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• Joining two tables (through a link), one which may yield multiple rows, together into one result.

  - by Eikern

  Lets say I've got a table listing car brands or models: Cars: Id | Brand ----------- 1 | BMW 2 | Audi 3 | Volvo And I've also got another table which links features. Link: Id | carid | featureid ----------------------- 1 | 1 | 1 2 | 1 | 2 3 | 2 | 2 4 | 3 | 1 5 | 3 | 2 6 | 3 | 3 And I've got the table listing the features. Features: Id | Feature ----------- 1 | A/C 2 | 4WD 3 | Heated seats I want to list these results on my front page like this: BMW A/C 4WD Audi 4WD Volvo A/C 4WD Heated seats What's the best/most efficient way of doing this (using PHP and MySQL)?

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• Eager loading in EF1.0

  - by Dave Swersky

  I have a many-to-many relationship: Application - Applications_Servers - Server This is set up in my Entity Data Model and all is well. My problem is that I'd like to eager-load the whole graph of Applications so that I have an IEnumerable<Applications>, each Application member populated with the Servers collection associated by the many-to-many relationship. Normally this wouldn't be a problem, but according to my research there must be a navigation property between Application and Server. This is not the case for me because my Applications_Servers join table has more in it than just the two keys. Therefore, there is no navigation property directly between Application and Server, and this doesn't work: var apps = (from a in context.Application.Include("Server") select a).ToList(); I get an error saying there is no navigation property on Application called "Server", and that's correct, there is none. How do I write the query to eager-load my Applications with their Servers in this case?

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• How cast in c#/.net 3.5 works? for types with '?'

  - by Inez

  This is my code which works public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : (decimal?) null; } and this one doesn't work public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : null; } giving the compilator error: Error 1 Type of conditional expression cannot be determined because there is no implicit conversion between 'decimal' and '' I wonder why? any ideas?

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• How does cast in C#/.NET 3.5 work for types with '?'

  - by Inez

  This is my code which works public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : (decimal?) null; } and this one doesn't work public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : null; } giving the compiler error: Error 1 Type of conditional expression cannot be determined because there is no implicit conversion between 'decimal' and '<null>' I wonder why? any ideas?

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• How to pass a Lambda Expression as method parameter with EF

  - by Registered User

  How do I pass an EF expression as a method argument? To illustrate my question I have created a pseudo code example: The first example is my method today. The example utilizes EF and a Fancy Retry Logic. What I need to do is to encapsulate the Fancy Retry Logic so that it becomes more generic and does not duplicate. In the second example is how I want it to be, with a helper method that accepts the EF expression as an argument. This would be a trivial thing to do with SQL, but I want to do it with EF so that I can benefit from the strongly typed objects. First Example: public static User GetUser(String userEmail) { using (MyEntities dataModel = new MyEntities ()) { var query = FancyRetryLogic(() => { (dataModel.Users.FirstOrDefault<User>(x => x.UserEmail == userEmail))); }); return query; } } Second Example: T RetryHelper<T>(Expression<Func<T, TValue>> expression) { using (MyEntities dataModel = new (MyEntities ()) { var query = FancyRetryLogic(() => { return dataModel.expression }); } } public User GetUser(String userEmail) { return RetryHelper<User>(<User>.FirstOrDefault<User>(x => x.UserEmail == userEmail)) }

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• What is the correct method to load an XML file and re-write it as a CSV? (C# Only)

  - by codesmack

  I have a XML file that I want to load into an unknown object type. (I say unknown object type because I am not sure what direction to go) Once I have the data loaded I need to do some processing on certain elements that are now loaded into the new object. For sake of example, we can say that the xml file is full of elements named <car> and within the car element I need to process the <mileage> element. Then once this is all done I need to write the file as a CSV file. I would like to do this is the most direct way possible. (The less code the better) I am using VS 2008 C#

