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  • Problem with LINQ in C#

    - by David Bonnici
    I am encountering a problem when using LINQ in C#, I am constantly getting "Specified cast is not valid". This is what I am trying to do. I create a class in which I declare all the columns of the table. [Table(Name="tbl_Aff")] public class Affiliate { [Column] public string name; [Column] public string firstname; [Column] public string surname; [Column] public string title; } I then declare a strongly typed DataContext in which I declare all Table collections as members of the context. public partial class Database : DataContext { public Table affiliate; public Database() : base(Settings.getConnectionString()) { } //This method gets the connection string by reading from an XML file. } public partial class Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Database database = new Database(); try { var q = from a in database.affiliate select a; foreach (var aff in q) // Here I get the error "Specified cast is not valid" { lblMessage.InnerHtml += aff.name + ""; } } catch (Exception ex) { System.Console.WriteLine(ex.Message); } } }

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  • Repository vs Data Access

    - by vdh_ant
    Hi guys In the context of the n-tier application, is there a difference between what you would consider your data access classes to be and your repositories? I tend to think yes but I just wanted to see what other thought. My thinking is that the job of the repository is just to contain and execute the raw query itself, where as the data access class would create the context, execute the repository (passing in the context), handle mapping the data model to the domain model and return the result back up... What do you guys think? Also do you see any of this changing in a Linq to XML scenario (assuming that you change the context for the relevant XDocument)? Cheers Anthony

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  • Display another field in the referenced table for multiple columns with performance issues in mind

    - by israkir
    I have a table of edge like this: ------------------------------- | id | arg1 | relation | arg2 | ------------------------------- | 1 | 1 | 3 | 4 | ------------------------------- | 2 | 2 | 6 | 5 | ------------------------------- where arg1, relation and arg2 reference to the ids of objects in another object table: -------------------- | id | object_name | -------------------- | 1 | book | -------------------- | 2 | pen | -------------------- | 3 | on | -------------------- | 4 | table | -------------------- | 5 | bag | -------------------- | 6 | in | -------------------- What I want to do is that, considering performance issues (a very big table more than 50 million of entries) display the object_name for each edge entry rather than id such as: --------------------------- | arg1 | relation | arg2 | --------------------------- | book | on | table | --------------------------- | pen | in | bag | --------------------------- What is the best select query to do this? Also, I am open to suggestions for optimizing the query - adding more index on the tables etc... EDIT: Based on the comments below: 1) @Craig Ringer: PostgreSQL version: 8.4.13 and only index is id for both tables. 2) @andrefsp: edge is almost x2 times bigger than object.

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  • ProviderException: InvalidCastException

    - by JS
    Few of our clients are regularly getting invalid cast exception, with variations i.e. InvalidCastException / ProviderException, but both generating from method call: System.Web.Security.SqlRoleProvider.GetRolesForUser(String username) The other variation is: Exception type: InvalidCastException Exception message: Unable to cast object of type System.Int32 to type System.String. I had a look at application event log which shows: Stack trace: at System.Web.Security.SqlRoleProvider.GetRolesForUser(String username) at System.Web.Security.RolePrincipal.IsInRole(String role) at System.Web.Configuration.AuthorizationRule.IsTheUserInAnyRole(StringCollection roles, IPrincipal principal) at System.Web.Configuration.AuthorizationRule.IsUserAllowed(IPrincipal user, String verb) at System.Web.Configuration.AuthorizationRuleCollection.IsUserAllowed(IPrincipal user, String verb) at System.Web.Security.UrlAuthorizationModule.OnEnter(Object source, EventArgs eventArgs) at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)* Has anyone come across this issue, and if so what is the fix? Thanks JS

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  • How to skip all the column names in MySQL when the table has auto increment primary key?

    - by Jian Lin
    A table is: mysql> desc gifts; +---------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+-------------+------+-----+---------+----------------+ | giftID | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(80) | YES | | NULL | | | filename | varchar(80) | YES | | NULL | | | effectiveTime | datetime | YES | | NULL | | +---------------+-------------+------+-----+---------+----------------+ the following is ok: mysql> insert into gifts -> values (10, "heart", "heart_shape.jpg", now()); Query OK, 1 row affected (0.05 sec) but is there a way to not specify the "10"... and just let each one be 11, 12, 13... ? I can do it using mysql> insert into gifts (name, filename, effectiveTime) -> values ("coffee", "coffee123.jpg", now()); Query OK, 1 row affected (0.00 sec) but the column names need to be all specified. Is there a way that they don't have to be specified and the auto increment of primary key still works? thanks.

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  • How to avoid timestamp issue in a long query?

