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  • Passing filtering functions to Where() in LINQ-to-SQL

    - by Daniel
    I'm trying to write a set of filtering functions that can be chained together to progressively filter a data set. What's tricky about this is that I want to be able to define the filters in a different context from that in which they'll be used. I've gotten as far as being able to pass a very basic function to the Where() clause in a LINQ statement: filters file: Func<item, bool> returnTrue = (i) => true; repository file: public IQueryable<item> getItems() { return DataContext.Items.Where(returnTrue); } This works. However, as soon as I try to use more complicated logic, the trouble begins: filters file: Func<item, bool> isAssignedToUser = (i) => i.assignedUserId == userId; repository file: public IQueryable<item> getItemsAssignedToUser(int userId) { return DataContext.Items.Where(isAssignedToUser); } This won't even build because userId isn't in the same scope as isAssignedToUser(). I've also tried declaring a function that takes the userId as a parameter: Func<item, int, bool> isAssignedToUser = (i, userId) => i.assignedUserId == userId; The problem with this is that it doesn't fit the function signature that Where() is expecting: Func<item, bool> There must be a way to do this, but I'm at a loss for how. I don't feel like I'm explaining this very well, but hopefully you get the gist. Thanks, Daniel

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  • SQL using sum to count results of multiple subqueries

    - by asdas
    I have a table with 2 columns: integer and var char. I am given only the integer values but need to do work on the var char (string) values. Given an integer, and a list of other integers (no overlap), I want to find the string for that single integer. Then I want to take that string and do the INSTR command with that string, and all the other strings for all the other integers. Then I want the sum of all the INSTR so the result is one number. So lets say I have int x, and list y=[y0, y1, y2]. I want to do 3 INSTR commands like SUM(INSTR(string for x, string for y0), INSTR(string for x, string for y1), INSTR(string for x, string for y2)) I think im going in the wrong direction, this is what I have. Im not good with sub queries. SELECT SUM ( SELECT INSTR ( SELECT string FROM pages WHERE int=? LIMIT 1, ( SELECT string FROM pages WHERE id=? OR id=? OR id=? LIMIT 3 ) ) )

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  • PIVOT not performing as expected.

    - by Matt W
    Sorry for an unclear question previously; hopefully I can start again... I have this data: entityid name stringvalue ----------- -------------------- -------------------- 1 ShortDescription Coal 1 LongDescription BlackCoal 1 ShortDescription Gold 1 LongDescription WhiteGold 1 ShortDescription Steel 1 LongDescription StainlessSteel And this query: select * from ( select entityid, name, stringvalue as stringvalue from mytable ) as d pivot ( min([stringvalue]) for [name] in ([ShortDescription],[LongDescription]) ) as p Producing this output: entityid ShortDescription LongDescription -------- ---------------- --------------- 1 Coal BlackCoal Could someone tell me why the other rows are not being produced, please? I was expecting to see: entityid ShortDescription LongDescription -------- ---------------- --------------- 1 Coal BlackCoal 1 Gold WhiteGold 1 Steel StainlessSteel Thanks, Matt

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  • Comparison operators not supported for type IList when Paging data in Linq to Sql

    - by Dan
    I can understand what the error is saying - it can't compare a list. Not a problem, other than the fact that I don't know how to not have it compare a list when I want to page through a model with a list as a property. My Model: Event : IEvent int Id string Title // Other stuff.. LazyList<EventDate> Dates // The "problem" property Method which pages the data (truncated): public JsonResult JsonEventList(int skip, int take) { var query = _eventService.GetEvents(); // Do some filtering, then page data.. query = query.Skip(skip).Take(take); return Json(query.ToArray()); } As I said, the above is truncated quite a bit, leaving only the main point of the function: filter, page and return JSON'd data. The exception occurs when I enumerate (.ToArray()). The Event object is really only used to list the common objects of all the event types (Meetings, Birthdays, etc - for example). It still implements IEvent like the other types, so I can't just remove the LazyList<EventDate> Dates' property unless I no longer implementIEvent` Anyway, is there a way to avoid this? I don't really want to compare a LazyList when I page, but I do not know how to resolve this issue. Thank you in advance! :)