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• Quickly or concisely determine the longest string per column in a row-based data collection

  - by ccornet

  Judging from the failure of my last inquiry, I need to calculate and preset the widths of a set of columns in a table that is being made into an Excel file. Unfortunately, the string data is stored in a row-based format, but the widths must be calculated in a column-based format. The data for the spreadsheets are generated from the following two collections: var dictFiles = l.Items.Cast<SPListItem>().GroupBy(foo => foo.GetSafeSPValue("Category")).ToDictionary(bar => bar.Key); StringDictionary dictCols = GetColumnsForItem(l.Title); Where l is an SPList whose title determines which columns are used. Each SPListItem corresponds to a row of data, which are sorted into separate worksheets based on Category (hence the dictionary). The second line is just a simple StringDictionary that has the column name (A, B, C, etc.) as a key and the corresponding SPListItme field display name as the corresponding value. So for each Category, I enumerate through dictFiles[somekey] to get all the rows in that sheet, and get the particular cell data using SPListItem.Fields[dictCols[colName]]. What I am asking is, is there a quick or concise method, for any one dictFiles[somekey], to retrieve a readout of the longest string in each column provided by dictCols? If it is impossible to get both quickness and conciseness, I can settle for either (since I always have the O(n*m) route of just enumerating the collection and updating an array whenever strCurrent.Length strLongest.Length). For example, if the goal table was the following... Item# Field1 Field2 Field3 1 Oarfish Atmosphere Pretty 2 Raven Radiation Adorable 3 Sunflower Flowers Cute I'd like a function which could cleanly take the collection of items 1, 2, and 3 and output in the correct order... Sunflower, Atmosphere, Adorable Using .NET 3.5 and C# 3.0.

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• Distinct items from IEnumerable< T>

  - by ScG

  I have an IEnumerable< Person object. The Person class has a Designation proeprty. I want to select distinct Designation values from IEnumerable< Person and assign that to a DropDownList. How can I do it?

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• StreamInsight complex query with filter on HoppingWindow

  - by hh354

  I'm trying out StreamInsight and I came across a problem with a query I need. I'm trying to throw a warning if there are several changes in my measured values (of up to 20% change) in the last 30 minutes. This is the query I came up with for now but it isn't working and it's not even correct I think. Apparently I can't filter on a window...? var deviationQuery = from s in wcfStream group s by s.SensorId into grouped from window in grouped.HoppingWindow(TimeSpan.FromMinutes(30),TimeSpan.FromMinutes(1)) where window.StdDev(e => e.Value) > measurableValue * 1.2 select new OutputEvent { Error = "Deviation" }; Thanks in advance!

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• Getting counts of 0 from a query with a double group by

  - by Maltiriel

  I'm trying to write a query that gets the counts for a table (call it item) categorized by two different things, call them type and code. What I'm hoping for as output is the following: Type Code Count 1 A 3 1 B 0 1 C 10 2 A 0 2 B 13 2 C 2 And so forth. Both type and code are found in lookup tables, and each item can have just one type but more than one code, so there's also a pivot (aka junction or join) table for the codes. I have a query that can get this result: Type Code Count 1 A 3 1 C 10 2 B 13 2 C 2 and it looks like (with join conditions omitted): SELECT typelookup.name, codelookup.name, COUNT(item.id) FROM typelookup LEFT OUTER JOIN item JOIN itemcodepivot RIGHT OUTER JOIN codelookup GROUP BY typelookup.name, codelookup.name Is there any way to alter this query to get the results I'm looking for? This is in MySQL, if that matters. I'm not actually sure this is possible all in one query, but if it is I'd really like to know how. Thanks for any ideas.