    - by pingi
    Hi, I have the following 2 tables: items: id int primary key bla text events: id_items int num int when timestamp without time zone ble text composite primary key: id_items, num and want to select to each item the most recent event (the newest 'when'). I wrote an request, but I don't know if it could be written more efficiently. Also on PostgreSQL there is a issue with comparing Timestamp objects: 2010-05-08T10:00:00.123 == 2010-05-08T10:00:00.321 so I select with 'MAX(num)' Any thoughts how to make it better? Thanks. SELECT i.*, ea.* FROM items AS i JOIN ( SELECT t.s AS t_s, t.c AS t_c, max(e.num) AS o FROM events AS e JOIN ( SELECT DISTINCT id_item AS s, MAX(when) AS c FROM events GROUP BY s ORDER BY c ) AS t ON t.s = e.id_item AND e.when = t.c GROUP BY t.s, t.c ) AS tt ON tt.t_s = i.id JOIN events AS ea ON ea.id_item = tt.t_s AND ea.cas = tt.t_c AND ea.num = tt.o;

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  • Complex SQL query, one to many relationship

    - by Ethan
    Hey SO, I have a query such that I need to get A specific dog All comments relating to that dog The user who posted each comment All links to images of the dog the user who posted each link I've tried a several things, and can't figure out quite how to work it. Here's what I have (condensed so you don't have to wade through it all): SELECT s.dog_id, s.name, c.comment, c.date_added AS comment_date_added, u.username AS comment_username, u.user_id AS comment_user_id, l.link AS link, l.date_added AS link_date_added, u2.username AS link_username, u2.user_id AS link_user_id FROM dogs AS d LEFT JOIN comments AS c ON c.dog_id = d.dog_id LEFT JOIN users AS u ON c.user_id = u.user_id LEFT JOIN links AS l ON l.dog_id = d.dog_id LEFT JOIN users AS u2 ON l.user_id = u2.user_id WHERE d.dog_id = '1' It's sorta close to working, but it'll only return me the first comment, and the first link all as one big array with all the info i requested. The are multiple comments and links per dog, so I need it to give me all the comments and all the links. Ideally it'd return an object with dog_id, name, comments(an array of the comments), links(an array of the links) and then comments would have a bunch of comments, date_added, username, and user_id and links would have a bunch of links with link, date_added, username and user_id. It's got to work even if there are no links or comments. I learned the basics of mySQL somewhat recently, but this is pretty far over my head. Any help would be wonderful. Thanks!

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  • How to manage multiple versions of the same record

    - by Darvis Lombardo
    I am doing short-term contract work for a company that is trying to implement a check-in/check-out type of workflow for their database records. Here's how it should work... 1) A user creates a new entity within the application. There are about 20 related tables that will be populated in addition to the main entity table. 2) Once the entity is created the user will mark it as the master. 3) Another user can make changes to the master only by "checking out" the entity. Multiple users can checkout the entity at the same time. 4) Once the user has made all the necessary changes to the entity, they put it in a "needs approval" status. 5) After an authorized user reviews the entity, they can promote it to master which will put the original record in a tombstoned status. The way they are currently accomplishing the "check out" is by duplicating the entity records in all the tables. The primary keys include EntityID + EntityDate, so they duplicate the entity records in all related tables with the same EntityID and an updated EntityDate and give it a status of "checked out". When the record is put into the next state (needs approval), the duplication occurs again. Eventually it will be promoted to master at which time the final record is marked as master and the original master is marked as dead. This design seems hideous to me, but I understand why they've done it. When someone looks up an entity from within the application, they need to see all current versions of that entity. This was a very straightforward way for making that happen. But the fact that they are representing the same entity multiple times within the same table(s) doesn't sit well with me, nor does the fact that they are duplicating EVERY piece of data rather than only storing deltas. I would be interested in hearing your reaction to the design, whether positive or negative. I would also be grateful for any resoures you can point me to that might be useful for seeing how someone else has implemented such a mechanism. Thanks! Darvis

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  • make multiple, composite query in oracle

    - by Meloun
    How can i make multiple, composite query in oracle? for example this several queries in one step? 1 CREATE TABLE test (id NUMBER PRIMARY KEY, name VARCHAR2(30)); 2 CREATE SEQUENCE test_sequence START WITH 1 INCREMENT BY 1; 3 CREATE OR REPLACE TRIGGER test_trigger BEFORE INSERT ON test REFERENCING NEW AS NEW FOR EACH ROW BEGIN SELECT test_sequence.nextval INTO :NEW.ID FROM dual; END; 4 INSERT INTO test (name) VALUES ('Jon'); 5 INSERT INTO test (name) VALUES ('Meloun');

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  • Databinding multiple tables linq query to gridview?

