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  • antlr: Best practice to integrate generated parser into the system

    - by green
    Here is the background, I am trying to create a DSL to allow customer write simple scripts to query into our mongodb based database. I choose antlr to implement the DSL. From my understanding (and pls let me know if it's not correct) there are 2 approaches to integrate antlr generated parser into the system: Embed code into the grammar file so that the generated parser could be used directly to make query to the database and return result in a certain format (e.g. json encoded) Keep the parser purely a parser, after feed the DSL file to it, and construct the query in another class by retrieving the AST from generated parser class So antlrers, which one do you think is the way I as an antlr newbie should go? Can you list the pros and cos of each approach, or you have other way to recommend?

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  • How can an SQL query return data from multiple tables

    - by Fluffeh
    I would like to know how to get data from multiple tables in my database, what types of methods are there to do this, what are joins and unions and how are they different from one another? When should I use each one compared to the others? I am planning to use this in my (for example - PHP) application, but don't want to run multiple queries against the database, what options do I have to get data from multiple tables in a single query? Note: I am writing this as I would like to be able to link to a well written guide on the numerous questions that I constantly come across in the PHP queue, so I can link to this for further detail when I post an answer. The answers cover off the following: Part 1 - Joins and Unions Part 2 - Subqueries Part 3 - Tricks and Efficient Code

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  • How to persist every new entity?

    - by simpatico
    I expect every instantiated entity to correspond to a tuple (& co) in the database. In the examples I see around, one always instantiates the entity (via a constructor) and then calls persist with that entity. I find this error-prone, and was wondering if it wasn't possible to have every instantiated entity automatically managed/persisted/reflected to the database (at least intended to). This also seems to prevent me from persisting instance variable entities. I.e. I've an entity which instantiates another (entities it has an association with) in its constructor.

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  • Need help with Excel 2007 Formula - Many to many update

    - by Monica
    I'm experienced with database development, but not so much with Excel. I'm looking for help writing an Excel formula that would help my client's spreadsheet behave like a database. This is what I'm looking to do, but I can't figure out how to write it in Excel 2007: "If Q4 (on sheet 2) contains A2 (on sheet 1), append A1 (on sheet 1) with Q5 (on sheet 2)" Some factors: 1) This formula may find multiple instances of A2, so it should not stop after finding the first match 2) The values, as they are created in A1, should be separated with comma and space 3) This is a many to many relationship between Q4 and A2 Thanks for any help with this. I've tried vlookups, match, if statements, but they all fall short in one way or another.

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  • Using ExecuteQuery() with entity framework, entity class.

    - by sfreelander
    I am trying to jump from ASP Classic to asp.net. I have followed tutorials to get Entity Framework and LINQ to connect to my test database, but I am having difficulties figuring out ExecuteQuery(). I believe the problem is that I need an "entity class" for my database, but I can't figure out how to do it. Here is my simple code: Dim db as New TestModel.TestEntity Dim results AS IEnumerable(OF ???) = db.ExecuteQuery(Of ???)("Select * from Table1") From the microsoft example site, they use an entity class called Customers, but I don't understand what that means.

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  • Will lock() statement block all threads in the proccess/appdomain?

    - by MikeJ
    Maybe the question sounds silly, but I don't understand 'something about threads and locking and I would like to get a confirmation (here's why I ask). So, if I have 10 servers and 10 request in the same time come to each server, that's 100 request across the farm. Without locking, thats 100 request to the database. If I do something like this: private static readonly object myLockHolder = new object(); if (Cache[key] == null) { lock(myLockHolder) { if (Cache[key] == null) { Cache[key] = LengthyDatabaseCall(); } } } How many database requests will I do? 10? 100? Or as much as I have threads?

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  • How do i find out in sql what db name I'm connect to

    - by gjutras
    We have a change control environment where the developers give scripts to change control people to run. we have dev,qa, & production environments. I want to conditionalize a couple segments to do some different things depending on what database the change control person is running my script. If @dbname='dev' then begin --do some dev stuff end If @dbname='QA' then begin --do some qa stuff end If @dbname='Prod' then begin --do some production stuff end How do I get at what the current connected database is and fill @dbname?