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• array insert in db

  - by gloris

  Hi, How best to put the array (100 or more length) in the database (MySQL)? I do not want multiple access to the database because it is so loaded. So my solution is as follows: string insert = "INSERT INTO programs (name, id) VALUES "; for(int i = 0; i < name.Length; i++) { if (i != 0) { insert = insert + ",("; } else { insert = insert + "("; } insert = insert + "'" + name[i] + "','" + id[i] + "'"; insert = insert + ")"; } //INSERT INTO programs (name, id) VALUES ('Peter','32'),('Rikko','343') .... But maybe is a faster version? Thanks

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• Indexed key vs indexed separate columns, which one is faster ?

  - by Jerry

  In MYSQL, from a pure performance perspective, if I have a table with large amount of data with 10/1 read/write ratio. is it faster in read/write performance to have 4 search criteria in separate columns and all indexed or have them combined in to one single string acting as a key and store in one indexed column ? e.g. say this table with 5 columns, first name, last name, sex, country and file where the first four columns will ALWAYS be given as a part of search parameters in a search or have a table with two columns, key and file. where the value of key can be john-smith-male-australia ?? I don't quite get the pros and cons. the point I try to stress is the fact that all parameters will be given.in a search.

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• What is the best way to store categorical references in SQL tables?

  - by jlafay

  I'm wanting to store a wide array of categorical data in MySQL database tables. Let's say that for instance I want to to information on "widgets" and want to categorize attributes in certain ways, i.e. shape category. For instance, the widgets could be classified as: round, square, triangular, spherical, etc. Should these categories be stored within a table to reference them best from an application? Another possibility, I would imagine, would be to add a column to widgets that contained a shape column that contained a tiny int. That way my application could search shapes by that and then use a coordinating enum type that would map the shape int meanings. Which would be best? Or is there another solution that I'm not thinking of yet?

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• Virtual directories as DB queries

  I have a site, e.g. site.com I would like users to be able to access it in their locale at site.com/somecity This is similar to craigslist, but they do it with subdomains e.g. sfbay.craigslist.org Using Apache HTTP server. MySql for DB. If you can provide a brief explanation and perhaps links to more thorough discussions, I would be quite interested in learning. I'm developing a web-app and wonder if I should focus some time to read up on Apache, or should I focus more of my time on server-side programming. Thanks!

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• DataContext to DB

  - by JD

  Hi all, I have designed my DB using the ORM in VS 2008. What is the best way to export this to an SQL server so it will create the tables and relations on SQL Server? Thanks, JD

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• Two-key encryption/decryption?

  - by Matt

  I'm looking to store some fairly sensitive data using PHP and MySQL and will be using some form of reversible encryption to do so since I need to get the data back out in plain text for it to be of any use. I'll be deriving the encryption key from the users' username/password combination but I'm stumped for what to do in the (inevitable) event of a password being forgotten. I realise that the purpose of encryption is that it can only be undone using the correct key but this must have been addressed before.. I'm trying to get my head around whether or not public key cryptography would apply to the problem but all I can think of is that the private key will still need to be correct to decrypt the data.. Any ideas?

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• share image with url from database

  - by LauroSkr

  In my PHP web site will have a text converted to jpeg file,so it is a image. I want that i give users option to share the image. every image will have unique url so they can share image on facebook,twitter , do i need to put images with their url in mysql database or you do it in cloud? user will write text and then script will convert it to image and show it as image. then i want to provide user that he/she can share their created image. It would be great if you could provide me with a link or tutorial for my problem. Dont be hard on beginners,you were all in the same boat.. Thanks, LauroSkr

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• Is there any extension method which get void returning lamda expression ?

  - by Freshblood

  For example int[] Array = { 1, 23, 4, 5, 3, 3, 232, 32, }; Array.JustDo(x => Console.WriteLine(x));

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• HOw do I limit array to a certain number??

  - by mathew

  I do have an array which queries database..what I need to do is control this array to a certain number say 10. but I dont want to set LIMIT in mysql query I need to leave that as it is... $result = mysql_query("SELECT * FROM query ORDER BY regtime DESC"); while($row = mysql_fetch_array($result)) { echo "<img src='bullet.gif' align='absmiddle' class='col1ab'><a class='col1ab' href=".$row['web']." >www.".$row['web']."</a><br>"; } How do I limit this array to certain limit??