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  • LINQ to SQL associations - how to change the value of associated field

    - by HAdes
    I have 2 classes with a LINQ association between them i.e.: Table1: Table2: ID ID Name Description ForiegnID The association here is between Table1.ID - Table2.ForiegnID I need to be able to change the value of Table2.ForiegnID, however I can't and think it is because of the association (as when I remove it, it works). Therefore, does anyone know how I can change the value of the associated field Table2.ForiegnID? Thanks.

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  • SQL - Multiple join conditions using OR?

    - by Brandi
    I have a query that is using multiple joins. The goal is to say "Out of table A, give me all the customer numbers in which you can match table A's EmailAddress with either email_to or email_from of table B. Ignore nulls, internal emails, etc.". It seems like it would be better to use an or condition in the join than multiple joins since it is the same table. When I try to use AND/OR it does not give the behaviour I expect... AND finishes in a reasonable time, but yields no results (I know that there are matches, so it must be some flaw in my logic) and OR never finishes (I have to kill it). Here is example code to illustrate the question: --my original query SELECT DISTINCT a.CustomerNo FROM A a WITH (NOLOCK) LEFT JOIN B e WITH (NOLOCK) ON a.EmailAddress = e.email_from RIGHT JOIN B f WITH (NOLOCK) ON a.EmailAddress = f.email_to WHERE a.EmailAddress NOT LIKE '%@mydomain.___' AND a.EmailAddress IS NOT NULL AND (e.email_from IS NOT NULL OR f.email_to IS NOT NULL) Here is what I tried, (I am attempting logical equivalence): SELECT DISTINCT a.CustomerNo FROM A a WITH (NOLOCK) LEFT JOIN B e WITH (NOLOCK) ON a.EmailAddress = e.email_from OR a.EmailAddress = e.email_to WHERE a.EmailAddress NOT LIKE '%@mydomain.___' AND a.EmailAddress IS NOT NULL AND (e.email_from IS NOT NULL OR e.email_to IS NOT NULL) So my question is two-fold: Why does having AND in the above query work in a few seconds and OR goes for minutes and never completes? What am I missing to make a logically equivalent statement that has only one join?

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  • linq to sql loadwith vs associatewith

    - by stackoverflowuser
    what is the difference between loadwith and associatewith. From the articles i read it seems that loadwith is used to load addition data (eg all orders for the customers). While AssociateWith is used to filter data. Is that a correct understanding? Also it will be nice if someone can explain this with an example based explanation.

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  • When does a query/subquery return a NULL and when no value at all?

    - by AspOnMyNet
    a) If a query/subquery doesn’t find any matching rows, then it either returns NULL or no value at all, thus not even a NULL value. Based on what criteria does a query/subquery return a NULL and when doesn’t it return any results, not even a NULL value? b) I assume a scalar subquery will always return NULL, when no matching rows are found? I assume most-outer scalar query also returns NULL if no rows are found? c) SELECT FirstName, LastName, YEAR(BirthDate) FROM Persons WHERE YEAR(BirthDate) IN (SELECT YearReleased FROM Albums); If subquery finds no results, is then a WHERE clause of an outer query translated into WHERE YEAR(BirthDate) IN (null); ? If instead WHERE clause is translated into WHERE YEAR(BirthDate) IN(); then shouldn’t that be an error condition, since how can YEAR(BirthDate) value be compared to nothing? thanx

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  • cannot read multiple rows from sqldatareader

    - by amby
    Hi, when i query for only one record/row, sqldatareader is giving correct result but when i query for multiple rows, its giving error on the client side. below is my code. please tell me what is the problem here. string query = "select * from Customer_Order where orderNumber = " + order;//+" OR orderNumber = 17"; DataTable dt = new DataTable(); Hashtable sendData = new Hashtable(); try { using (SqlConnection conn = new SqlConnection(ConnectionString)) { using (SqlCommand cmd = new SqlCommand(query, conn)) { conn.Open(); SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection); dt.Load(dr); } }