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  • Class design question (Disposable and singleton behavior)

    - by user137348
    The Repository class has singleton behavior and the _db implements the disposable pattern. As excepted the _db object gets disposed after the first call and because of the singleton behavior any other call of _db will crash. [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)] public class Repository : IRepository { private readonly DataBase _db; public Repository(DataBase db) { _db = db; } public int GetCount() { using(_db) { return _db.Menus.Count(); } } public Item GetItem(int id) { using(_db) { return _db.Menus.FirstOrDefault(x=>x.Id == id); } } } My question is, is there any way to design this class to work properly without removing the singleton behavior? The Repositoryclass will be serving big amount of requests.

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  • Parsing a string to date gives 01/01/0001 00:00:00

    - by kawtousse
    String dateimput=request.getParameter("datepicker"); System.out.printl("datepicker:" +dateimput); DateFormat df = new SimpleDateFormat("MM/dd/yyyy"); Date dt = null; try { dt = df.parse(dateimput); System.out.println("date imput is:" +dt); } catch (ParseException e) { e.printStackTrace(); } *datepicker:04/29/2010 (value I currently selected from datepicker). *the field in database is typed date. 1-date imput is:Thu Apr 29 00:00:00 CEST 2010 and in database level it is inserted like that 01/01/0001 00:00:00

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  • Embedded Java Databases for Large Data Sets

    - by ExAmerican
    I would like to port a PHP/MySQL-based client/server application to be a standalone desktop application written in Java. The database has grown to be fairly large, with several tables with hundreds of thousands of rows. I expect these could grow to over a million entries for certain tables. What embedded database would best handle this? HSQLDB and Sqlite seem to be the obvious choices, though I'm guessing there are others out there as well. My main priorities are the ability to perform queries on large amounts of data efficiently (this thread seems to confirm Sqlite can handle this) and the ease with which I can import old data from MySQL (I remember HSQLDB being kind of a pain for that). Note: I am aware that similar questions comparing embedded databases have been posted before (for example here and here) but as my priorities differ somewhat from most applications considering the large data migration I thought it justified a new question.

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  • Using a large list of terms, search through page text and replace words with links

    - by dunc
    A while ago I posted this question asking if it's possible to convert text to HTML links if they match a list of terms from my database. I have a fairly huge list of terms - around 6000. The accepted answer on that question was superb, but having never used XPath, I was at a loss when problems started occurring. At one point, after fiddling with code, I somehow managed to add over 40,000 random characters to our database - the majority of which required manual removal. Since then I've lost faith in that idea and the more simple PHP solutions simply weren't efficient enough to deal with the amount of data and the quantity of terms. My next attempt at a solution is to write a JS script which, once the page has loaded, retrieves the terms and matches them against the text on a page. This answer has an idea which I'd like to attempt. I would use AJAX to retrieve the terms from the database, to build an object such as this: var words = [ { word: 'Something', link: 'http://www.something.com' }, { word: 'Something Else', link: 'http://www.something.com/else' } ]; When the object has been built, I'd use this kind of code: //for each array element $.each(words, function() { //store it ("this" is gonna become the dom element in the next function) var search = this; $('.message').each( function() { //if it's exactly the same if ($(this).text() === search.word) { //do your magic tricks $(this).html('<a href="' + search.link + '">' + search.link + '</a>'); } } ); } ); Now, at first sight, there is a major issue here: with 6,000 terms, will this code be in any way efficient enough to do what I'm trying to do?. One option would possibly be to perform some of the overhead within the PHP script that the AJAX communicates with. For instance, I could send the ID of the post and then the PHP script could use SQL statements to retrieve all of the information from the post and match it against all 6,000 terms.. then the return call to the JavaScript could simply be the matching terms, which would significantly reduce the number of matches the above jQuery would make (around 50 at most). I have no problem with the script taking a few seconds to "load" on the user's browser, as long as it isn't impacting their CPU usage or anything like that. So, two questions in one: Can I make this work? What steps can I take to make it as efficient as possible? Thanks in advance,

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  • Membership with Microsoft Access

