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  • Advice on Linq to SQL mapping object design

    - by fearofawhackplanet
    I hope the title and following text are clear, I'm not very familiar with the correct terms so please correct me if I get anything wrong. I'm using Linq ORM for the first time and am wondering how to address the following. Say I have two DB tables: User ---- Id Name Phone ----- Id UserId Model The Linq code generator produces a bunch of entity classes. I then write my own classes and interfaces which wrap these Linq classes: class DatabaseUser : IUser { public DatabaseUser(User user) { _user = user; } public Guid Id { get { return _user.Id; } } ... etc } so far so good. Now it's easy enough to find a users phones from Phones.Where(p => p.User = user) but surely comsumers of the API shouldn't need to be writing their own Linq queries to get at data, so I should wrap this query in a function or property somewhere. So the question is, in this example, would you add a Phones property to IUser or not? In other words, should my interface specifically be modelling my database objects (in which case Phones doesn't belong in IUser), or are they actually simply providing a set of functions and properties which are conceptually associated with a User (in which case it does)? There seems drawbacks to both views, but I'm wondering if there is a standard approach to the problem. Or just any general words of wisdom you could share. My first thought was to use extension methods but in fact that doesn't work in this case.

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  • Need to use query column value in nested subquery

    - by Dustin
    It seems I cannot use a column from the parent query in a sub query. How can I refactor this query to get what I need? dbo.func_getRelatedAcnts returns a table of related accounts (all children from a given account). Events and Profiles are related to accounts. SELECT COUNT(r.reg_id) FROM registrations r JOIN profiles p ON (r.reg_frn_pro_id = p.pro_id) JOIN events e ON (r.reg_frn_evt_id = e.evt_id) WHERE evt_frn_acnt_id NOT IN (SELECT * FROM dbo.func_getRelatedAcnts(p.pro_frn_acnt_id))

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  • Best way to run multiple queries per second on database, performance wise?

    - by Michael Joell
    I am currently using Java to insert and update data multiple times per second. Never having used databases with Java, I am not sure what is required, and how to get the best performance. I currently have a method for each type of query I need to do (for example, update a row in a database). I also have a method to create the database connection. Below is my simplified code. public static void addOneForUserInChannel(String channel, String username) throws SQLException { Connection dbConnection = null; PreparedStatement ps = null; String updateSQL = "UPDATE " + channel + "_count SET messages = messages + 1 WHERE username = ?"; try { dbConnection = getDBConnection(); ps = dbConnection.prepareStatement(updateSQL); ps.setString(1, username); ps.executeUpdate(); } catch(SQLException e) { System.out.println(e.getMessage()); } finally { if(ps != null) { ps.close(); } if(dbConnection != null) { dbConnection.close(); } } } And my DB connection private static Connection getDBConnection() { Connection dbConnection = null; try { Class.forName(DB_DRIVER); } catch (ClassNotFoundException e) { System.out.println(e.getMessage()); } try { dbConnection = DriverManager.getConnection(DB_CONNECTION, DB_USER,DB_PASSWORD); return dbConnection; } catch (SQLException e) { System.out.println(e.getMessage()); } return dbConnection; } This seems to be working fine for now, with about 1-2 queries per second, but I am worried that once I expand and it is running many more, I might have some issues. My questions: Is there a way to have a persistent database connection throughout the entire run time of the process? If so, should I do this? Are there any other optimizations that I should do to help with performance? Thanks

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  • How do I go about link web content in a database with a nested set model?

    - by wb
    My nested set table is as follows. create table depts ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) , abbrv nvarchar(20) ); Test departments. insert into depts (lft, rgt, name, abbrv) values (1, 14, 'root', 'r'); insert into depts (lft, rgt, name, abbrv) values (2, 3, 'department 1', 'd1'); insert into depts (lft, rgt, name, abbrv) values (4, 5, 'department 2', 'd2'); insert into depts (lft, rgt, name, abbrv) values (6, 13, 'department 3', 'd3'); insert into depts (lft, rgt, name, abbrv) values (7, 8, 'sub department 3.1', 'd3.1'); insert into depts (lft, rgt, name, abbrv) values (9, 12, 'sub department 3.2', 'd3.2'); insert into depts (lft, rgt, name, abbrv) values (10, 11, 'sub sub department 3.2.1', 'd3.2.1'); My web content table is as follows. create table content ( id int identity(0, 1) , dept_id int , page_name nvarchar(60) , content ntext ); Test content. insert into content (dept_id, page_name, content) values (3, 'index', '<h2>welcome to department 3!</h2>'); insert into content (dept_id, page_name, content) values (4, 'index', '<h2>welcome to department 3.1!</h2>'); insert into content (dept_id, page_name, content) values (6, 'index', '<h2>welcome to department 3.2.1!</h2>'); insert into content (dept_id, page_name, content) values (2, 'what-doing', '<h2>what is department 2 doing?/h2>'); I'm trying to query the correct page content (from the content table) based on the url given. I can easily accomplish this task with a root department. However, querying a department with multiple depths is proving to be a little harder. For example: http://localhost/departments.asp?d3/ (Should return <h2>welcome to department 3!</h2>) http://localhost/departments.asp?d2/what-doing (Should return <h2>what is department 2 doing?</h2>) I'm not sure if this can be create in one query or if there will need to be a recursive function of some sort. Also, if there is nothing after the last / then assume we want the index page. How can this be accomplished? Thank you.

