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• Creating a multi-row "table" as part of a SELECT

  - by Chad Birch

  I'm not really sure how to describe my question (thus the awful title), but it's related to this recent question. The problem would be easily solved if there was some way for me to create a "table" with 4 rows as part of my SELECT (to use with NOT IN or MINUS). What I mean is, I can do this: SELECT 1, 2, 3, 4; And will receive one row from the database: | 1 | 2 | 3 | 4 | But is there any way to receive the following (without using UNION, I don't really want a query that's potentially thousands of lines long with a long list)? | 1 | | 2 | | 3 | | 4 |

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• Oracle ORA-01795 error in Rails

  - by Cyborgo

  Hi, I am using Oracle as database for my Rails applications and have got some pretty intense tables. I'm trying to find the particular entries using a query like this Author.all( :conditions => { :name => names } ) I have been working SQlite all along and just migrated to Oracle which complains that IN clause has more than 1000 entries. Obvious workaround would be to break it into subclauses for which I need to write some raw sql queries. Is there anything in Rails that facilitate this?

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• In Django, using __init__() method of non-abstract parent model to record class name of child model

  - by k-g-f

  In my Django project, I have a non-abstract parent model defined as follows: class Parent(models.Model): classType = models.CharField(editable=False,max_length=50) and, say, two children models defined as follows: class ChildA(Parent): parent = models.OneToOneField(Parent,parent_link=True) class ChildB(Parent): parent = models.OneToOneField(Parent,parent_link=True) Each time I create an instance of ChildA or of ChildB, I'd like the classType attribute to be set to the strings "ChildA" or "ChildB" respectively. What I have done is added an _ _ init_ _() method to Parent as follows: class Parent(models.Model): classType = models.CharField(editable=False,max_length=50) def __init__(self,*args,**kwargs): super(Parent,self).__init__(*args,**kwargs) self.classType = self.__class__.__name__ Is there a better way to implement and achieve my desired result? One downside of this implementation is that when I have an instance of the Parent, say "parent", and I want to get the type of the child object linked with "parent", calling "parent.classType" gives me "Parent". In order to get the appropriate "ChildA" or "ChildB" value, I need to write a "_getClassType()" method to wrap a custom sql query.

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• Retain Site Background and Switch Pages?

  - by yar

  I was about to redo a Rails site today using AJAX so that the background could remain in place. Then I thought, "that would be exactly like using frames," and then I thought about SEO consequences and I dropped the idea entirely and took a look around the Web. It turns out that few sites -- except for Google itself, which has the link bar at the top -- are doing this. It doesn't look impossible to do, but it's not exactly easy. Aside from Ajaxing, you have to think about updating the query-string and having SEO-friendly links (that actually don't work, but rather make background requests via Javascript). Will any of the new technologies -- HTML5, perhaps -- solve this problem and allow us to have a Web with background colors (and other static elements) that do not disappear momentarily between page refreshes? On the other hand, why are few devs doing this with current technologies? Is it just not a big deal, too complicated to implement, or....?

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• MySQL UPDATE WHERE IN for each listed value separately?

  - by Tom

  Hi, I've got the following type of SQL: UPDATE photo AS f LEFT JOIN car AS c ON f.car_id=c.car_id SET f.photo_status=1 , c.photo_count=c.photo_count+1 WHERE f.photo_id IN ($ids) Basically, two tables (car & photo) are related. The list in $ids contains unique photo ids, such as (34, 87, 98, 12). With the query, I'm setting the status of each photo in that list to "1" in the photo table and simultaneously incrementing the photo count in the car table for the car at hand. It works but there's one snag: Because the list can contain multiple photo ids that relate to the same car, the photo count only ever gets incremented once. If the list had 10 photos associated with the same car, photo_count would become 1 .... whereas I'd like to increment it to 10. Is there a way to make the incrementation occur for each photo individually through the join, as opposed to MySQL overthinking it for me? I hope the above makes sense. Thanks.

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• How to convet DataTable to List on runtype with out existin class property [closed]

  - by shamim

  Work on VS2010 C#,Have one DataTable ,want to convert this DataTable to List Suppose: Table dt; On run time want to create similar field from a datatable and fill fields in List.There is no existing class for list properties. ListName=TableName List property name=Table column name List Property type=Table column type List items=Table rows Note: Recently work on EF.To fullfill my project requirement, need to give flexibility to use to input and execute ESQL at runtime .I don’t want to put this execute result on datatable or List ,want to put this result on list. List has no existing class and property,don’t want to convert DataTable on list Type:DataRow If have any query please ask,Thanks in advanced.

