Given this class
class User < Sequel::Model
one_to_many :rounds, order: :date
end
What I'm trying to do is sort by descending date.
I tried this like ActiveRecord supports, but that is not the way to go.
one_to_many :rounds, order: date: :desc
One solution is to create a dataset method but I feel there must be a better way to do this.
The way to do this is to use one of the many "builders" that come with Sequel.
This time namely the Sequel.desc one.
one_to_many :rounds, order: Sequel.desc(:date)
Related
Let's say a supermarket has one table with statistical revenue data by business day. In a second table they want to try out different variations of these data, f.e. less bakery revenue at 1st January, one more public holiday or maybe opening on sundays.
I do not want to duplicate the whole revenue data of a year or more for just a few variations. Additionally it should be easily possible to show the diff between the base table and one alternative scenario.
To make it a little more clear, I created a demo case at SQLFiddle. SUPERMARKET_DAYS is the table with the base revenue data. ALTERNATIVES are the variations/alternatives or scenarios (however you want to name it) and ALTERNATIVE_DAYS is a table with a similar structure as the first one and holds the concrete changes.
Example at SQLFiddle
SUPERMARKET_DAYS
(
ID,
DAY,
NUM_CUSTOMERS,
NUM_VISITORS,
REVENUE_BAKERY,
REVENUE_BEVERAGE,
REVENUE_CANNED,
REVENUE_DAIRY,
REVENUE_DRY,
REVENUE_FROZEN,
REVENUE_MEAT,
REVENUE_CLEAN,
REVENUE_PERSONAL_CARE,
REVENUE_PAPER,
REVENUE_OTHER
)
ALTERNATIVES
(
ID,
TITLE
)
ALTERNATIVE_DAYS
(
ID,
DAY,
NUM_CUSTOMERS,
NUM_VISITORS,
REVENUE_BAKERY,
REVENUE_BEVERAGE,
REVENUE_CANNED,
REVENUE_DAIRY,
REVENUE_DRY,
REVENUE_FROZEN,
REVENUE_MEAT,
REVENUE_CLEAN,
REVENUE_PERSONAL_CARE,
REVENUE_PAPER,
REVENUE_OTHER
)
I do not even know, if this schema design makes any sense but it illustrates the problem.
How would you store this kind of data?
I thought about something like a versioning table but this does not really solve my problem.
I could merge both tables inside of my java code.
Is there something like the MERGE functionality for views?
I would really be grateful for every kind of idea or the correct keyword for my own investigations. This problem should already exist but I didn't find much to solve it, so I maybe did not search with the correct terms.
Thank you everybody!
I am implementing a GWT CellTable with paging and sorting by multiple columns dynamically.
The basics can be found in the CellTable Developer's Guide.
However, the dynamic example does not tell how to find out by which column the user wants to sort (it simply sorts by the 'name' column). That's not enough in my case, as I want to allow the user to sort by different columns.
The only solution I could think of, which is not very elegant, is to keep track of which column is sorted in ascending order or not (using table.getColumnSortList(indexOfColumn).isAscending()) and then figuring out which one has been clicked by comparing the values for each column (the one that changed is probably what the user clicked).
This involves keeping information in my classes that should be available somewhere in the CellTable! But I can't find that information!
Thanks for any help.
I found the answer. As explained in the javadocs for com.google.gwt.user.cellview.client.ColumnSortList:
An ordered list containing the sort history of Columns in a table. The 0th item is the ColumnSortInfo of the most recently sorted column.
So, to know which column was last sorted by, you simply do:
ColumnSortInfo info = table.getColumnSortList().get(0);
Column<Type> sortByColumn = info.getColumn();
I am using Mongoid to store a series of geocoded listings. These listings need to be sorted by price and proximity. The price of every listing is a field in the database whereas distance is a dynamic property that is unique for every user.
class Listing
include Mongoid::Document
field :price
def distance
get_distance(current_user.location,coordinates)
end
end
How can I sort these documents by distance? I tried #listing.desc(:distance) and that didn't work.
The short (and unhelpful) answer is: you can't.
Mongoid does have the ability to query based on 2d co-ordinates though, then you could update your controller to do something like this:
#listings = Listing.near(current_user.location)
Which I believe will return your listings in order of distance.
On a side note, I noticed that your Listing model is referring to your current_user object, which kinda breaks the MVC architecture, since your models shouldn't know anything about the current session.
I have a REST service that allows people to put in a course title as part of the query to get scores, but, sometimes they may want to get a group, such as Calculus% for Calc 1, 2 and 3.
But, what is the best way to give them an option that makes sense?
For example, I have http://localhost/myrest/any/any/Calculus III
where the first two parameters are student id and some grade category.
I don't think having http://localhost/myrest/any/any/contains/Calculus III is a good use as then I will need to force them to use equals if that is what they are looking for.
Another option is http://localhost/myrest/any/any/Calculus% or http://localhost/myrest/any/any/%Calc% is another option, but then you have removed the option to easily use % as an allowed character.
So, to give additional filtering options in a REST URL, what is the best (defined as simplest/most intuitive for the user) way to allow contains or starts with.
In your system, would the following query list all subjects in the grade category?
http://localhost/myrest/any/any/
If yes, then one option you can consider is extracting the non-exact subject name into a GET parameter. Thus without breaking the current logic where having a full name of the subject in the URL provides the score for that subject, you'd also have the ability to filter the list of subjects within the same grade category by means of the GET parameter.
For example:
http://localhost/myrest/any/any/?search=Calculus*
... could provide a result like this:
<subjects>
<subject uri="/myrest/any/any/Calculus%20I">A</subject>
<subject uri="/myrest/any/any/Calculus%20II">B</subject>
<subject uri="/myrest/any/any/Calculus%20III">C</subject>
</subjects>
i am wondering how can i select specific number of child objects instead of taking them all with include?
lets say i have object 'Group' and i need to select last ten students that joined the group.
When i use '.Include("Students"), EF includes all students. I was trying to use Take(10), but i am pretty new to EF and programming as well, so i couldn't figure it out.
Any suggestions?
UPDATED:
ok, i have Group object already retrieved from db like this:
Group group = db.Groups.FirstOrDefault(x=>x.GroupId == id)
I know that i can add Include("Students") statement, but that would bring ALL students, and their number could be quite big whether i need only freshest 10 students. Can i do something like this: var groupWithStudents = group.Students.OrderByDescending(//...).Take(10);?
The problem with this is that Take<> no longer appears in intellisense. Is this clear enough? Thanks for responses
I believe Take(10) would be correct.
var Students= (from c in Groups
orderby c.DateAdded descending
select c).Take(10);
My experience with Take though is that it generates some awful sql.
EDIT:
see if this blog post helps, it talks of conditional includes.
http://blogs.msdn.com/b/alexj/archive/2009/10/13/tip-37-how-to-do-a-conditional-include.aspx
Couldn't make Gratzy's suggestion with conditional include work... and found the solution here: http://msdn.microsoft.com/en-us/library/bb896249.aspx
Query would look like this:
group.Students.Attach(group.Students
.CreateSourceQuery()
.OrderByDescending(x=>x.JoinDate)
.Take(10));
This is exactly what i was looking for!
Thanks for all responses anyway!