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  • copy entire row (without knowing field names)

    - by Todd Webb
    Using SQL Server 2008, I would like to duplicate one row of a table, without knowing the field names. My key issue: as the table grows and mutates over time, I would like this copy-script to keep working, without me having to write out 30+ ever-changing fields, ugh. Also at issue, of course, is IDENTITY fields cannot be copied. My code below does work, but I wonder if there's a more appropriate method than my thrown-together text string SQL statement? So thank you in advance. Here's my (yes, working) code - I welcome suggestions on improving it. Todd alter procedure spEventCopy @EventID int as begin -- VARS... declare @SQL varchar(8000) -- LIST ALL FIELDS (*EXCLUDE* IDENTITY FIELDS). -- USE [BRACKETS] FOR ANY SILLY FIELD-NAMES WITH SPACES, OR RESERVED WORDS... select @SQL = coalesce(@SQL + ', ', '') + '[' + column_name + ']' from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'EventsTable' and COLUMNPROPERTY(OBJECT_ID('EventsTable'), COLUMN_NAME, 'IsIdentity') = 0 -- FINISH SQL COPY STATEMENT... set @SQL = 'insert into EventsTable ' + ' select ' + @SQL + ' from EventsTable ' + ' where EventID = ' + ltrim(str(@EventID)) -- COPY ROW... exec(@SQL) -- REMEMBER NEW ID... set @EventID = @@IDENTITY -- (do other stuff here) -- DONE... -- JUST FOR KICKS, RETURN THE SQL STATEMENT SO I CAN REVIEW IT IF I WISH... select EventID = @EventID, SQL = @SQL end

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  • c# - SQL - speed up code to DB

    - by user228058
    I have a page with 26 sections - one for each letter of the alphabet. I'm retrieving a list of manufacturers from the database, and for each one, creating a link - using a different field in the Database. So currently, I leave the connection open, then do a new SELECT by each letter, WHERE the Name LIKE that letter. It's very slow, though. What's a better way to do this? TIA

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  • SQL Server 2008 Dead lock issue

    - by user173552
    I got into a deadlock issue where I am struggling find the root-cause...The Deadlock graph suggests that an UPDATE statement became the victim over a SELECT statement... What puzzles me is that the UPDATE statement is trying to acquire an index on some other table that is never referred in update statement... This is how my UPDATE statement looks like... UPDATE Table set col1 = @P1 where col2 = @P2 This statement acquired a X lock on the col2 index, but also tries to acquire an index on a column defined in some other table that is no way related to the UPDATE statement... And the SELECT statement that won the deadlock situation had nothing to do with the table or index in the update statement but tried to acquire an index on the table in UPDATE statement. eventually causing the DEADLOCK.

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  • LINQ to SQL: making a "double IN" query crashes

    - by Alex
    I need to do the following thing: var a = from c in DB.Customers where (from t1 in DB.Table1 where t1.Date >= DataTime.Now select t1.ID).Contains(c.ID) && (from t2 in DB.Table2 where t2.Date >= DataTime.Now select t2.ID).Contains(c.ID) select a It doesn't want to run. I get the following error: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. But when I try to run var a = from c in DB.Customers where (from t1 in DB.Table1 where t1.Date >= DataTime.Now select t1.ID).Contains(c.ID) select a OR var a = from c in DB.Customers where (from t2 in DB.Table2 where t2.Date = DataTime.Now select t2.ID).Contains(c.ID) select a It works! I'm sure that there both IN queries contain some customers ids.

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  • SQL SELECT Statment

    - by mouthpiec
    Hi, I have a table with the following columns id, teamA_id, teamB_id Will it be possible to a SELECT statement that gives both teamA_id and teamB_id in the same column?

