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  • How would I associate a "Note" class to 4+ classes without creating lookup table for each associatio

    - by Gthompson83
    Im creating a project tasklist application. I have project, section, task, issue classes, and would like to use one class to be able to add simple notes to any object instance of those classes. The task, issue tables both use a standard identity field as a primary key. The section table has a two field primary key. The project table has a single int primary key defined by the user. Is there a way to associate the note class with each of these without using a seperate lookup table for each class? I'm not so sure my original idea is a decent way to implement this. I considered the following (each variable mapping to a field n the notes table. Private _NoteId As Integer Private _ProjectId As Integer Private _SectionId As Integer Private _SectionId2 As Integer Private _TaskId As Integer Private _IssueId As Integer Private _Note As String Private _UserId As Guid Then I would be able to write seperate methods (getProjectNotes, getTaskNotes) to get notes attached to each class. I started writing this a few weeks ago but got pulled away before i could finish. When revisiting this code today my first thought "this is retarded". Thoughts on drawbacks to this design?

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  • SELECT only a certain set of rows at a time

    - by prmatta
    I need to select data from one table and insert it into another table. Currently the SQL looks something like this: INSERT INTO A (x, y, z) SELECT x, y, z FROM B b WHERE ... However, the SELECT is huge, resulting in over 2 millions rows and we think it is taking up too much memory. Informix, the db in this case, runs out of virtual memory when the query is run. How would I go about selecting and inserting a set of rows (say 2000)? Given that I don't think there are any row ids etc.

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  • Advice on setting up a central db with master tables for web apps

    - by Dragn1821
    I'm starting to write more and more web applications for work. Many of these web applications need to store the same types of data, such as location. I've been thinking that it may be better to create a central db and store these "master" tables there and have each applicaiton access them. I'm not sure how to go about this. Should I create tables in my application's db to copy the data from the master table and store in the app's table (for linking with other app tables using foreign keys)? Should I use something like a web service to read the data from the master table instead of firing up a new db connection in my app? Should I forget this idea and just store the data within my app's db? I would like to have data such as the location central so I can go to one table and add a new location and the next time someone needs to select a location from one of the apps, the new one would be there. I'm using ASP.NET MVC 1.0 to build the web apps and SQL 2005 as the db. Need some advice... Thanks!

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  • How to configure DB connection in a Servlet based JPA application

    - by deamon
    By default DB connections of JPA applications are configured in the META-INF/persistence.xml, when the application is not deployed to a full Java EE application server. In my opinion it is not very elegant to place such environment specific configuration into a file that is inside a .war file. How could a DB connection of a Servlet based JPA application be configured more flexible (=outside of the .war file)?

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  • How do I avoid a race condition in my Rails app?

    - by Cathal
    Hi, I have a really simple Rails application that allows users to register their attendance on a set of courses. The ActiveRecord models are as follows: class Course < ActiveRecord::Base has_many :scheduled_runs ... end class ScheduledRun < ActiveRecord::Base belongs_to :course has_many :attendances has_many :attendees, :through => :attendances ... end class Attendance < ActiveRecord::Base belongs_to :user belongs_to :scheduled_run, :counter_cache => true ... end class User < ActiveRecord::Base has_many :attendances has_many :registered_courses, :through => :attendances, :source => :scheduled_run end A ScheduledRun instance has a finite number of places available, and once the limit is reached, no more attendances can be accepted. def full? attendances_count == capacity end attendances_count is a counter cache column holding the number of attendance associations created for a particular ScheduledRun record. My problem is that I don't fully know the correct way to ensure that a race condition doesn't occur when 1 or more people attempt to register for the last available place on a course at the same time. My Attendance controller looks like this: class AttendancesController < ApplicationController before_filter :load_scheduled_run before_filter :load_user, :only => :create def new @user = User.new end def create unless @user.valid? render :action => 'new' end @attendance = @user.attendances.build(:scheduled_run_id => params[:scheduled_run_id]) if @attendance.save flash[:notice] = "Successfully created attendance." redirect_to root_url else render :action => 'new' end end protected def load_scheduled_run @run = ScheduledRun.find(params[:scheduled_run_id]) end def load_user @user = User.create_new_or_load_existing(params[:user]) end end As you can see, it doesn't take into account where the ScheduledRun instance has already reached capacity. Any help on this would be greatly appreciated.

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  • Does this query fetch unnecessary information? Should I change the query?