    - by Curtis White
    My question is how can I display a linq query in a gridview that has data from multiple tables AND allow the user to edit some of the fields or delete the data from a single table? I'd like to do this with either a linqdatasource or a linq query. I'm aware I can set the e.Result to the query on the selecting event. I've also been able to build a custom databound control for displaying the linq relations (parent.child). However, I'm not sure how I can make this work with delete? I'm thinking I may need to handle the delete event with custom code.

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  • (N)Hibernate: deleting orphaned ternary association rows when either associated row is deleted.

    - by anthony
    I have a ternary association table created using the following mapping: <map name="Associations" table="FooToBar"> <key column="Foo_id"/> <index-many-to-many class="Bar" column="Bar_id"/> <element column="AssociationValue" /> </map> I have 3 tables, Foo, Bar, and FooToBar. When I delete a row from the Foo table, the associated row (or rows) in FooToBar is automatically deleted. This is good. When I delete a row from the Bar table, the associated row (or rows) in FooToBar remain, with a stale reference to a Bar id that no longer exists. This is bad. How can I modify my hbm.xml to remove stale FooToBar rows when deleting from the Bar table?

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  • Nested mysql select statements

    - by Jimmy Kamau
    I have a query as below: $sult = mysql_query("select * from stories where `categ` = 'businessnews' and `stryid`='".mysql_query("SELECT * FROM comments WHERE `comto`='".mysql_query("select * from stories where `categ` ='businessnews'")." ORDER BY COUNT(comto) DESC")."' LIMIT 3") or die(mysql_error()); while($ow=mysql_fetch_array($sult)){ The code above should return the top 3 'stories' with the most comments {count(comto)}. The comments are stored in a different table from the stories. The code above does not return any values and doesn't show any errors. Could someone please help?

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  • MYSQL join - reference external field from nested select?

    - by PHP thinker
    Is it allowed to reference external field from nested select? E.g. SELECT FROM ext1 LEFT JOIN (SELECT * FROM int2 WHERE int2.id = ext1.some_id ) as x ON 1=1 in this case, this is referencing ext1.some_id in nested select. I am getting errors in this case that field ext1.some_id is unknow. Is it possible? Is there some other way?

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  • Question about Cost in Oracle Explain Plan

    - by Will
    When Oracle is estimating the 'Cost' for certain queries, does it actually look at the amount of data (rows) in a table? For example: If I'm doing a full table scan of employees for name='Bob', does it estimate the cost by counting the amount of existing rows, or is it always a set cost?

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  • Which Oracle table uses a sequence?

    - by Jaú
    Having a sequence, I need to find out which table.column gets its values. As far as I know, Oracle doesn't keep track of this relationship. So, looking up for the sequence in source code would be the only way. Is that right? Anyone knows of some way to find out this sequence-table relationship?

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  • LinQ: Add list to a list

    - by JohannesBoersma
    I have the following code: var columnNames = (from autoExport in dataContext.AutoExports where autoExport.AutoExportTemplate != null && ContainsColumn(autoExport.AutoExportTemplate, realName) select GetDbColumnNames(autoExport.AutoExportTemplate, realName)).ToList(); Where the function GetDbColumns() returns an List<string>. So columNames is of the type List<List<string>>. Is it possible to create a List<string>, so each element of the list of GetDbColumns is added to the result of the LinQ query?

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  • Is closing/disposing an SqlDataReader needed if you are already closing the sqlconnection?

    - by Brian
    I noticed This question, but my question is a bit more specific. Is there any advantage to using using (SqlConnection conn = new SqlConnection(conStr)) { using (SqlCommand command = new SqlCommand()) { // dostuff } } instead of using (SqlConnection conn = new SqlConnection(conStr)) { SqlCommand command = new SqlCommand(); // dostuff } Obviously it does matter run more than one command with the same connection, since closing an SqlDataReader is more efficient than closing and reopening a connection (calling conn.Close();conn.Open(); will also free up the connection). I see many people insist that failure to close the DataReader means leaving open connection resources around, but doesn't that only apply if you don't close the connection?

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  • Extending LINQ classes to my own partial classes in different namespaces?