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  • Using AVG() in Oracle SQL

    - by Viet Anh
    I have a table named Student as followed: CREATE TABLE "STUDENT" ( "ID" NUMBER(*,0), "NAME" VARCHAR2(20), "AGE" NUMBER(*,0), "CITY" VARCHAR2(20), PRIMARY KEY ("ID") ENABLE ) I am trying to get all the records of the students having a larger age than the average age. This is what I tried: SELECT * FROM student WHERE age > AVG(age) and SELECT * FROM student HAVING age > AVG(age) Both ways did not work!

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  • SQL Update to the SUM if it's joined values

    - by CL4NCY
    Hi, I'm trying to update a field in the database to the sum of it's joined values: UPDATE P SET extrasPrice = SUM(E.price) FROM dbo.BookingPitchExtras AS E INNER JOIN dbo.BookingPitches AS P ON E.pitchID = P.ID AND P.bookingID = 1 WHERE E.[required] = 1 When I run this I get the following error: "An aggregate may not appear in the set list of an UPDATE statement." Any ideas?

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  • Why can't I shrink a transaction log file, even after backup?

    - by Jordan Hudson
    I have a database that has a 28gig transaction log file. Recovery mode is simple. I just took a full backup of the database, and then ran both: backup log dbmcms with truncate_only DBCC SHRINKFILE ('Wxlog0', TRUNCATEONLY) The name of the db is db_mcms and the name of the transaction log file is Wxlog0. Neither has helped. I'm not sure what to do next.

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  • inserting number into oracle sql - using jython

    - by kdev
    I have this insert command where iam trying to insert a number to be taken from loop i=0 for line in column: myStmt.executeQuery("INSERT INTO REVERSE_COL ( TABLE_NAME,COL_NAME,POS) values (,'test','"+column[i]+"','"+i+"'") i=i+1 POS IS NUMBER DATATYPE but it works if i hard code as 1 i=0 for line in column: myStmt.executeQuery("INSERT INTO REVERSE_COL ( TABLE_NAME,COL_NAME,POS) values (,'test','"+column[i]+"',1") I have tried only i , +i+ and other method but its not working any suggestion how to solve this . Thanks everyone .

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  • When should I open and close a connection to SQL Server

    - by Martin
    I have a simple static class with a few methods in it. Each of those methods open a SqlConnection, query the database and close the connection. This way, I am sure that I always close the connection to the database, but on the other hand, I don't like to always open and close connection. Below is an example of what my methods look like. public static void AddSomething(string something) { using (SqlConnection connection = new SqlConnection("...")) { connection.Open(); // ... connection.Close(); } } Considering that the methods are inside a static class, should I have a static member containing a single SqlConnection? How and when should I drop it? What are the best practices?

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  • SQL Query Math Gymnastics

    - by keruilin
    I have two tables of concern here: users and race_weeks. User has many race_weeks, and race_week belongs to User. Therefore, user_id is a fk in the race_weeks table. I need to perform some challenging math on fields in the race_weeks table in order to return users with the most all-time points. Here are the fields that we need to manipulate in the race_weeks table. races_won (int) races_lost (int) races_tied (int) points_won (int, pos or neg) recordable_type(varchar, Robots can race, but we're only concerned about type 'User') Just so that you fully understand the business logic at work here, over the course of a week a user can participate in many races. The race_week record represents the summary results of the user's races for that week. A user is considered active for the week if races_won, races_lost, or races_tied is greater than 0. Otherwise the user is inactive. So here's what we need to do in our query in order to return users with the most points won (actually net_points_won): Calculate each user's net_points_won (not a field in the DB). To calculate net_points, you take (1000 * count_of_active_weeks) - sum(points__won). (Why 1000? Just imagine that every week the user is spotted a 1000 points to compete and enter races. We want to factor-out what we spot the user because the user could enter only one race for the week for 100 points, and be sitting on 900, which we would skew who actually EARNED the most points.) This one is a little convoluted, so let me know if I can clarify further.

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