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  • Is it possible to dynamically discover tables in an Entity Framework model ?

    - by Scott Davies
    Hi, I have co-workers working on an Entity Framework model that changes structure (entities), over time as software development progresses. I've written some utilities that interact with the tables within the model, but I'd like to have the code dynamically discover the tables. Is there a way I can do this ? Perhaps with ADO.NET to get the table names and then store them in a collection ? Thanks, Scott

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  • KD-Trees and missing values (vector comparison)

    - by labratmatt
    I have a system that stores vectors and allows a user to find the n most similar vectors to the user's query vector. That is, a user submits a vector (I call it a query vector) and my system spits out "here are the n most similar vectors." I generate the similar vectors using a KD-Tree and everything works well, but I want to do more. I want to present a list of the n most similar vectors even if the user doesn't submit a complete vector (a vector with missing values). That is, if a user submits a vector with three dimensions, I still want to find the n nearest vectors (stored vectors are of 11 dimensions) I have stored. I have a couple of obvious solutions, but I'm not sure either one seem very good: Create multiple KD-Trees each built using the most popular subset of dimensions a user will search for. That is, if a user submits a query vector of thee dimensions, x, y, z, I match that query to my already built KD-Tree which only contains vectors of three dimensions, x, y, z. Ignore KD-Trees when a user submits a query vector with missing values and compare the query vector to the vectors (stored in a table in a DB) one by one using something like a dot product. This has to be a common problem, any suggestions? Thanks for the help.

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

    - by Jeremy Lew
    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 ItemCollectionId, COUNT(DISTINCT ContributorId) FROM Item GROUP BY ItemCollectionId I further want to pre-calculate this aggregation using an indexed (materialized) view. The DISTINCT prevents an index being placed on this view. Is there any way to reformulate this which will not violate SQL Server's indexed view constraints?

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  • How can I write this query in Django? (datetime)

    - by alex
    | time_before | datetime | YES | MUL | NULL | | | time_after | datetime | YES | MUL | NULL | | the_tag = Tag.objects.get(id=tag_id) Log.objects.filter(blah).extra(where=['last_updated >'+the_tag.time_before, 'last_updated' < the_tag.time_after]) Ok. Basically, I have an object that's called "the_tag". I want to select from Log where log.last_updated (which is a datetime field) is between the tag's time. But, I don't know how to write the last part of this Django query.

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  • SQL Select * from multiple tables

    - by zaf
    Using PHP/PDO is it possible to use a wildcard for the columns when a select is done on multiple tables and the returned array keys are fully qualified to avoid column name clash? example: SELECT * from table1, table2; gives: Array keys are 'table1.id', 'table2.id', 'table1.name' etc. I tried "SELECT table1.*,table2.* ..." but the returned array keys were not fully qualified so columns with the same name clashed and were overwritten.

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  • Join one row to multiple rows in another table

    - by Ghostrider
    I have a table to entities (lets call them people) and properties (one person can have an arbitrary number of properties). Ex: People Name Age -------- Jane 27 Joe 36 Jim 16 Properties Name Property ----------------- Jane Smart Jane Funny Jane Good-looking Joe Smart Joe Workaholic Jim Funny Jim Young I would like to write an efficient select that would select people based on age and return all or some of their properties. Ex: People older than 26 Name Properties Jane Smart, Funny, Good-looking Joe Smart, Workaholic It's also acceptable to return one of the properties and total property count. The query should be efficient: there are millions of rows in people table, hundreds of thousands of rows in properties table (so most people have no properties). There are hundreds of rows selected at a time. Is there any way to do it?

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  • How do views reduce code duplication?

    - by Debuger
    Hi! I read something like this about db views: Views are incredibly powerful and useful for one reason that stands out above all the other very good reasons. They reduce code duplication. That is, in most cases, the bottom line. If a query will be used in three or more places, then a view will drastically simplify your changes if the schema or query parameters change. I once had to edit 22 stored procedures to change some query logic. If the original architecture had utilized views, then I would have had only three changes. Can anyone explain to me how it works, and maybe give me some examples? Best regards!

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  • Creating SQL table using Dynamic variable name

    - by megatoast
    I want to create backup SQL tables using variable names. something along the lines of DECLARE @SQLTable Varchar(20) SET @SQLTable = 'SomeTableName' + ' ' + '20100526' SELECT * INTO quotename(@SQLTable) FROM SomeTableName but i'm getting Incorrect syntax near '@SQLTable'. It's just part of a small script for maintence so i don't have to worry about injections.

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  • Is it worth caching a Dictionary for foreign key values in ASP.net?