    - by Camran
    I have this classifieds website, and I have about 7 tables in MySql where all data is stored. I have one main table, called "classifieds". In the classifieds table, there is a column called classified_id. This is not the PK, or a key whatsoever. It is just a number which is used for me to JOIN table records together. Ex: classifieds table: fordon table: id => 33 id => 12 classified_id => 10 classified_id => 10 ad_id => 'bmw_m3_92923' This above is linked together by the classified_id column. Now to the Q, I use this method to fetch all records WHERE the column ad_id matches any of the values inside an array, called in this case $ad_arr: SELECT mt.*, fordon.*, boende.*, elektronik.*, business.*, hem_inredning.*, hobby.* FROM classified mt LEFT JOIN fordon ON fordon.classified_id = mt.classified_id LEFT JOIN boende ON boende.classified_id = mt.classified_id LEFT JOIN elektronik ON elektronik.classified_id = mt.classified_id LEFT JOIN business ON business.classified_id = mt.classified_id LEFT JOIN hem_inredning ON hem_inredning.classified_id = mt.classified_id LEFT JOIN hobby ON hobby.classified_id = mt.classified_id WHERE mt.ad_id IN ('$ad_arr')"; Is this good or would this actually fetch unnecessary information? Check out this Q I posted couple of days ago. In the comments HLGEM is commenting that it is wrong etc etc. What do you think? http://stackoverflow.com/questions/2782275/another-rookie-question-how-to-implement-count-here Thanks

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  • How should I migrate DDL changes from one environment to the next?

    - by Rl
    I make DDL changes using SQL Developer's GUI. Problem is, I need to apply those same changes to the test environment. I'm wondering how others handle this issue. Currently I'm having to manually write ALTER statements to bring the test environment into alignment with the development environment, but this is prone to error (doing the same thing twice). In cases where there's no important data in the test environment I usually just blow everything away, export the DDL scripts from dev and run them from scratch in test. I know there are triggers that can store each DDL change, but this is a heavily shared environment and I would like to avoid that if possible. Maybe I should just write the DDL stuff manually rather than using the GUI?

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  • Mysql query question

    - by brux
    I have 2 tables: Customer: customerid - int, pri-key,auto fname - varchar sname -varchar housenum - varchar street -varchar Items: itemid - int,pri-key,auto type - varchar collectiondate - date releasedate - date customerid - int I need a query which will get me all items that have a releasedate 3 days prior to (and including) the current date. i.e The query should return customerid,fname,sname,street,housenum,type,releasedate for all items which have releasedate within (and including)3 days prior today thanks in advance

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  • How to use multiple identity numbers in one table?

    - by vincer
    I have an web application that creates printable forms, these forms have a unique number on them, the problem is I have 2 forms that separate numbers need to be created for them. ie) Form1- Numbered 2000000-2999999 Form2- Numbered 3000000-3999999 dbo.test2 - is my form information table Tsel - is my autoinc table for the 3000000 series numbers Tadv - is my autoinc table for the 2000000 series numbers What I have done is create 2 tables with just autoinc row (one for 2000000 series numbers and one for 3000000 series numbers), I then created a trigger to add a record to the coresponding table, read back the autoinc number and add it to my table that stores the form information including the just created autoinc number for the right series of forms. Although it does work, I'm concerned that the numbers will get messed up under load. I'm not sure the @@IDENTITY will always return the right value when many people are using the system. (I cannot have duplicates and I need to use the numbering form show above. See code below. ** TRIGGER ** CREATE TRIGGER MAKEANID2 ON dbo.test2 AFTER INSERT AS SET NOCOUNT ON declare @someid int declare @someid2 int declare @startfrom int declare @test1 varchar(10) select @someid=@@IDENTITY select @test1 = (Select name1 from test2 where sysid = @someid ) if @test1 = 'select' begin insert into Tsel Default values select @someid2 = @@IDENTITY end if @test1 = 'adv' begin insert into Tadv Default values select @someid2 = @@IDENTITY end update test2 set name2=(@someid2) where sysid = @someid SET NOCOUNT OFF

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  • mysql circular dependency in foreign key constraints

    - by Flavius
    Given the schema: What I need is having every user_identities.belongs_to reference an users.id. At the same time, every users has a primary_identity as shown in the picture. However when I try to add this reference with ON DELETE NO ACTION ON UPDATE NO ACTION, MySQL says #1452 - Cannot add or update a child row: a foreign key constraint fails (yap.#sql-a3b_1bf, CONSTRAINT #sql-a3b_1bf_ibfk_1 FOREIGN KEY (belongs_to) REFERENCES users (id) ON DELETE NO ACTION ON UPDATE NO ACTION) I suspect this is due to the circular dependency, but how could I solve it (and maintain referential integrity)?

