sql-order-by

I'm quite new to LINQ. Suppose that I had the following table: Incident ID DeviceID Time Info 1 1 5/2/2009 d 2 2 5/3/2009 c 3 2 5/4/2009 b 4 1 5/5/2009 a In LINQ, how could I write a query that finds the most recent and distinct (on Device ID) set of incidents? The result I'd like is this: ID DeviceID Time Info 3 2 5/4/2009 b 4 1 5/5/2009 a Do you have to create an IEqualityComparer to do this? You can get the most recent incidents for each device (this is how I understood your question) with: var query = incidents.GroupBy(incident => incident.DeviceID) .Select(g => g.OrderByDescending

Possible Duplicate: Why do results from a SQL query not come back in the order I expect? From reading 7.5 Sorting Rows and from issues I've seen with PostgreSQL, my impression is the following, but that section is not fully explicit, so I would be grateful if someone could verify: SELECT * FROM items; has no guaranteed order. SELECT * FROM items ORDER BY published_date ASC; guarantees that two items with different dates come in a given order, but does not guarantee that two items with the same date always come in the same order. SELECT * FROM items ORDER BY published_date ASC, id ASC; always

Is there a way to know if an IQueryable<T> has been ordered (using OrderBy or OrderbyDescending )? So I know whether to call OrderBy or ThenBy on the collection. IQueryable<Contact> contacts = Database.GetContacts(); I tried contacts is IOrderedQueryable<Contact> , but it's always true. Edit : I just changed my example, the previous one wasn't really showing my point. Assume that GetContacts uses Entity Framework and simply returns all the records of a table. Later on, I apply several functions to contacts , I have no knowledge of what those functions do. They can sort or filter the IQueryable

I'm creating a system in which users can store messages via PHP with a MySQL database, and I am using the MySQL AES_ENCRYPT function to encrypt the contents of these messages. Here is my posts table: CREATE TABLE IF NOT EXISTS `posts` ( `id` int(11) NOT NULL AUTO_INCREMENT, `user` int(11) DEFAULT NULL, `group` int(11) DEFAULT NULL, `body` varbinary(1000) NOT NULL, `ip` varchar(45) NOT NULL, `date` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, `replyto` int(11) DEFAULT NULL, PRIMARY KEY (`id`), KEY `replyto` (`replyto`), KEY `user` (`user`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT

I am building a Rails 3 app with a pretty standard message model. I would like to return the most recently created message records for each unique conversation_id. It seems like a fairly simple task, but I have not been able to code or find a working solution. Admittedly, I am not super SQL savvy either (as I have gotten by with mainly Active Record queries thus far). Here is what I'm trying to accomplish. Sample messages table: | id | sender_id | receiver_id | conversation_id | subject | body | created_at | | 1 | * | * | 1 | * | * | 16:01 | | 2 | * | * | 2 | * | * | 17:03 | | 3 | * | * | 1 |

Is it possible to order the results of a PostgreSQL query by a title field that contains characters like [](),; etc but do so ignoring these punctuation characters and sorting only by the text characters? I've read articles on changing the database collation or locale but have not found any clear instructions on how to do this on an existing database an on a per-column basis. Is this even possible? If you want to have this ordering in one particular query you can ORDER BY regexp_replace(title, '[^a-zA-Z]', '', 'g') It will delete all non A-Z from sting and order by resulting field. Erwin

I have a table with the fields CommonName and FirstName . Only either field has data, never both. Is there a way to order rows in an intersecting manner on SQL Server? Example: CommonName FirstName Bern Wade Ashley Boris Ayana I want records ordered like this: CommonName FirstName Ashley Ayana Bern Boris Wade Is this possible, and if so, how? Use a CASE statement to select the value for that row and ORDER BY that. ORDER BY CommonName + FirstName , with appropriate ISNULL(<column>, '') if they are nullable. ORDER BY CASE WHEN CommonName is null THEN FirstName ELSE CommonName END order by