aggregate

composed_of in Rails - when to use it?

When should you use ActiveRecord's composed_of class method? ...

How to formulate a SQL Server indexed view that aggregates distinct values?

I have a schema that includes tables like the following (pseudo schema): TABLE ItemCollection { ItemCollectionId ...etc... } TABLE Item { ItemId, ItemCollectionId, ContributorId } I need to aggregate the number of distinct contributors per ItemCollectionId. This is possible with a query like: SELECT ItemCollectionI...

SQL Complex Select - Trouble forming query

I have three tables, Customers, Sales and Products. Sales links a CustomerID with a ProductID and has a SalesPrice. select Products.Category, AVG(SalePrice) from Sales inner join Products on Products.ProductID = Sales.ProductID group by Products.Category This lets me see the average price for all sales by category. However, I only ...

Server side aggregation using Spring MVC Controllers

Hi! We have a web site with multiple pages each with lot of AJAX calls. All the Ajax calls go to a data proxy layer written in Spring 3 MVC application. In order to reduce the load on the server we are planning to aggregate calls on the client and send to the proxy layer. For ex: we have two calls /controller1/action1 and /controlle...

Linq Aggregate function

I have a List like "test", "bla", "something", "else" But when I use the Aggrate on it and in the mean time call a function it seems to me that after 2 'iterations' the result of the first gets passed in? I am using it like : myList.Aggregate((current, next) => someMethod(current) + ", "+ someMethod(next)); and while I put a breakp...

Request for advice about class design, inheritance/aggregation

I have started writing my own WebDAV server class in .NET, and the first class I'm starting with is a WebDAVListener class, modelled after how the HttpListener class works. Since I don't want to reimplement the core http protocol handling, I will use HttpListener for all its worth, and thus I have a question. What would the suggested w...

Why do I need to explicitly specify all columns in a SQL "GROUP BY" clause - why not "GROUP BY *"?

This has always bothered me - why does the GROUP BY clause in a SQL statement require that I include all non-aggregate columns? These columns should be included by default - a kind of "GROUP BY *" - since I can't even run the query unless they're all included. Every column has to either be an aggregate or be specified in the "GROUP BY", ...

can I get count() and rows from one sql query in sql server?

I'd like to get the total count of results and top n rows of some query - is it possible in one statement? I'd expect the results as: count(..) column1 column2 125 some_value some_value 125 some_value some_value Thank you in advance! ...

How to transform one list to another semi-aggregated list via LINQ?

I'm a Linq beginner so just looking for someone to let me know if following is possible to implement with Linq and if so some pointers how it could be achieved. I want to transform one financial time series list into another where the second series list will be same length or shorter than the first list (usually it will be shorter, i.e....

SQL - How to join on similar (not exact) columns

I have two tables which get updated at almost the exact same time - I need to join on the datetime column. I've tried this: SELECT * FROM A, B WHERE ABS(DATEDIFF(second, A.Date_Time, B.Date_Time)) = ( SELECT MIN(ABS(DATEDIFF(second, A.Date_Time, B2.Date_Time))) FROM B AS B2 ) But it tells me: Multiple columns are specifie...

aggregate over several variables in r

Dear overflowers, I have a rather large dataset in a long format where I need to count the number of instances of the ID due to two different variables, A & B. E.g. The same person can be represented in multiple rows due to either A or B. What I need to do is to count the number of instances of ID which is not too hard, but also count t...

Performing Aggregate Functions on Multi-Million Row Tables

I'm having some serious performance issues with a multi-million row table that I feel I should be able to get results from fairly quick. Here's a run down of what I have, how I'm querying it, and how long it's taking: I'm running SQL Server 2008 Standard, so Partitioning isn't currently an option I'm attempting to aggregate all views f...

Maven - 'all' or 'parent' project for aggregation?

For educational purposes I have set up a project layout like so (flat in order to suite eclipse better): -product | |-parent |-core |-opt |-all Parent contains an aggregate project with core, opt and all. Core implements the mandatory part of the application. Opt is an optional part. All is supposed to combine core with opt, and ...

How to find the latest row for each group of data

Hi All, I have a tricky problem that I'm trying to find the most effective method to solve. Here's a simplified version of my View structure. Table: Audits AuditID | PublicationID | AuditEndDate | AuditStartDate 1 | 3 | 13/05/2010 | 01/01/2010 2 | 1 | 31/12/2009 | 01/10/2009 3 | 3 ...

How can I do this Aggrigate, group by, in query in LINQ?

Please do not give me a full working example, I want to know how this is done rather than to get some code I can copy paste This is the query I need, and can't for the life of me create it in LINQ. SELECT * FROM dbo.Schedules s, dbo.Videos v WHERE s.VideoID = v.ID AND s.ID IN ( SELECT MAX(ID) FROM dbo.Schedules WHERE ChannelID...

How do I aggregate activerecord model data for a specific time period?

I'm collecting data from a system every ~10s (this time difference varies due to communication time with networked devices). I'd like to calculate averages and sums of the stored values for this activerecord model on a daily basis. All records are stored in UTC. What's the correct way to sum and average values for, e.g., the previous ...

Delphi Clientdataset Lookup/Aggregate

Hi, I need a little help with ClientDatasets in Delphi. What I want to achieve is a grid showing customers, where one of the columns shows the number of orders for each customer. I put a ClientDataset on a form and load Customers.xml from Delphi demo-data. Another ClienDataset is loaded with orders.xml. Relatively simple, I can define ...

What's the most efficient query?

I have a table named Projects that has the following relationships: has many Contributions has many Payments In my result set, I need the following aggregate values: Number of unique contributors (DonorID on the Contribution table) Total contributed (SUM of Amount on Contribution table) Total paid (SUM of PaymentAmount on Payment tab...

Aggregate Functions on subsets of data based on current row values with SQL

Hopefully that title makes sense... Let's say I have an employee table: ID | Name | Title | Salary ---------------------------- 1 | Bob | Manager | 15285 2 | Joe | Worker | 10250 3 | Al | Worker | 11050 4 | Paul | Manager | 16025 5 | John | Worker | 10450 What I'd like to do is write a query that will give me the above ...

What method do you use to identify the Aggregate Roots in Domain Drive Design?

When applying Domain Driven Design to a project, how do you identify the Aggregate Roots? For example, in a standard E-Commerce website, you might say that the Order is one, and the User is the other. But what if your Users belong to a Company? Does that make your Company the aggregate root? I'm interested in hearing people's approache...