    - by user169867
    I have a Dictionary<int, string> cached (for 20 minutes) that has ~120 ID/Name pairs for a reference table. I iterate over this collection when populating dropdown lists and I'm pretty sure this is faster than querying the DB for the full list each time. My question is more about if it makes sense to use this cached dictionary when displaying records that have a foreign key into this reference table. Say this cached reference table is a EmployeeType table. If I were to query and display a list of employee names and types should I query for EmployeeName and EmployeeTypeID and use my cached dictionary to grab the EmployeeTypeIDs name as each record is displayed or is it faster to just have the DB grab the EmployeeName and JOIN to get the EmployeeType string bypassing the cached Dictionary all together. I know both will work but I'm interested in what will perform the fastest. Thanks for any help.

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  • Fastest method for SQL Server inserts, updates, selects from C# ASP.Net 2.0+

    - by Ian
    Hi All, long time listener, first time caller. I use SPs and this isn't an SP vs code-behind "Build your SQL command" question. I'm looking for a high-throughput method for a backend app that handles many small transactions. I use SQLDataReader for most of the returns since forward only works in most cases for me. I've seen it done many ways, and used most of them myself. Methods that define and accept the stored procedure parameters as parameters themselves and build using cmd.Parameters.Add (with or without specifying the DB value type and/or length) Assembling your SP params and their values into an array or hashtable, then passing to a more abstract method that parses the collection and then runs cmd.Parameters.Add Classes that represent tables, initializing the class upon need, setting the public properties that represent the table fields, and calling methods like Save, Load, etc I'm sure there are others I've seen but can't think of at the moment as well. I'm open to all suggestions.

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  • mongodb php finding a subobject and removing it, $inc other subobject

    - by Mark
    I'm trying to delete the subobject 'apples' from my documents and update the 'fruitInventory' property, decrease by the amount of apples. I'm confused on how to proceed, should I use dot notation or do a full text search for apples? I don't know if this matters but you can assume apples will always be in field 1. // Document 1 { "1": { "apples": 3, "fruitInventory": 21, "oranges": 12, "kiwis": 3, "lemons": 3 }, "2": { "bananas": 4, "fruitInventory": 12, "oranges": 8, }, "_id": "1" } // Document 2 { "1": { "apples": 5, "fruitInventory": 10, "oranges": 2, "pears": 3 }, "2": { "bananas": 4, "fruitInventory": 6, "cherries": 2, }, "_id": "2" } Result should be like this: // Document 1 { "1": { "fruitInventory": 18, "oranges": 12, "kiwis": 3, "lemons": "3" }, "2": { "bananas": 4, "fruitInventory": 12, "oranges": 8, }, "_id": "1" } // Document 2 { "1": { "fruitInventory": 5, "oranges": "2", "pears": "3" }, "2": { "bananas": 4, "fruitInventory": 6, "cherries": 2, }, "_id": "2" } Thanks in advance for your help.

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  • MySQL Connection error in spring MVC

    - by nidhi
    i am working on spring MVC facing the following exception while connecting to my sql. Blocorg.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.) at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80) at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:572) at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:636) at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:665) at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:673) at org.springframework.jdbc.core.JdbcTemplate.queryForObject(JdbcTemplate.java:728) at org.springframework.jdbc.core.JdbcTemplate.queryForObject(JdbcTemplate.java:744) at org.springframework.jdbc.core.JdbcTemplate.queryForInt(JdbcTemplate.java:775) at com.trackmeetings.dao.InboxDAOImpl.getNotificationsCount(InboxDAOImpl.java:51) at com.trackmeetings.service.InboxService.getNotificationsCount(InboxService.java:56) at com.trackmeetings.controller.HomePageController.getLogInUserDetails(HomePageController.java:80) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:175) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:421) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:409) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:774) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560) at javax.servlet.http.HttpServlet.service(HttpServlet.java:710) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.trackmeetings.util.NoCacheFilter.doFilter(NoCacheFilter.java:56) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:680) Caused by: org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.) at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1225) at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880) at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111) at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77) ... 38 more Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failurekquote how can i resolve this. please help,

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  • How to move an element in a sorted list and keep the CouchDb write "atomic"

    - by karlthorwald
    I have elements of a list in couchdb documents. Let's say these are 3 elements in 3 documents: { "id" : "783587346", "type" : "aList", "content" : "joey", "sort" : 100.0 } { "id" : "358734ff6", "type" : "aList", "content" : "jill", "sort" : 110.0 } { "id" : "abf587346", "type" : "aList", "content" : "jack", "sort" : 120.0 } A view retrieves all "aList" documents and displays them sorted by "sort". Now I want to move the elements, when I want to move "jack" to the middle, I could do this atomic in one write and change it's sort key to 105.0. The view now returns the documents in the new sort order. After a lot of sorting I could end up with sort keys like 50.99999 and 50.99998 after some years and in extreme situations run out of digits? What can you recommend, is there a better way to do this? I'd rather keep the elements in seperate documents. Different users might edit different elements in parallel (which also can get tricky). Maybe there is a much better way?

