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• Entity Framework 4 and 0:1, 0:1 relationships

  - by Eric J.

  I'm using the Model First approach with EF 4 and hit a snag with two tables, Participant (singular because pre-existing from another app) and ActiveParticipants. A Participant may or may not be associated with exactly one ActiveParticipant and vice versa. When I create an association, everything seems to go well on the surface, but then I get a runtime error complaining that Participant does not contain the column ActiveParticipant_Id. It does contain a column ActiveParticipantId (no underscore). When I view the diagram as XML, there's a line like this: <Property Name="ActiveParticipant_Id" Type="uniqueidentifier" Nullable="true" /> Why is it adding an underscore? Is there anything special I need to do for 0:1, 0:1 relationships?

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• MySQL is there a Single Select to Query Various Unrelated Values from a database?

  - by zzapper

  I saw somewhere what seemed to be nested selects, one "master" select on the "outside" and a series of selects inside- is this possible? I'm not talking about joins as there is particular relation between the selects. I seem not to be explaining myself very well. I want to do a single query which will pull out a series of stats from various tables latest order, latest customer, largest order. Obviously I can do that with a series of selects. The example I saw was something like select ( select ... from tbl_1 where .., select ... from tbl_2 where .., select ... from tbl_3 where .., ... )

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• SQL Server PIVOT on key-value table

  - by Zenox

  I have a table that has attributes based on a key-value. Example: CREATE TABLE ObjectAttributes ( int objectId, key nvarchar(64), value nvarchar(512) ) When I select from this I get: objectId key value ---------------------------- 1 Key 1 Value 1 1 Key 2 Value 2 I was wondering if I could use the PIVOT syntax to turn this into: objectId Key 1 Key 2 --------------------------- 1 Value 1 Value 2 I know all of my tables will have the same keys. (Unfortunately I cannot easily change the table structure. This is what is leading me to attempt using PIVOTS). The big issue here though is that pivots require an aggression function to be used. Is there a way to avert this? Am I completely wrong attempting this? Or is there a better solution?

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• mysql count(*) left join group by - the number of files in a folder

  - by Flavius

  Hi I have the following tables CREATE TABLE `files` ( `fileid` int(11) NOT NULL AUTO_INCREMENT, `filename` varchar(255) NOT NULL, `filesize` int(11) NOT NULL, `folder` int(11) NOT NULL, PRIMARY KEY (`fileid`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; CREATE TABLE `folders` ( `directoryid` int(11) NOT NULL AUTO_INCREMENT, `directoryname` varchar(255) NOT NULL, PRIMARY KEY (`directoryid`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; How to get a list of all folders and the number of files they hold, including folders who have no (zero) files? Recursion must not be taken into account. Found it select folders.directoryid, folders.directoryname, count(files.fileid) as no_files from folders left join files on files.folder = folders.directoryid group by folders.directoryid, folders.directoryname I hope it will help someone.

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• SQL Outer joins

  - by dsquaredtech

  Three tables courses,registration,students columns in students firstname,lastname,studentid,major,admitdate,graddate,gender,dob columns in registration courseid,studentid columns in courses coursenumber,coursename,credits select statement I need to modify select lastname as 'Last Name',sum(credits) as 'Credits Registered For' from students as s inner join registration as r on s.studentid = r.studentid inner join courses as c on c.coursenumber = c.courseid group by last name; the question on the lab is... Modify the previous query to show all students, even if they have not registered for a class. You should have 14 rows. Students who are not registered will show NULL in output. I know this requires outer join of some sort but I'm not fully grasping these joins i've read multiple posts on here and other sites but can't seem figure it out.

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• Running sql scripts against an attached database?

  - by Will

  I've got an MDF attached to an instance of Sql Server 2008 Express, and I need to run some sql scripts against it to generate tables, indexes, etc. But I can't figure out how to get this to work. If I load the scripts in Visual Studio, it only allows me to connect to the server and run it against a database. I can't choose a different provider (Microsoft Sql Server Database File), so I can't select my MDF. This leaves me the only option of running the script as individual queries, but that won't work as it appears it doesn't support TSQL CREATE statements. How can I run my sql script against an attached database?

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• Fastest method for SQL Server inserts, updates, selects

  - by Ian

  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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• Help me construct this Linq statement

  - by Geoffrey

  There should be a simple Linq query for what I'm trying to accomplish, but I'm producing some ugly code. I have two tables, one of issues and another of issue status. There is a one-to-many relationship between issue and issue status. When an issue is created an IssueStatus is also created with the status field set to "Open" when it is closed, another IssueStatus is created with the status field set to "Closed" ... but issues can be re-opened. It seems like I should be able to write something like this: public static List<Issue> FindOpenIssues(this IList<Issue> issues) { return ( from issue in issues from issueStatus in issue.issueStatus.OrderBy(x=>x.CreatedOn).Single() where issueStatus.Status == "Open" select issue ).ToList(); } This obviously fails, but there must be a clean way to do this? Thanks!