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• Use AJAX to check for a new message

  - by Luke

  Quite simply, I need to alert the end user when they have a new private message. From a combination of research and other opinion, I realise I need to use AJAX for this. The mysql query would be SELECT id FROM tbl_messages WHERE to_viewed = 1 So when someone sends a message, I want an alert to popup on the screen to inform the user without a page reload. I have absolutely no idea what I am doing, but know what I want. Really need help with this, AJAX is definitely something I want to improve as it opens up greater possibilities! Thanks

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• is NATURAL JOIN any better than SELECT FROM WHERE in terms of performance ?

  - by ashy_32bit

  Today I got into a debate with my project manager about Cartesian products. He says a 'natural join' is somehow much better than using 'select from where' because the later cause the db engine to internally perform a Cartesian product but the former uses another approach that prevents this. As far as I know, the natural join syntax is not any different in anyway than 'select from where' in terms of performance or meaning, I mean you can use either based on your taste. SELECT * FROM table1,table2 WHERE table1.id=table2.id SELECT * FROM table1 NATURAL JOIN table2 please elaborate about the first query causing a Cartesian product but the second one being somehow more smart

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• Incrementing through mysql PHP

  - by Rawdon

  I am looking at try to increment and decrement by three records through a table and present those records. Say if the id '4' is currently active. I want the to be display the ID's and category of 3.2.1 and 5.6.7 from an increment and decrement So far I have: $stmt = $db->query("SELECT id, category FROM test"); $stmt->execute(); while ($results = $stmt->fetch(PDO::FETCH_ASSOC)) { $current = $results['id']; $category = $results['category']; $next = array(array('slide_no' => $current, 'category' => $category)); } print_r($next); Now with this, I am getting back every row in the table. I'm now getting confused on how I could increment and decrement the records by 3 and make sure that the category will also increment correctly. Thank you very much.

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• How to map one class against multiple tables with SQLAlchemy?

  - by tote

  Lets say that I have a database structure with three tables that look like this: items - item_id - item_handle attributes - attribute_id - attribute_name item_attributes - item_attribute_id - item_id - attribute_id - attribute_value I would like to be able to do this in SQLAlchemy: item = Item('item1') item.foo = 'bar' session.add(item) session.commit() item1 = session.query(Item).filter_by(handle='item1').one() print item1.foo # => 'bar' I'm new to SQLAlchemy and I found this in the documentation (http://www.sqlalchemy.org/docs/05/mappers.html#mapping-a-class-against-multiple-tables): j = join(items, item_attributes, items.c.item_id == item_attributes.c.item_id). \ join(attributes, item_attributes.c.attribute_id == attributes.c.attribute_id) mapper(Item, j, properties={ 'item_id': [items.c.item_id, item_attributes.c.item_id], 'attribute_id': [item_attributes.c.attribute_id, attributes.c.attribute_id], }) It only adds item_id and attribute_id to Item and its not possible to add attributes to Item object. Is what I'm trying to achieve possible with SQLAlchemy? Is there a better way to structure the database to get the same behaviour of "dynamic columns"?

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• Considerations when porting a MS VC++ program (single machine) to a rocks cluster

  - by Mel

  I am trying to port a MS VC++ program to run on a rocks cluster! I am not very good with linux but I am eager to learn and I imagine porting it wouldn't be an impossible task for me. However, I do not understand how to take advantage of the cluster nodes. because it seems that the code execute only runs on the front end server (obviously). I have read a little about MPI and its seems like I should use MPI to comminicate between nodes. The program is currently written such that I have a main thread that synchronizes all worker threads. The main thread also recieves commands to manipulate the simulation or query its state. If the simulation is properly setup, communication between executing threads can be significantly minimized. What I don't understand is how do I start the process on the compute nodes and how do I handle failures in nodes? And maybe there should be other things I should also consider when porting my program to run in a cluster?

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• Why are my Lucene Document results empty?

  - by vegashacker

  I'm running a simple test--trying to index something and then search for it. I index a simple document, but then when a search for a string in it, I get back what looks to be an empty document (it has no fields). Lucene seems to be doing something, because if I search for a word that's not in the document, it returns 0 results. Any reason why Lucene would reliably return a document when it finds one that matches the given query, and yet that document has nothing in it? Thanks! PS: I'm actually running Lucandra (Lucene + Cassandra). That certainly may be a relevant detail, but not sure.