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  • MySql - set of time stamped data (timestamp,event) calculating events per day

    - by Kevin Ohashi
    I have a table: id, datetime, event i also have table dates: date (Y-m-d format) the problem is some days don't have any events, I would like them to show 0 (or null) SELECT DATE_FORMAT(table.timestamp, '%Y-%m-%d') ydm, count(table.fkUID) FROM `table` where table.fkUID=$var group by ydm; is there some way to join or use conditional statements to make the result show: date|count ---------- 2010-05-23| 5 2010-05-24| 0 <--- this line just doesn't exist in my query. 2010-05-26| 3

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  • Referencing surrogate key

    - by Arman
    I have a table that has an autoincrement surrogate key. I want to use it as a foreign key of my other table. The thing is, I cant figure out how I can reference it to that table, because it is nearly impossible to determine what I have to reference(the actual value of the surrogate key). Please be noted that what I am trying to do is adding a tuple/record through my program(outside the dbms). The process is: Add a new record in Table1 and generate an autoincrement key. Update Add a new record in Table2 and reference its foreign key to the primary key of Table1. Update My question is : HOW do I store the foreign key if I didnt know what is it?

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  • How to Deal with SET ANSI_NULLS ON or OFF ?

    - by Shantanu Gupta
    I want to call this procedure that sends one value that can be NULL or any int value. SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId =@SubDomainId I simply want to use this single query rather than what i m doing right now in below given code. I searched for this how could i do this then i got this Link. According to this I have to set ANSI_NULLS OFF I am not able to set this inside this procedure before executing my sql query and then reset it again after doing this. ALTER PROCEDURE [Tags].[spOnlineTest_SubDomainSelect] @SubDomainId INT AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; -- Insert statements for procedure here IF @SubDomainId IS NULL SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId IS NULL ELSE SELECT DomainName, DomainCode FROM Tags.tblDomain WHERE SubDomainId =@SubDomainId END What will be the better practice to do deal with ANSI_NULLS or Using If Else

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  • SQL - get latest records from table where field is unique

    - by 89stevenharris
    I have a table of data as follows id status conversation_id message_id date_created 1 1 1 72 2012-01-01 00:00:00 2 2 1 87 2012-03-03 00:00:00 3 2 2 95 2012-05-05 00:00:00 I want to get all the rows from the table in date_created DESC order, but only one row per conversation_id. So in the case of the example data above, I would want to get the rows with id 2 and 3. Any advice is much appreciated.

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  • Solr automatic startup script

    - by Camran
    I have followed this tutorial: http://wiki.apache.org/solr/SolrJetty But I cant get it working. I don't know what to put in the etc/defaults/jetty file Does anybody know how to configure this? I have Ubuntu 9 Server. Thanks

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  • Using a variable derived from a drop-down list as the column name in a select statement ... Access DB

    - by user1459698
    I'm working with the world's worst DB that was already here so don't blame me for that. So, here's what I have so far ... module = txtModule.value presstype = txtPressType.value SQL_query = "SELECT * FROM tbl_spareparts WHERE '"& module &"' <> '""' AND '"& module &"' = '"& presstype &"' AND Manufacturer = '"& txtsrch.value &"' ORDER BY SAP_Part_No" Set rsData = conn.Execute(SQL_query) This brings up the following SQL statement: SELECT * FROM tbl_spareparts WHERE 'Banyan_Module' <> '"' AND 'Banyan_Module' = 'PB' AND Manufacturer = 'Tester' ORDER BY SAP_Part_No Is there any way I can use the module variable as a column name - obviously the ''s around the column name are causing an error. This is really bothering me. BTW, I'm writing this in VBScript inside a .HTA application page as it has to run locally on tech PCs. Thanks. R.

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  • How to Auto-Increment Non-Primary Key? - SQL Server

    - by user311509
    CREATE TABLE SupplierQuote ( supplierQuoteID int identity (3504,2) CONSTRAINT supquoteid_pk PRIMARY KEY, PONumber int identity (9553,20) NOT NULL . . . CONSTRAINT ponumber_uq UNIQUE(PONumber) ); The above ddl produces an error: Msg 2744, Level 16, State 2, Line 1 Multiple identity columns specified for table 'SupplierQuote'. Only one identity column per table is allowed. How can i solve it? I want PONumber to be auto-incremented.

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  • Should I sanitize EVERY form variable passed along?

    - by Camran
    I have a form with many fields... The action is set to a php page which queries mysql... Should I sanitize with mysql_real_escape_string every single variable? Or can I ignore sanitizing drop-lists and radios for instance? Also, besides mysql_real_escape_string, what else should I do to prevent attacks? Thanks

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  • How to load the SQL data into several ComboBox easily, am i doing the correctly or is there another way