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  • What are the Limitations for Connecting to an Access Query in Excel

    - by thornomad
    I have an Access 2007 database that has a number of tables, some are fairly large (100,000+ records); I have created a union query to pull some of the same types of data from multiple tables into one large query for pivot table manipulation and reporting. For example: SELECT Language FROM Table1 UNION ALL SELECT Language FROM Table2 UNION ALL SELECT Language FROM Table3; This works. I found, quickly, however, that a union query will not show up when connecting to the datasource from Excel 2007. So, I created a second query to reference the union query. Like so: SELECT * FROM [The Above Union Query]; This query works and it, initially, was accessible from Excel. Time passed, I've added more data. Suddenly, when I connect to my Access database from Excel my query referencing the union has disappeared. MS Access shows no signs of an issue (data displays in Access) and my other non-union queries are showing up in Excel 2007 ... but not the one that references the union. What could be going on? Why did it disappear? I noticed if I switch some of the referenced tables in the union query to a smaller table (with less rows) all of sudden the query appears in Excel again. At least, I think that's what the difference is. I really can't put my finger on why some of the union queries won't show up and some will. Am stumped and need some guidance. Thanks.

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  • Accessing an Access DB from Outlook via VBA

    - by camastanta
    Hi The situation: In Outlook I get a message from a server. The content of the message needs to be put into an Access db. But, there may not exist another message with the same date. So, I need to look into a db if there is already a message with the same date and time. If there exists one, then it needs to be replaced and otherwise the message needs to be added to the database. The database contains a list of current positions from the vehicles on the road. The problem: I have problems to compare a date time with a date time in an Access DB via VBA. The query I use returns no records but there is a record in the database. This is the query I use: adoRS.Open "SELECT * FROM currentpositions WHERE ((currentpositions. [dateLT])=" & "#" & date_from_message & "#" & ")", adoConn, adOpenStatic, adLockOptimistic Second I need to now what the result is of that query. How can I determine the number of records that my query gives me? Thanks camastanta

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  • Returning a recordcount from a subquery in a result set.

    - by KeRiCr
    I am attempting to return a rowcount from a subquery as part of a result set. Here is a sample that I've tried that didn't work: SELECT recordID , GroupIdentifier , count() AS total , (SELECT COUNT() FROM table WHERE intActingAsBoolean = 1) AS Approved FROM table WHERE date_format(Datevalue, '%Y%m%d') BETWEEN 'startDate' AND 'endDate' GROUP BY groupIdentifier What I'm attempting to return for 'Approved' is the number of records for the grouped value where intActingAsBoolean = 1. I have also tried modifying the where clause by giving the main query a table alias and applying an AND clause to match the groupidentifier in the subquery to the main query. None of these are returning the correct results. The query as written returns all records in the table where intActingAsBoolean = 1. This query is being run against a MySQL database.

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  • Storing object into cache using Linq classes and velocity

    - by Arun
    I careated couple of linq classes & marked the datacontext as unidirectional. Out of four classes; one is main class while other three are having the one to many relationship with first one; When I load the object of main class & put into the memory OR serialize it into an XML file; I never get the child class data while it is maked as DataContractAttribute. How can I force object to put the child class data into XML file or into cache ?

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  • MySQL: Question about SELECT WHERE AND/OR

    - by Andrew
    I'm trying to write a query that returns the same result from three different events, but I think I am doing it wrong. I can run my query against one event ID and it works. How can I select all three? Here's what I have so far: SELECT * FROM `Registrations` WHERE `Role` = "Attendee" AND `RegistrationStatus_ID` = "1" AND `DigSignature` IS NULL AND `Event_ID` = "147" OR `Event_ID` = "155" OR `Event_ID` = "160"

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  • How to handle Foreign key for optional field in .NET

    - by brz dot net
    What is the best way to handle following situation? A dropdown(for master table) is optional in a particular form. But, In database table the field is constrained with foreign key. If user don't select from dropdown then It creates problem because of foreign key. One solution is to create default option in master table and use it in case of blank selection. but in dropdown, we need to handle this to show on top. Is it perfect solution? Is there any other optimized solution for this? Thanks

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  • Migrating Data to MSSQL 2008

    - by Fred Clown
    I am trying to migrate data from an Informix database to MSSQL 2008. I've got quite a lot of data to move. I've been try multiple methods to get the data over, and so far SQLBulkCopy in multiple chunks seems to be the fastest that I can find. Does anyone know of a faster means of getting the data over? I'm trying to cut down on the transfer time so that on my cut-over date I don't run out of time to do the full cut-over. Thanks.