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• Finding employees specific to department in SQL SERVER 2000(SET BASED)

  - by xyz

  Suppose I have a table (tblEmp) whose structure is like as under Dept Emp d1 e1 d1 e2 d1 e3 d2 e4 d2 e5 d3 e6 If I need to bring the output as Dept DepartmentSpecificEmployees d1 e1,e2,e3 d2 e4,e5 d3 e6 I will write the query as select Dept, stuff((select Emp + ',' from tblEmp t2 where t1.Dept = t2.Dept for xml path(''),1,1,'')DepartmentSpecificEmployees from tblEmp t1 group by Dept But this will work in Sql Server 2005+. How can I achieve the same in Sql Server 2000 without any variable declaration or loop or cursor? If I use COALESCE as an alternative, then I need to use a variable which will defeat the purpose Please help

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• For LinqToSQL is 0 true or is 1 (for type Bit)?

  - by Vaccano

  I have a column of type Bit (called BBoolVal in this example). I have a LinqToSQL Statement Like this: var query = List<MyClass> myList = _ctx.DBList .Where(x => x.AGuidID == paramID) .Where(x => x.BBoolVal == false); When I look at the sql it ends up like this (I added the spacing and changed the names): SELECT [t0].[Id], [t0].[AGuidID], [t0].[OtherIDID], [t0].[TimeColumn], [t0].[BBoolVal], [t0].[MoreID] FROM [dbo].[MyTable] AS [t0] WHERE (NOT ([t0].[BBoolVal] = 1)) AND ([t0].[AGuidID] = @p0) Because my x.BBoolVal == false translates to [BBoolVal] == 1 I gather that false = 1 (and thus true = 0). I am asking because this seems a bit backwards to me. I am fine to accept it, I just want to be sure.

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• Most efficient way to Update with Linq2Sql

  - by pranay

  can I update my employee record as given in below function or i have to make query of employee collection first and than i update data public int updateEmployee(App3_EMPLOYEE employee) { DBContextDataContext db = new DBContextDataContext(); db.App3_EMPLOYEEs.Attach(employee); db.SubmitChanges(); return employee.PKEY; } or i have to do this public int updateEmployee(App3_EMPLOYEE employee) { DBContextDataContext db = new DBContextDataContext(); App3_EMPLOYEE emp = db.App3_EMPLOYEEs.Single(e => e.PKEY == employee.PKEY); db.App3_EMPLOYEEs.Attach(employee,emp); db.SubmitChanges(); return employee.PKEY; } But i dont want to use second option is there any efficient way to update data

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• C# performance of static string[] contains() (slooooow) vs. == operator

  - by Andrew White

  Hiya, Just a quick query: I had a piece of code which compared a string against a long list of values, e.g. if(str == "string1" || str = "string2" || str == "string3" || str = "string4". DoSomething(); And the interest of code clarity and maintainability I changed it to public static string[] strValues = { "String1", "String2", "String3", "String4"}; ... if(strValues.Contains(str) DoSomething(); Only to find the code execution time went from 2.5secs to 6.8secs (executed ca. 200,000 times). I certainly understand a slight performance trade off, but 300%? Anyway I could define the static strings differently to enhance performance? Cheers.

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• INSERT INTO othertbl SELECT * tbl

  - by Harry

  Current situation: INSERT INTO othertbl SELECT * FROM tbl WHERE id = '1' So i want to copy a record from tbl to othertbl. Both tables have an autoincremented unique index. Now the new record should have a new index, rather then the value of the index of the originating record else copying results in a index not unique error. A solution would be to not use the * but since these tables have quite some columns i really think it's getting ugly. So,.. is there a better way to copy a record which results in a new record in othertbl which has a new autoincremented index without having to write out all columns in the query and using a NULL value for the index. -hope it makes sense....-

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• WMI instrinsic events. Resources

  - by Nickolodeon

  Hi. I subscribe to usb inserted event like this select * FROM __INSTANCECREATIONEVENT WITHIN 3 WHERE TARGETINSTANCE ISA Win32_DiskDrive After inserting usb flash it blinks every 3 seconds. This is polling interval and intrinsic events work by polling object that's in query. Now, we know these types of events may be resource expensive. (Putting value greater then 3 sometimes chokes these events and client program doesn't get notified). Are there other ways to do that, so that usb doesn't get scanned all the time? May be there some extrinsic events available? Right now the only solution I see is to unsubscribe from event above once it trigerred and resubscribe to it in __INSTANCEDELETIONEVENT handler. Hm, althought deletionevent will also poll diskdrive controllers(

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• Optimizing MySQL queries with IN operator

  - by Arkadiusz Kondas

  I have a MySQL database with a fairly large table where the products are. Each of them has its own id and categoryId field where there is a category id belongs to this product. Now I have a query that pulls out products from given categories such as: SELECT * FROM products WHERE categoryId IN ( 1, 2, 3, 4, 5, 34, 6, 7, 8, 9, 10, 11, 12 ) Of course, come a WHERE clause and ORDER BY sort but not in this thing. Let's say that these products is 250k and the visits are over 100k per day. Under such conditions in the table slow_log registered weight of these queries with large generation time. Do you have any ideas how to optimize the given problem? Table engine is MyISAM.