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  • Search & Replace SQL

    - by Shonna
    I am messing around with one of my databases.. is there away for me to search for a string in ALL the tables.. and replace it with another everywhere it occurs? I am looking for SQL

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  • Multiple table relationships in Zend Help

    - by Zogi
    Hi Guys I have been doing some DB mapping to link two tables to no avail. Everytime I run the code I get the following error: Message: File "Role.php" does not exist or class "Role" was not found in the file Stack trace: #0 C:\wamp\www\zend\library\Zend\Db\Table\Row\Abstract.php(867): Zend_Db_Table_Row_Abstract->_getTableFromString('Role') #1 C:\wamp\www\uw\application\models\admin\User.php(56): Zend_Db_Table_Row_Abstract->findDependentRowset('Role') #2 C:\wamp\www\uw\application\controllers\AdminController.php(110): Application_Model_Admin_User->getUsers() #3 C:\wamp\www\zend\library\Zend\Controller\Action.php(513): AdminController->usersAction() #4 C:\wamp\www\zend\library\Zend\Controller\Dispatcher\Standard.php(289): Zend_Controller_Action->dispatch('usersAction') #5 C:\wamp\www\zend\library\Zend\Controller\Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http)) #6 C:\wamp\www\zend\library\Zend\Application\Bootstrap\Bootstrap.php(97): Zend_Controller_Front->dispatch() #7 C:\wamp\www\zend\library\Zend\Application.php(366): Zend_Application_Bootstrap_Bootstrap->run() #8 C:\wamp\www\uwi\public\index.php(26): Zend_Application->run() #9 {main} Code & DB below: application/models/admin/User.php class Application_Model_Admin_User extends Zend_Db_Table_Abstract { protected $_name = 'user'; protected $_dependentTables = array('Role'); public function getUsers() { $rows = $this->fetchAll($this->select()->where('active = ?', 1)); $rows1 = $rows->current(); $rows2 = $rows1->findDependentRowset('Role'); return $rows2; } } application/models/admin/Role.php class Application_Model_Admin_Role extends Zend_Db_Table_Abstract { protected $_name = 'role'; protected $_referenceMap = array ( 'Role' => array( 'columns' => array('id'), 'refTableClass' => 'User', 'refColumns' => array('role_id') ); } DB tables CREATE TABLE role ( id integer auto_increment NOT NULL, name varchar(120), PRIMARY KEY(id) ); CREATE TABLE user ( id integer auto_increment NOT NULL, username varchar(120), PRIMARY KEY(id), FOREIGN KEY(role_id) REFERENCES role(id) );

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  • Struggling to create correct relationships in MS Access

    - by Yandawl
    http://img714.imageshack.us/img714/7820/croppercapture1.png Basically: an award(course) has many units, which can be either optional or core(mandatory), depending on the award. So for example: the unit 'Advanced Software Engineering' maybe a core unit for the award 'Software Engineering BSc' but only an optional unit for the course 'Web Technology BSc'. I've used flags for that purpose. A student is enrolled on an award so I need to get a complete list of core and optional units (bearing in mind that a student chooses 1 out of many possible optional units). Also, these units have events, e.g, a lecture, workshop or seminar, etc. and those events have sessions or instances of events where students enrolled on that particular unit are required to attend, and those attendances are stored in a separate table to form a register. So I need a hierarchy of expanding the tables something like this I guess: Awards - Students - Units - Sessions - Attendances Any help with this would be appreciated... It's blowing my mind and I'm really close to going insane! My tutor didn't spot I'd got it wrong when I showed my original data model to him and it's due in next week! Thank you :D

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  • Implementing Model-level caching

    - by Byron
    I was posting some comments in a related question about MVC caching and some questions about actual implementation came up. How does one implement a Model-level cache that works transparently without the developer needing to manually cache, yet still remains efficient? I would keep my caching responsibilities firmly within the model. It is none of the controller's or view's business where the model is getting data. All they care about is that when data is requested, data is provided - this is how the MVC paradigm is supposed to work. (Source: Post by Jarrod) The reason I am skeptical is because caching should usually not be done unless there is a real need, and shouldn't be done for things like search results. So somehow the Model itself has to know whether or not the SELECT statement being issued to it worthy of being cached. Wouldn't the Model have to be astronomically smart, and/or store statistics of what is being most often queried over a long period of time in order to accurately make a decision? And wouldn't the overhead of all this make the caching useless anyway? Also, how would you uniquely identify a query from another query (or more accurately, a resultset from another resultset)? What about if you're using prepared statements, with only the parameters changing according to user input? Another poster said this: I would suggest using the md5 hash of your query combined with a serialized version of your input arguments. This would require twice the number of serialization options. I was under the impression that serialization was quite expensive, and for large inputs this might be even worse than just re-querying. And is the minuscule chance of collision worth worrying about? Conceptually, caching in the Model seems like a good idea to me, but it seems in practicality the developer should have direct control over caching and write it into the controller. Thoughts/ideas? Edit: I'm using PHP and MySQL if that helps to narrow your focus.

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