    - by sah302
    I have a .dbml file which of course contains the auto-generated classes based on my tables. I would however, like to extend them to my own classes. Typically I design such that each of my tables get their own namespace in their own folder containing all of their associated dao and service classes. So if I am dealing with a page that only has to do with 'customers' for instance, I can only include the customerNS. But when using LINQ I seem to be unable to do this. I have tried removing a default namespace from the project, I have tried putting the .dbml file into it's own folder with a custom namespace and then adding a 'using' statement, but no nothing works. I also saw the Entity Namespace, Context Namespace, and Custom Tool Namespace properties associated with the .dbml file and tried setting all these to names x and trying 'using x' in my other class to allow me to extend partial classes, but it just doesn't work. Is this possible or do I have to keep all extended partial classes in the same namespace as the .dbml file?

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  • how to design a schema where the columns of a table are not fixed

    - by hIpPy
    I am trying to design a schema where the columns of a table are not fixed. Ex: I have an Employee table where the columns of the table are not fixed and vary (attributes of Employee are not fixed and vary). Nullable columns in the Employee table itself i.e. no normalization Instead of adding nullable columns, separate those columns out in their individual tables ex: if Address is a column to be added then create table Address[EmployeeId, AddressValue]. Create tables ExtensionColumnName [EmployeeId, ColumnName] and ExtensionColumnValue [EmployeeId, ColumnValue]. ExtensionColumnName would have ColumnName as "Address" and ExtensionColumnValue would have ColumnValue as address value. Employee table EmployeeId Name ExtensionColumnName table ColumnNameId EmployeeId ColumnName ExtensionColumnValue table EmployeeId ColumnNameId ColumnValue There is a drawback is the first two ways as the schema changes with every new attribute. Note that adding a new attribute is frequent. I am not sure if this is the good or bad design. If someone had a similar decision to make, please give an insight on things like foreign keys / data integrity, indexing, performance, reporting etc.

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  • Upgraded activerecord-sqlserver-adapter from 2.2.22 to 2.3.8 and now getting an ODBC error

    - by stuartc
    I have been using MSSQL 2005 with Rails for quite a while now, and decided to bump my gems up on one of my projects and ran into a problem. I moved from 2.2.22 to 2.3.8 (latest as of writing) and all of a sudden I got this: ODBC::Error: S1090 (0) [unixODBC][Driver Manager]Invalid string or buffer length I'm using a DSN connection with FreeTDS my database.yml looks like this: adapter: sqlserver mode: ODBC dsn: 'DRIVER=FreeTDS;TDSVER=7.0;SERVER=10.0.0.5;DATABASE=db;Port=1433;UID=user;PWD=pwd;' Now in the mean time I moved back to 2.2.22 and there are no deprecation warnings and everything seems fine but obviously for the sake of being up to date, any ideas what could have changed in the adaptor that could cause this?

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  • Precision of Interval for PL/SQL Function value

    - by Gary
    Generally, when you specify a function the scale/precision/size of the return datatype is undefined. For example, you say FUNCTION show_price RETURN NUMBER or FUNCTION show_name RETURN VARCHAR2. You are not allowed to have FUNCTION show_price RETURN NUMBER(10,2) or FUNCTION show_name RETURN VARCHAR2(20), and the function return value is unrestricted. This is documented functionality. Now, I get an precision error (ORA-01873) if I push 9999 hours (about 400 days) into the following. The limit is because the default days precision is 2 DECLARE v_int INTERVAL DAY (4) TO SECOND(0); FUNCTION hhmm_to_interval return INTERVAL DAY TO SECOND IS v_hhmm INTERVAL DAY (4) TO SECOND(0); BEGIN v_hhmm := to_dsinterval('PT9999H'); RETURN v_hhmm; -- END hhmm_to_interval; BEGIN v_int := hhmm_to_interval; end; / and it won't allow the precision to be specified directly as part of the datatype returned by the function. DECLARE v_int INTERVAL DAY (4) TO SECOND(0); FUNCTION hhmm_to_interval return INTERVAL DAY (4) TO SECOND IS v_hhmm INTERVAL DAY (4) TO SECOND(0); BEGIN v_hhmm := to_dsinterval('PT9999H'); RETURN v_hhmm; -- END hhmm_to_interval; BEGIN v_int := hhmm_to_interval; end; / I can use a SUBTYPE DECLARE subtype t_int is INTERVAL DAY (4) TO SECOND(0); v_int INTERVAL DAY (4) TO SECOND(0); FUNCTION hhmm_to_interval return t_int IS v_hhmm INTERVAL DAY (4) TO SECOND(0); BEGIN v_hhmm := to_dsinterval('PT9999H'); RETURN v_hhmm; -- END hhmm_to_interval; BEGIN v_int := hhmm_to_interval; end; / Any drawbacks to the subtype approach ? Any alternatives (eg some place to change a default precision) ? Working with 10gR2.

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