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• Oracle Sql: how to substract rows from one table from another only once

  - by slyder07

  I'm working for a university project, and I have the following question: I have 2 tables in a Oracle DB... I need to select those rows from table1, which are not included in table2... But the main problem is that I need to exclude that rows from table2 wich was selected once... For example: Table1 Table2 ResultTable id | Number | Letter id | Number | Letter id | Number | Letter _____________________ _____________________ _____________________ 1 4 S 1 6 G 2 2 P 2 2 P 2 8 B 3 5 B 3 5 B 3 4 S 4 4 S 4 4 S 4 1 A 6 2 P 5 1 A 5 1 H 6 2 P 6 2 X So, how you see it, if one row from Table1 has a "twin" in Table2, they both are excluded. Hope I was explicit enough. Sorry for my bad English. Thanks.

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• SQL Convert Nvarchar(255) to DateTime problem

  - by steven

  Hi, I'm using SQL server 2008. I have 2 Tables: Table 1 and Table 2. Table 1 has 1 column called: OldDate which is nvarchar(255), null Table 2 has 1 column called: NewDate which is datetime, not null Example data in Table 1: 26/07/03 NULL NULL 23/07/2003 7/26/2003 NULL 28/07/03 When i try CAST(OldDate as datetime) I get this error: Arithmetic overflow error converting expression to data type datetime. I need to insert OldDate into NewDate with no errors. I can't skip some rows. Anyhelp would be appreciated.

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• What do C# Table Adapters actually return?

  - by Raven Dreamer

  I'm working on an application that manipulates SQL tables in a windows form application. Up until now, I've only been using the pre-generated Fill queries, and self-made update and delete queries (which return nothing). I am interested in storing the value of a single value from a single column (an 'nchar(15)' name), and though I have easily written the SQL code to return that value to the application, I have no idea what it will be returned as. SELECT [Contact First Name] FROM ContactSkillSet WHERE [Contact ID] = @CurrentID Can the result be stored directly as a string? Do I need to cast it? Invoke a toString method?

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• MySQL, select from different table... IF

  - by gubbfett

  I'm having a small trouble since it was a long time ago i studies databases and querys. For example i'll have two tables for cd:s, one with data and one with alternative translations. In the CD-table i have the original language, and it looks something like this Table for CDs (cds): id | name | language ----------------------- 1 | aaa | en 2 | bbb | en 3 | ccc | fi Table for languages (languages): cd_id | language | name ----------------------- 1 | fi | AAA 1 | de | AAACHTUNG 3 | en | CCC Now, i want to get all these cd:s in for example german, if there's no translation made i want it to be in the original language... How can i do this?

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• How to organize database access code in Android project?

  - by Mladen Jablanovic

  I have created a ContentProvider for my main Sqlite table, pretty much following NotePad example from SDK (although I am not sure whether I will ever be exposing my data to other apps). However, I need to create lots of other, non-trivial queries on that and other tables and views. A good example would be queries to extract some statistics from the base data, averages, totals etc. So what's the best place for this code in an Android project? How it should be related and connected to the Uri-based data access exposed by a Provider? Any good examples out there?

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• how to use constants in SQL CREATE TABLE?

  - by kchiu

  Hi, I have 3 SQL tables, defined as follows: CREATE TABLE organs( abbreviation VARCHAR(16), -- ... other stuff ); CREATE TABLE blocks( abbreviation VARCHAR(16), -- ... other stuff ); CREATE TABLE slides( title VARCHAR(16), -- ... other stuff ); The 3 fields above all use VARCHAR(16) because they're related and have the same length restriction. Is there a (preferably portable) way to put '16' into a constant / variable and reference that instead in CREATE TABLE? eg. something like this would be nice: CREATE TABLE slides( title VARCHAR(MAX_TITLE_LENGTH), -- ... other stuff ); I'm using PostgreSQL 8.4. thanks a lot, and Happy New Year! cheers.

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• [sqlalchemy] subquery in select statement

  - by webjunkie

  Hi guys, I have two tables (albums,pictures) in a one to many relationship and I want to display each albums details with one picture so I have the following query select albums.name,(select pictures.path from pictures where pictures.albumid=albums.id limit 1) as picture from albums where ... Now I'm struggling creating this on Pylons with sqlalchemy I tried to do the following picture = Session.query(model.Picture) sub_q = picture.filter_by(albumid = model.Album.id).limit(1).subquery() album_q = Session.query(model.Album, sub_q) result = album_q.all() but it creates the following statement displaying the incorrect picture beacuse the table albums is included in the subquery select albums.name,(select pictures.path from pictures,albums where pictures.albumid=albums.id) from albums where ... Am I doing it wrong?, is this even possible in sqlalchemy?.