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• Caching stored procedure results in Linq'u

  - by itdebeloper

  In our web application we have a lots of stored procedures look like this one: getSomeData(/* 7 diffrent params */) This stored procedure don't make any updates. We are using Linq'u. I know that the date are changing no often than once per day so the results for the same sets of parameters values will be the same. Does Linqu have cache simple solution? I know how to 'manually' write cache mechanism in .net, but I supposed that in Linqu this problem was solved. I'm a lazy guy :) so I'm looking for something realy simple like: Linqu_global_store_procedure_configuration.CacheDuration="600" Linqu_global_store_procedure_configuration.CacheVaryByParam="*" I'm using .net 3.5 but its not any problem to move for 4.0.

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• RODBC string getting truncated

  - by sayan dasgupta

  Hi all, I am fetching data from MySql Server into R using RODBC. So in one column of the database is a character vector SELECT MAX(CHAR_LENGTH(column)) FROM reqtable; RETURNS 26566 Now I will show you an example how I am running into the problem `library(RODBC) con <- odbcConnect("mysqlcon") rslts <- as.numeric(sqlQuery(con, "SELECT CHAR_LENGTH(column) FROM reqtable LIMIT 10", as.is=TRUE)[,1]) ` returns > rslts [1] 62 31 17 103 30 741 28 73 25 357 where as rslts <- nchar(as.character(sqlQuery(con, "SELECT column FROM reqtable LIMIT 10", as.is=TRUE)[,1])) returns > rslts [1] 62 31 17 103 30 255 28 73 25 255 So strings with length 255 is getting truncated at 255. Is there a way I can get the full string. Thanks

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• Approach to data wrapping

  - by Mikhail

  I'm developing in PHP and MySQL. The information about the currently logged in user is stored in many different tables. The information that I need on each page, I preload. However if something is needed from a rarely accessed table - then I do $newdata = $db->Query('SELECT * FROM rare_table WHERE user_id='.$user->id); I would like to simplify the above to a point where I don't have to specify that the query should be limited to this particular user. An ideal function call would be: $newdata = $user->Query('SELECT * FROM rare_table'); Obviously I'd have to parse the SQL and add a WHERE clause. Or add to the already existing clause. Questions: are there tools to do this? How can I develop this? Is this even a good idea?

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• how to debug a query that has valid syntax, executes, but returns no results?

  - by Ty W

  So I'm writing a fairly involved query with a half dozen joins, a dependent subquery for [greatest-n-per-group] purposes, grouping, etc. It is syntactically valid, but I've clearly made at least one mistake because it returns nothing. In the past I've debugged valid queries that return nothing by removing joins, executing subqueries on their own, removing WHERE conditions, and removing grouping to see what I would get but so far this one has me stumped. Are there better tools or techniques to use for this sort of thing? This particular query is for MySQL if it matters for any platform-specific tools.

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• Using strtotime for dates before 1970

  - by ctroy

  I have a text column in mysql and it stores a date value in the format yyyy-mm-dd. Now, in my php page, I use this code to parse into a date value. date("F j, Y", strtotime($row['value'])); Now, I just read that strtotime() parses values only after January 1, 1970. I have lot of date values before that date. Is there a work around? I don't want to change my database structure.

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• SQL LIKE question

  - by user176121

  I was wondering if there's a drawback (other than bad practice) to using something like this SELECT * FROM my_table WHERE id LIKE '1'; where id is an integer. I know you're supposed to use id=1 but I am writing a java program and if everything can use LIKE it'll be a lot easier for me. Also, so far, everything works fine; I get the correct query results, so if there is no drawback I will continue doing it like this. edit: I am using MySQL.

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