    - by Dominic Deepan.d
    I have a Combobox to fill the data for City, State and PinCode these combobox is dopdown list and the user will pick it. and it loads once the form opens. Here is the CODE: /// CODE TO BRING A DATA FROM SQL INTO THE FORM DROP LIST /// To fill the sates from States Table cn = new SqlConnection(@"Data Source=Nick-PC\SQLEXPRESS;Initial Catalog=AutoDB;Integrated Security=True"); cmd= new SqlCommand("select * from TblState",cn); cn.Open(); SqlDataReader dr; try { dr = cmd.ExecuteReader(); while (dr.Read()) { SelectState.Items.Add(dr["State"].ToString()); } } catch (Exception ex) { MessageBox.Show(ex.Message); } finally { cn.Close(); } //To fill the Cities from City Table cn1 = new SqlConnection(@"Data Source=Nick-PC\SQLEXPRESS;Initial Catalog=AutoDB;Integrated Security=True"); cmd1 = new SqlCommand("SELECT * FROM TblCity", cn); cn.Open(); SqlDataReader ds; try { ds = cmd1.ExecuteReader(); while (ds.Read()) { SelectCity.Items.Add(ds["City"].ToString()); } } catch (Exception ex) { MessageBox.Show(ex.Message); } finally { cn1.Close(); } // To fill the Data in the Pincode from the City Table cn2 = new SqlConnection(@"Data Source=Nick-PC\SQLEXPRESS;Initial Catalog=AutoDB;Integrated Security=True"); cmd2 = new SqlCommand("SELECT (Pincode) FROM TblCity ", cn2); cn2.Open(); SqlDataReader dm; try { dm = cmd2.ExecuteReader(); while (dm.Read()) { SelectPinCode.Items.Add(dm["Pincode"].ToString()); } } catch (Exception ex) { MessageBox.Show(ex.Message); } finally { cn2.Close(); } its kinda Big, i am doing the same steps for all the combo-box, but is there a way i can merge it in a simple way.

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  • drawbacks of storing all ''things' in a central table

    - by naiquevin
    Hi, I am not sure if there is a term to describe this, but I have observed that content management systems store all kinds of data in a single table with their bare minimum properties while the meta data is stored in another table in form of key value pairs. for eg. everything (blog posts, pages, images, events etc) is stored in one table and considered as a post. I understand that this allows for abstraction and easy extensibility we are considering designing our new project this way. It is not exactly a CMS but we plan to keep adding modules to it in stages. Lets say initially there will be only posts and images on which comments can be posted. Later on we might add videos which will also have the commenting feature. what are the drawbacks of this approach ? and will it work for a requirement like ours ? Thanks

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  • I need a mechanism for locating SQL server instances

    - by SzamDev
    Hi I have an idea and I want to apply it to my Application (C# .NET). When we connect to a DB (MS SQL Server 2008) in VS 2008, the ConnectionString saved in the Application Setting and it's a static varriable (no one can edit it unless you edit it inside VS 2008). I want a way to let my Application search for MS SQL Server and save it to Application Setting and use it to connect to my DB Programmatically. When my application start, the first thing to do is checking the ConnectionString if vaild, NOT Empty and test connection to MS SQL Server Successfully so if there is a proplem I think to show a window form to let the user enter some data like username and password for MS SQL Server 2008 Is there any way to do it?

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  • Why should I abstract my data layer?

    - by Gazillion
    OOP principles were difficult for me to grasp because for some reason I could never apply them to web development. As I developed more and more projects I started understanding how some parts of my code could use certain design patterns to make them easier to read, reuse, and maintain so I started to use it more and more. The one thing I still can't quite comprehend is why I should abstract my data layer. Basically if I need to print a list of items stored in my DB to the browser I do something along the lines of: $sql = 'SELECT * FROM table WHERE type = "type1"';' $result = mysql_query($sql); while($row = mysql_fetch_assoc($result)) { echo '<li>'.$row['name'].'</li>'; } I'm reading all these How-Tos or articles preaching about the greatness of PDO but I don't understand why. I don't seem to be saving any LoCs and I don't see how it would be more reusable because all the functions that I call above just seem to be encapsulated in a class but do the exact same thing. The only advantage I'm seeing to PDO are prepared statements. I'm not saying data abstraction is a bad thing, I'm asking these questions because I'm trying to design my current classes correctly and they need to connect to a DB so I figured I'd do this the right way. Maybe I'm just reading bad articles on the subject :) I would really appreciate any advice, links, or concrete real-life examples on the subject!

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  • dymanic columns in mysql tables?

    - by fayer
    i want to add dynamic columns in a mysql table. but i dont know exactly how. i want to let the user add some columns (fields) in a thread. eg. let him add a integer field and a value (eg. price: 199) or a string field and a value (eg. name: teddybear). the user can add as many field/value-pairs as he wants. i thought i could create a many-to-many table: thread <- thread_field <- field thread: id, title thread_field: field_id, thread_id, value field: id, name is this a good structure? but in this way i have to set a specific column type of thread_field.value. either its an integer or a string. i want to have the possibility to have it dymanic, let the user choose. how can i do this? thanks!

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