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• copy an identity column into another table

  - by slake

  I have 2 tables that are related,both have identity columns for primary keys and i am using a vb form to insert data into them,My problem is that i cannot get the child table to get the primary key of the parent table and use this as its foreign key in my database. the data is inserted fine though no foreign key constraint is made.I am wondering if a trigger will do it and if so how. All my inserting of data is done in vb. The user wont insert any keys. all these are identity columns that are auto generated. If a trigger is my way out please illustrate with an example. If there is another way i can do this in VB itself then please advise and an example will be greatly appreciated Thanks in advance

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• Handling missing data

  - by soppotare

  Say I have a simple helpdesk application which logs calls made by users. I would typically have such fields in a table relating to the call e.g. CallID, Description, CustomerID etc. I Would also have a table of customers including CustomerID, Username, Password, FullName etc. Now when a user is deleted from the customers table then the inner join between the calls table and the users table to find out historically which user logged a call would produce no results. How do people usually deal with this? Have seperate customer and useraccount tables Just disable the accounts so the data is still available Record the customers name in the calls table as a seperate field. or any other methods / suggestions?

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• How to make UPDATE queries in LINQ to SQL?

  - by Alex

  I like using LINQ to SQL. The only problem is that I don't like the default way of updating tables. Let's say I have the following table with the following columns: ID (primary key), value1, value2, value3, value4, value5 When I need to update something I call UPDATE ... WHERE ID=@id LINQ to SQL call UPDATE ... WHERE ID=@id and value1=@value1 and value2=@value2 and value3=@value3 and value4=@value4 and value5=@value5 I can override this behavior by adding UpdateCheck=UpdateCheck.Never to every column, but with every update of the DataContext class with the GUI, this will be erased. Is there any way to tell LINQ to use this way of updating data?

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• Extendable accessing of sqlite database on android platform

  - by mscriven

  Hi, I am fairly new to the android sdk and databases and have been searching for an answer to this quite some time. I am trying to build an app which has multiple tables within a database. e.g. one for weapons, armours etc. However, my DatabaseManager class which handles all of my table creating, DatabaseHelper inner class and populating of data is creating for an extremely large class requiring high maintenance. Every time I would like to add or remove a table column I need to change quite a few areas of code, - Every reference to the addition of a row in that table with data - The method that the above calls - The method returning all of the database rows - The code in the helper class creating the table - Any specific update methods My question is this: Surely there must be some better way of coding this system, maybe using a database isn't the best way to go, or am i just not used to such large classes having only learned java at university and my largest class consisting of a mere 400-600 lines of code. Thanks for any help!

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• How to insert into data base using multi threading programming [closed]

  - by user1196650

  I am having a method and that method needs to do the following thing: It has to insert records into a database. No insert is done for the same table again. All inserts are into different tables. I need a multi threading logic which inserts the details into db using different threads. I am using oracle db and driver configuration and remaining stuff are perfect. Please help me with an efficient answer. Can anyone could provide me with a skeleton logic of the program.

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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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• Entity Framework 4 & WCF Data Service: N:M mapping

  - by JJO

  I have three tables in my database: An A table, a B table, and a many-to-many ABMapping table. For simplicity, A and B are keyed with identity columns; ABMapping has just two columns: AId and BId. I built an Entity Framework 4 model from this, and it did correctly identify the N:M mapping between A and B. I then built a WCF Data Service based on this EF model. I'm trying to consume this WCF Data Service. Unfortunately, I can't figure out how to get a mapping between As and Bs to map back to the database. I've tried something like this: A a = new A(); B b = new B(); a.Bs.Add(b); connection.SaveChanges(); But this doesn't seem to have worked. Any clues? What am I missing?

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• 2 table SQL Query weird results

  - by javArc

  Ok this is driving me nuts, I need to write an SQL query that will grab product information from 2 tables. The first table 'products' contains the productId, productname, quantityperunit and unitprice. Now I can search by productname and categoryname individually, but when I try to combine the 2 I get crazy results, Here's the query: "SELECT DISTINCT productId, productname, quantityperunit, unitprice FROM products pr, categories ca WHERE pr.categoryID = ca.categoryID AND ProductName LIKE '%" + searchTerm + "%' OR CategoryName LIKE '%" + searchTerm + "%' excuse the java style in there, here it is formatted better: SELECT DISTINCT productId, productname, quantityperunit, unitprice FROM products pr, categories ca WHERE pr.categoryID = ca.categoryID AND ProductName LIKE 'Tofu' OR CategoryName LIKE 'Tofu' any help would be appreciated.

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• Normalize database or not? Read only MyISAM table, performance is the main priority (MySQL)

  - by hello

  I'm importing data to a future database that will have one, static MyISAM table (will only be read from). I chose MyISAM because as far as I understand it's faster for my requirements (I'm not very experienced with MySQL / SQL at all). That table will have various columns such as ID, Name, Gender, Phone, Status... and Country, City, Street columns. Now the question is, should I create tables (e.g Country: Country_ID, Country_Name) for the last 3 columns and refer to them in the main table by ID (normalize...[?]), or just store them as VARCHAR in the main table (having duplicates, obviously)? My primary concern is speed - since the table won't be written into, data integrity is not a priority. The only actions will be selecting a specific row or searching for rows that much a certain criteria. Would searching by the Country, City and/or Street columns (and possibly other columns in the same search) be faster if I simply use VARCHAR?

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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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