    - by sanfra1983
    Hi, I'm doing project in asp.net mvc with Micorsoft Access database and I need to figure out how to make a login system and roles with Microsoft Access. I have seen some examples on the web: [http://binarywater.com/OleDbASPNETMembershipProvider.html][1] [http://imar.spaanjaars.com/QuickDocId.aspx?quickdoc=404][2] I want to understand if they are examples that can be used in asp.nt mvc frmework 1.0 with 3.5. Because the first link talks about asp.net 2.0 and also create the DataBase aspnetDB.mdb how do I use tables in my db? You want to be one of your suggestions Thanks again for your help

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  • Activiti Engine: Task Event - User is null

    - by sockeqwe
    I have a problem, which should be simple to solve, but i can't find the method to call to solve this problem: My problem is, that every Task Event (org.activiti.engine.task.Event) returnes null by calling Event.getUserId(); If I take a look into the database I see that the database table ACT_HI_COMMENT has null as value for the column USER_ID_ for every row. I generate these TaskEvents programmatically by calling (for example) processEngine.getTaskService().addComment(task.getId(), null, commentMessage); processEngine.getTaskService().addUserIdentityLink(task.getId(), user.getId(), IDENTITY_LINK_OBSERVER); I guess there is a simple method that I must call to solve this problem, something like processEngine.setCurrentUser(authenticatedUser.getId()); Any suggestions?

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  • Dynamic SQL queries in code possible?

    - by SeanD
    Instead of hard coding sql queries like Select * from users where user_id =220202 can these be made dynamic like Select * from $users where $user_id = $input. Reason i ask is when changes are needed to table/column names i can just update it in one place and don't have to ask developers to go line by line to find all references to update. It is very time consuming. And I do not like the idea of exposing database stuff in the code. My major concern is load time. Like with dynamic pages, the database has to fetch the page content, same way if queries are dynamic first system has to lookup the references then execute the queries, so does it impact load times? I am using codeignitor PHP. If it it possible then the next question is where to store all the references? In the app, in a file, in the DB, and how?

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  • How to delete unused sequences?

    - by user1023877
    We are using PostgreSQL. My requirement is to delete unused sequences from my database. For example, if I create any table through my application, one sequence will be created, but for deleting the table we are not deleting the sequence, too. If want to create the same table another sequence is being created. Example: table: file; automatically created sequence for id coumn: file_id_seq When I delete the table file and create it with same name again, a new sequence is being created (i.e. file_id_seq1). I have accumulated a huge number of unused sequences in my application database this way. How to delete these unused sequences?

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  • How to use GPS data like the double value returned by getLatitude()?

    - by Dan
    I have been searching quite a bit for an answer, but maybe I'm just not using the correct terminology. I am creating an app that will access a database to return a list of other users that are within a certain distance of the users location. I've never worked with this type of data, and I don't really know what the values mean. I'd like to do all the calculations on the backend with either MySQL or PHP. Currently, I am storing the latitude and longitude as doubles within the database. I can access them and store them, but I have no idea how I might be able to sort them based on distance. Perhaps I should be using a different type or some technique that is common in this area. TIA.

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  • Drupal Error After Logging In

    - by Kim
    Hello everyone. I'm kinda new to using drupal and i'm just wondering why I kind of get this error on my new site. See i have this website under WampServer running drupal6-16. Everytime I log in with my pre-created admin account 'admin01' pass: 'admin01' i get redirected to the WampServer localhost which appears to be unusual since the header does not have the WampServer logo. I already tried creating a new drupal website with the same database and the same thing happens. Also, I tried creating another website with a new database but I copied the other website's theme and other contents and the same thing happens. Help me please. I am losing my grip on this. :( Note: I have the same website running on one PC and i am just trying to run it on another PC by copying all its contents. The original copy is working perfectly but I can't seem to get the hook on my new copies to work on other PCs.

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  • Common optimization rules

    - by mafutrct
    This is a dangerous question, so let me try to phrase it correctly. Premature optimization is the root of all evil, but if you know you need it, there is a basic set of rules that should be considered. This set is what I'm wondering about. For instance, imagine you got a list of a few thousand items. How do you look up an item with a specific, unique ID? Of course, you simply use a Dictionary to map the ID to the item. And if you know that there is a setting stored in a database that is required all the time, you simply cache it instead of issuing a database request hundred times a second. I guess there are a few even more basic ideas. I am specifically not looking for "don't do it, for experts: don't do it yet" or "use a profiler" answers, but for really simple, general hints. If you feel this is an argumentative question, you probably misunderstood my intention.