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  • How can i learn Table Name in database an column name?

    - by Phsika
    How can i learn table Name in database an how can i learn any Table's Column name? SELECT Col.COLUMN_NAME, Col.DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS AS Col LEFT OUTER JOIN INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE AS Usg ON Col.TABLE_NAME = Usg.TABLE_NAME AND Col.COLUMN_NAME = Usg.COLUMN_NAME LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS Con ON Usg.CONSTRAINT_NAME = Con.CONSTRAINT_NAME WHERE Col.TABLE_NAME = 'Addresses_Temp' AND Con.Constraint_TYPE = 'PRIMARY KEY' But it returns to me empty data:(

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  • How can I kill MySQL queries every 60 seconds in Windows?

    - by Ethan Allen
    I want to check my MySQL server every minute and kill queries that have run longer than 150 seconds. The main reason I want to do this is because I don't want queries from certain people to lock up the DB for everyone else. I know this is not the ultimate solution to the problem, but at least it's a fallback in case something goes wrong with a query. I don't have a slave DB (this is just an at-home project). I'd like to schedule a script to run that does this for me. I'm unfamiliar with Perl or Ruby and I need it done on my Windows 2008 Server box. I've looked into creating a simple cmd line script, but that doesn't seem to be possible. I know currently I can do something like this but I have to do it manually: mysqladmin processlist mysqladmin kill Anyone have any ideas or examples on how I could do this?

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  • MySQL: Limit output according to associated ID

    - by Jess
    So here's my situation. I have a books table and authors table. An author can have many books... In my authors page view, the user (logged in) can click an author in a tabled row and be directed to a page displaying the author's books (collected like this URI format: viewauthorbooks.php?author_id=23), very straight forward... However, in my query, I need to display the books for the author only, and not all books stored in the books table (as i currently have!) As I am a complete novice, I used the most simple query of: SELECT * FROM tasks_tb This returns the books for me, but returns every single value (book) in the database, and not ones associated with the selected author. And when I click a different author the same books are displayed for them...I think everyone gets what I'm trying to achieve, I just don't know how to perform the query. I'm guessing that I need to start using more advanced query clauses like INNER JOIN etc. Anyone care to help me out :)

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  • get records from sqlite group by month

    - by peacmaker
    hi i hve an sqlite db which contain transactions each transaction has an price and has an transDate i want to retrieve the sum of the transaction group by month so the retrieved records should be like the following Price month 230 2 500 3 400 4 pleas any help

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  • Does AsEnumerable() cache all result (LINQ)

    - by Akshay
    When we call a query operator on a sequence, a sequence-specific operator gets called. I mean if i call Where<>() operator on IEnumerable<>, the operator that will be called will be defined in Enumerable class and if it's called on IQueryable<>, the one defined in Queryable class will be called. Consider the operator Reverse, defined in the Enumerable class. If i want to call it on Iqueryable<> then I must use the AsEnumerable<>() operator to first convert it into IEnumerable<>. db.Countries.OrderBy(cntry=>cntry.CountryName).AsEnumerable().Reverse() But the Reverse operator got to have all records at the same time so that it can reverse them. In the above code do all the records get loaded in memory first and then the Reverse() operator is reversing it ?

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  • Highlight row in report?

    - by sanjeev40084
    I have a SSRS report which displays hundred of rows. I was wondering if there is anyway i can highlight the rows so that i can easily know on which row i am while accessing the report. Any thoughts?

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  • Alternative to subqueries

    - by Juanma
    I'm using Mysql 5.1, and have this query, is there a way to not use the subqueries and accomplish the same result? SELECT oref.affiliate_id, ROUND(sum( oph.amount ) * 0.10 ,2) AS tsum FROM operators_referer AS oref LEFT JOIN operators_payments_history AS oph ON oref.operator_id = oph.operator_id WHERE oref.affiliate_id = 28221 AND ( oph.date_paid > ( SELECT MAX(aph.date_paid) FROM affiliates_payments_history AS aph WHERE aph.operator_id = oref.affiliate_id ) OR ( SELECT MAX(aph.date_paid) FROM affiliates_payments_history AS aph WHERE aph.operator_id = oref.affiliate_id ) is NULL )

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  • Select rows in random order and then reverse it

    - by Faruz
    I need to select rows in random order and return a query which holds the rows in both regular order and in reverse order. This is done to simulate a fantasy draft for a basketball game I'm working on. For example, I need a result set as followed: team1 1 team2 2 team6 3 team9 4 team9 5 team6 6 team2 7 team1 8 As you can see, the first four teams are random then then following four are in reverse order. Hope I managed to explain the problem, if not - please comment and I'll explain further.

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