.year, date_c.month)
date_z = Date.new(next_y, next_m)
Trip.all :date => date_a..date_z
this will return current month entries
Related
I am building a simple app and I want to show some simple statistics to admins. I want to know is it possible to get the array of counts of objects from database that were created on the same date using datamapper or do I have to manually go through records and count them?
Objects have created_at attribute.
So i managed to solve it, I dont know if it is the right way but it works
days = Array.new
count = Array.new
photos_per_day = Photo.aggregate(:all.count, :upload_date)
photos_per_day.each do |ppd|
count.push(ppd[0])
days.push(ppd[1].day.to_s + " " + Date::MONTHNAMES[photo[1].month])
end
{:days => days, :count => count}.to_json
try this out:-
suppose you want to count users created on specific date.
User.group('date(created_at)').count
=> {"2013-05-20"=>66,
"2013-05-07"=>46,
"2013-05-17"=>9,
"2013-05-13"=>28,
"2013-05-22"=>22,
"2013-05-15"=>43,
"2013-05-08"=>32,
"2013-06-12"=>2,
"2013-05-28"=>22,
"2013-05-16"=>35,
"2013-05-09"=>33,
"2013-05-10"=>132,
"2013-05-21"=>5,
"2013-05-14"=>38,
"2013-05-11"=>4}
I run the following in Rails:
coe = trackers.where(:trackable_type => "Mailing").count(:group => 'DATE(created_at)')
which returns a hash with the items nicely grouped.
However I want to group not by date only by date but by the hour, but not the minutes or seconds.
How can I run this query so all the heavy lifting is done by Postgresql and not convert after I get the data set back?
My mistake I want to group by Date and Hour. Sorry for the confusion.
It sounds like you want the date_trunc() function:
http://www.postgresql.org/docs/current/interactive/functions-datetime.html#FUNCTIONS-DATETIME-TABLE
I want to group not by date but by the hour, but not the minutes or
seconds.
Bold emphasis mine.
So date_trunc()is probably not what you want, but EXTRACT or date_part():
coe = trackers.where(:trackable_type => "Mailing").count(:group => 'EXTRACT (hour FROM created_at)')
I have a table in Mongo. One of the fields is a DateTime. I would like to be able to get all of the records that are only for a single day (i.e. 9/3/2011).
If I do something like this:
var list = (from c in col
where c.PublishDate == DateTime.Now
select c).ToList();
Then it doesn't work because it is using the time in the comparison. Normally I would just compare the ToShortDateString() but NoRM does not allow me to use this.
Thoughts?
David
The best way to handle this is normally to calculate the start datetime and end datetime for the date in question and then query for values in that range.
var start = DateTime.Now.Date;
var end = start.AddDays(1);
...
But you'd also be well advised to switch to the official C# driver now. You should also use UTC datetimes in your database (but that gets more complicated).
Is there any easy way to compare dates, that ignores year, using Linq and the Entity Framework?
Say I have the following
var result = context.SomeEntity.Where(e => e.SomeDate > startDate);
This is assuming that SomeDate and startDate are .NET DateTime's.
What I would like to do is compare these dates without comparing year. SomeDate can be any year. Is there any easy way to do this? The only way I could think of would be to use the following:
var result = context.SomeEntity(e =>
e.SomeDate.Month > startDate.Month ||
(e.SomeDate.Month == startDate.Month && e.SomeDate.Day >= startDate));
This method quickly gets more complicated if I am looking to have an endDate as well, as I will have to do things like take account for when the start date is at the end of the year and the end date is at the beginning.
Is there any easy way to go about this?
Update:
I ended up just going about it the way I had initially thought in the post... a heck of a lot of code for something conceptually simple. Basically just had to find if a date fell within a range, ignoring year, and looping the calendar if startDate > endDate If anyone knows an easier way, please post as I am still interested.
If you really need to compare only dates (not times) then DateTime.DayOfYear property might help. But you should be careful regarding leap years in this case. Other of this I cannot imagine anything more simple than your approach with comparing months and days.
If all you care about is that this method will become more complicated after introducing second comparison then simple method extraction should help.
Another approach might be creating an extension method which will return a number applicable for your comparison. For example let's call this method GetYearIgnoringOrdinal():
public static int GetYearIgnoringOrdinal(this DateTime date)
{
return date.Month*100 + date.Day;
}
And then use it like this:
var result = context.SomeEntity.Where(e => e.SomeDate.GetYearIgnoringOrdinal() > startDate.GetYearIgnoringOrdinal());
Slightly simpler looking way
var result = context.SomeEntity(e =>
e.SomeDate.Month * 100 + e.SomeDate.Day > startDate.Month * 100 + startDate.Day
);
You could also create a user defined function (assuming SQL server is used) and that function can be used in the query.
I have a table with many anniversaries : Date + Name.
I want to display the next anniversary and the one after with Linq.
How can i build the query ?
I use EF
Thanks
John
Just order by date and then use the .Take(n) functionality
Example with a list of some objects assuming you want to order by Date then Name:
List<Anniversaries> annivDates = GetAnnivDates();
List<Anniversaries> recentAnniv = annivDates.OrderBy(d => d.Date).ThenBy(d => d.Name).Take(2).ToList();
If the anniversaries are stored in regular DateTime structs, they may have the 'wrong' year set (i.e. wedding or birth year). I suggest writing a function which calculates the next date for an anniversary (based on the current day) like:
static DateTime CalcNext(DateTime anniversary) {
DateTime newDate = new DateTime(DateTime.Now.Year, anniversary.Month, anniversary.Day);
if (newDate < DateTime.Now.Date)
newDate = newDate.AddYear(1);
return newDate;
}
Then you proceed with sorting the dates and taking the first two values like described in the other postings:
(from e in anniversaries orderby CalcNext(e.Date) select e).Take(2)