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• Strange Locking Behaviour in SQL Server 2005

  - by SQL Learner

  Can anyone please tell me why does the following statement inside a given stored procedure returns repeated results even with locks on the rows used by the first SELECT statement? BEGIN TRANSACTION DECLARE @Temp TABLE ( ID INT ) INSERT INTO @Temp SELECT ID FROM SomeTable WITH (ROWLOCK, UPDLOCK, READPAST) WHERE SomeValue <= 10 INSERT INTO @Temp SELECT ID FROM SomeTable WITH (ROWLOCK, UPDLOCK, READPAST) WHERE SomeValue >= 5 SELECT * FROM @Temp COMMIT TRANSACTION Any values in SomeTable for which SomeValue is between 5 and 10 will be returned twice, even though they were locked in the first SELECT. I thought that locks were in place for the whole transaction, and so I wasn't expecting the query to return repeated results. Why is this happening?

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• Modifying SQL XML ?olumn

  - by Chinjoo

  I have an XML column in one of my table. For example I have an Employee table with following fields: Name (varhcar) | Address (XML) The Address field is having values like <Address> <Street></Street> <City></City> </Address> I have some n number of rows already in the table. Now I want to insert a new node - Country to all the rows in tha table. With default: <Country>IND</Country>. How can I write the query for this. I want all the existing data to be as it is with adding the country node to all the Address column XML.

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• Optimizing Solr for Sorting

  - by devinfoley

  I'm using Solr for a realtime search index. My dataset is about 60M large documents. Instead of sorting by relevance, I need to sort by time. Currently I'm using the sort flag in the query to sort by time. This works fine for specific searches, but when searches return large numbers of results, Solr has to take all of the resulting documents and sort them by time before returning. This is slow, and there has to be a better way. What is the better way?

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• replicating master tables mapping in transaction tables

  - by NoDisplay

  I have three master tables for location information Country {ID, Name} State {ID, Name, CountryID} City {ID, Name, StateID} Now I have one transcation table called Person which hold the person name and his location information. My Question is shall I have only CityID in the Person table like this: Person {ID, Name, CityID}' And have view of join query which give me detail like "Person{ID,Name,City,State,Country}" or Shall I replicate the mapping Person {ID, Name, CityID, StateID, CountryID} Please suggest which do you feel is to be selected and why? if there is any other option available, please suggest. Thanks in advance.

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• :from parameter in active record find not well designed?

  - by potlee

  i got this error: SQLite3::SQLException: no such column: apis.name: SELECT * FROM examples WHERE ("apis"."name" = 'deep') my code Api.find :all, :from => params[:table_name], :conditions => {:name => 'deep' } I need to make a back end rails application which will be used by a silverlight application. one of the requirements is to fetch simple data from the database. i need to be able to query different tables with the same code.(my app has 2000 tables!) i think it does not make sense for rails to put in "apis" in the WHERE clause. is there any speciic reason for this?

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• Weird error: [Semantical Error] line 0, col 75 near 'submit': Error: 'submit' is not defined.

  - by luxury

  My controller like: /** * @Route("/product/submit", name="product_submit") * @Template("GaorenVendorsBundle:Product:index.html.twig") */ public function submitAction() { $em = $this->getDoctrine()->getManager(); $uid = $this->getUser()->getId(); $em->getRepository( 'GaorenVendorsBundle:Product' )->updateStatus( $uid, Product::STATUS_FREE, Product::STATUS_PENDING ); return $this->redirect( $this->generateUrl( 'product' ) ); } and the repo like: class ProductRepository extends EntityRepository { public function updateStatus($uid, $status, $setter) { $st = $this->getEntityManager()->getRepository( 'GaorenVendorsBundle:Product' ) ->createQueryBuilder( 'p' ) ->update( 'GaorenVendorsBundle:Product', 'p' ) ->set( 'p.status', ':setter' ) ->where( 'p.status= :status AND p.user= :user' ) ->setParameters( array( 'user' => $uid, 'status' => $status, 'setter' => $setter ) ) ->getQuery() ->execute() return $st; } when request the "submit" action, it prompts me "[Semantical Error] line 0, col 75 near 'submit': Error: 'submit' is not defined. ". "submit" is nothing to do with DOCTRINE orm query, why it appears in the error? I just can't figure out.Anyone could tell me?

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