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  • Unique identification string in php

    - by NardCake
    Currently me and my friend are developing a website, for what we will call 'projects' we just have a basic auto increment id in the database used to navigate to projects such as oururl.com/viewproject?id=1 but we started thinking, if we have alot of posted projects thats going to be a LONG url. So we need to somehow randomly generate a alphanumerical string about 6 characters long. We want the chance of the string being duplicated being extremely low and of course we will query the database before assigning an identifier. Thanks for anyhelp, means alot!

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  • SQL Server 2008 - Conditional Query

    - by Villager
    Hello, SQL is not one of my strong suits. I have a SQL Server 2008 database. This database has a stored procedure that takes in eight int parameters. For the sake of keeping this question focused, I will use one of these parameters for reference: @isActive int Each of these int parameters will be -1, 0, or 1. -1 means "Unknown" or "Don't Care". Basically, I need to query a table such that if the int parameter is NOT -1, I need to consider it in my WHERE clause. Because there are eight int parameters, an IF-ELSE statement does not seem like a good idea. At the same time, I do not know how else to do this? Is there an elegant way in SQL to add a WHERE conditional if a parameter does NOT equal a value? Thank you!

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  • php query cant figure out the problem

    - by Eat
    I dont get an error but it does not return me the row values as well. How can I address the problem? <?php //DATABASE $dbConn = mysql_connect($host,$username,$password); mysql_select_db($database,$dbConn); $SQL = mysql_query("SELECT N.*, C.CatID FROM News N INNER JOIN Categories C ON N.CatID = C.CatID WHERE N.Active = 1 ORDER BY DateEntered DESC"); while ( $Result = mysql_fetch_array($SQL) or die(mysql_error())) { $CatID[] = $Result[CatID]; $NewsName[] = $Result[NewsName]; $NewsShortDesc[] = $Result[NewsShortDesc]; } // mysql_free_result($Result); ?> <div class="toparticle"> <span class="section"><?=$CatID[0] ?> </span> <span class="headline"><?=$NewsName[0] ?></span> <p><?=$NewsShortDesc[0] ?></p> </div>

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  • Batch To Bash Conversion

    - by Steven
    I need to know this Batch Script into Bash : @echo off set /p name= Name? findstr /m "%name%" ndatabase.txt if %errorlevel%==0 ( cls echo The name is found in the database! pause >nul exit ) cls echo. echo Name not found in database. pause >nul exit I am new to the Linux Kernel, so starting off with an easy distro - Ubuntu 12.10. My problem is that I do not really know much of Bash Script, since I am very accustomed to the Batch Script format; which is obviously a bad habit for my C++.

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  • SQL To Filter A SubSet Of Data

    - by Nick LaMarca
    I have an arraylist that holds a subset of names found in my database. I need to write a query to get a count of the people in the arraylist for certain sections i.e. There is a field "City" in my database from the people in the arraylist of names I want to know how many of them live in Chicago, how many live in New York etc. Can someone help me how I might set up an sql statement to handle this. I think somehow I have to pass the subset of names to sql somehow.

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  • Accessing TextView from another class

    - by Jenny
    I've got my main startup class loading main.xml but I'm trying to figure out how to access the TextView from another class which is loading information from a database. I would like to publish that information to the TextView. So far I've not found any helpful examples on Google. EDIT: This is my class that is doing the Database work: import android.widget.TextView;import android.view.View; public class DBWork{ private View view; ... TextView tv = (TextView) view.findViewById(R.id.TextView01); tv.setText("TEXT ME") Yet, everytime I do that I get a nullpointerexception

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  • iPhone SDK: Data Synchronization

    - by buzzappsoftware
    I am looking for an overview of data synchronization techniques available on the iPhone platform. We need the ability to be able to sync a subset of content from a server to a local database residing on the iPhone. On other projects I have worked on, the data synchronization was handled by the database. Is that available in SQLite? If not, any suggestions on techniques? Rolling our own would not be my first choice. Thanks in advance.

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