query-optimization

I have simple article application with three tables: article id, title, body, user_id comment id, article_id, user_id, body user id, username On the landing page, I want to show the latest article titles with the author name and total numbers of comments of the article. The main problem is how to get total numbers of comments of the article,I did not get it right. I should get the following output: title username total_comments article 2 user2 0 article 1 user1 2 In my real application, I added a column in article table for total number of comments to the article. this column is updated when a

Having a situation similar to the following example: 1 parent entity Employee having 2 child collections: Addresses and Phones I need to retrieve in a single roundtrip all employees with their Addresses and Phones initialized and also cache the query that achieves that in level 2 cache using Cacheable() . Using: var baseQuery = session .Query<Employee>() .Cacheable(); baseQuery .FetchMany(e => e.Addresses) .ToFuture(); var list = baseQuery .FetchMany(e => e.Phones) .ToFuture() .ToList(); should work, but I get the following exception: NHibernate.PropertyAccessException Message: Exception

I am trying to run this query on http://dbpedia.org/sparql but I get an error that my query is too expensive. When I run the query trough http://dbpedia.org/snorql/ I get: The estimated execution time 25012730 (sec) exceeds the limit of 1500 (sec) ... When running the query through my python script using SPARQLWrapper I simply get an HTTP 500. I figure I need to do something to optimize my SPARQL query. I need the data for iterating over educational institutions and importing it in to a local database, maybe I am using SPARQL wrong and should do this in a fundamentally different way. Hope

I need some help writing/optimizing a query to retrieve the latest version of each row by type and performing some calculations depending on the type. I think would be best if I illustrate it with an example. Given the following dataset: +-------+-------------------+---------------------+-------------+---------------------+--------+----------+ | id | event_type | event_timestamp | message_id | sent_at | status | rate | +-------+-------------------+---------------------+-------------+---------------------+--------+----------+ | 1 | create | 2016-11-25 09:17:48 | 1 | 2016-11-25 09:17:48 | 0 | 0

I have a table which keeps parent-child-relations between items. Those can be changed over time, and it is necessary to keep a complete history so that I can query how the relations were at any time. The table is something like this (I removed some columns and the primary key etc. to reduce noise): CREATE TABLE [tblRelation]( [dtCreated] [datetime] NOT NULL, [uidNode] [uniqueidentifier] NOT NULL, [uidParentNode] [uniqueidentifier] NOT NULL ) My query to get the relations at a specific time is like this (assume @dt is a datetime with the desired date): SELECT * FROM ( SELECT ROW_NUMBER() OVER