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• How to structure the tables of a very simple blog in MySQL?

  - by Programmer

  I want to add a very simple blog feature on one of my existing LAMP sites. It would be tied to a user's existing profile, and they would be able to simply input a title and a body for each post in their blog, and the date would be automatically set upon submission. They would be allowed to edit and delete any blog post and title at any time. The blog would be displayed from most recent to oldest, perhaps 20 posts to a page, with proper pagination above that. Other users would be able to leave comments on each post, which the blog owner would be allowed to delete, but not pre-moderate. That's basically it. Like I said, very simple. How should I structure the MySQL tables for this? I'm assuming that since there will be blog posts and comments, I would need a separate table for each, is that correct? But then what columns would I need in each table, what data structures should I use, and how should I link the two tables together (e.g. any foreign keys)? I could not find any tutorials for something like this, and what I'm looking to do is really offer my users the simplest version of a blog possible. No tags, no moderation, no images, no fancy formatting, etc. Just a simple diary-type, pure-text blog with commenting by other users.

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• Excessive use of Inner Join for more than 3 tables

  - by Archangel08

  Good Day, I have 4 tables on my DB (not the actual name but almost similar) which are the ff: employee,education,employment_history,referrence employee_id is the name of the foreign key from employee table. Here's the example (not actual) data: **Employee** ID Name Birthday Gender Email 1 John Smith 08-15-2014 Male [email protected] 2 Jane Doe 00-00-0000 Female [email protected] 3 John Doe 00-00-0000 Male [email protected] **Education** Employee_ID Primary Secondary Vocation 1 Westside School Westshore H.S SouthernBay College 2 Eastside School Eastshore H.S NorthernBay College 3 Northern School SouthernShore H.S WesternBay College **Employment_History** Employee_ID WorkOne StartDate Enddate 1 StarBean Cafe 12-31-2012 01-01-2013 2 Coffebucks Cafe 11-01-2012 11-02-2012 3 Latte Cafe 01-02-2013 04-05-2013 Referrence Employee_ID ReferrenceOne Address Contact 1 Abraham Lincoln Lincoln Memorial 0000000000 2 Frankie N. Stein Thunder St. 0000000000 3 Peter D. Pan Neverland Ave. 0000000000 NOTE: I've only included few columns though the rest are part of the query. And below are the codes I've been working on for 3 consecutive days: $sql=mysql_query("SELECT emp.id,emp.name,emp.birthday,emp.pob,emp.gender,emp.civil,emp.email,emp.contact,emp.address,emp.paddress,emp.citizenship,educ.employee_id,educ.elementary,educ.egrad,educ.highschool,educ.hgrad,educ.vocational,educ.vgrad,ems.employee_id,ems.workOne,ems.estartDate,ems.eendDate,ems.workTwo,ems.wstartDate,ems.wendDate,ems.workThree,ems.hstartDate,ems.hendDate FROM employee AS emp INNER JOIN education AS educ ON educ.employee_id='emp.id' INNER JOIN employment_history AS ems ON ems.employee_id='emp.id' INNER JOIN referrence AS ref ON ref.employee_id='emp.id' WHERE emp.id='$id'"); Is it okay to use INNER JOIN this way? Or should I modify my query to get the results that I wanted? I've also tried to use LEFT JOIN but still it doesn't return anything .I didn't know where did I go wrong. You see, as I have thought, I've been using the INNER JOIN in correct manner, (since it was placed before the WHILE CLAUSE). So I couldn't think of what could've possible went wrong. Do you guys have a suggestion? Thanks in advance.

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• JSP/Struts2/Hibernate: loop through a self-referencing table.

  - by TBW

  Hello everyone, Let's say we have a self-referencing table called PERSON, with the following columns: ID, PARENT, where PARENT is a foreign key to the ID column of another element in the PERSON table. Of course, many persons can have the same parent. I use Hibernate 3 in lazy fetching mode to deal with the database. Hibernate fetches a person element from the database, which is then put in the ValueStack by the Struts2 action, to be used on the result JSP page. Now the question is : In JSP, how can I do to display all the child (and the child's child, and so on, like a family tree) of this person element? Of course, for the n+1 children I can use the < s:iterator tag over the person.person. I can also nest another < s:iterator tag over person.person.person to get the n+2 children. But what if I want to do this in an automated manner, up to the last n+p child, displaying in the process all the children of all the n+1..n+p elements? I hope I have been clear enough. Thank you all for your time. -- TBW.

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• Codeigniter/mySQL question. Checking if several inserts are possible before actual insertion.

  - by Ethan

  Hey SO, So I'm trying to perform a couple inserts at once that are kind of co-dependent on each other. Let's say I'm doing a dog rating website. Anyone can add a dog to my database, but in doing so they also need to add a preliminary rating of the dog. Other people can then rate the dog afterwards. The dogs to ratings is a many to one relationship: a dog has many ratings. This means for my preliminary add, since I have the person both rate and add the dog, I need to take the rating, and set a foreign key to the dog's primary key. As far as I know, this means I have to actually add the dog, then check what that new addition's primary key is, and then put that in my rating before insertion. Now suppose something were to go wrong with the rating's insert, be it a string that's too long, or something that I've overlooked somehow. If the rating's failed, the dog has already been inserted, but the rating has not. In this case, I'd like the dog to not have been added in the first place. Does this mean I have to write code that says "if the rating fails, do a remove for the dog," or is there a way to predict what the key will be for the dog should everything go as planned. Is there a way to say "hold that spot," and then if everything works, add it? Any help would be greatly appreciated. Thanks!!

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• Adding Categories to my Articles in my Rails app (Small Help)

  - by user214038

  I'm currently building a semi-small ruby app for a project. The problem I'm currently facing is the following: I want to be Able to fit the Article into the Categories. I've already accomplish this by having two models. An article model with a foreign key of category_id and my Category model with the name of the category. With a has_one and belogs_to relationship. (We're assuming you can only fit an article into one category). Here's the piece of code. This is the new method, where i create a new article and load up all the categories. def new @article = Article.new @categories = Category.find(:all) end The problem comes when i try to get the category from a combo box in order to insert it along with the article. This is the combo box code : f.select(:category_id,@categories) And this is the create method: def create @category = Category.find(params[:id]) @article = @category.articles.new(params[:article]) if @article.save flash[:notice] = "Article Submitted Sucessfully" redirect_to user_path else render :action = 'new' end end I believe that the problem i have is in this line when i try to load up the selected category "@category = Category.find(params[:id])" because whenever i hardcode the this line into @category = Category.find(1) It Works perfectly

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• How can I go through a Set in JSP? (Hibernate Associations)

  - by Parris

  Hi All, So I am pretty new to JSP. I have tried this a few ways. Ways that would make sense in PHP or automagicy frameworks... I am probably thinking too much in fact... I have a hibernate one to many association. That is class x has many of class y. In class x's view.jsp. I would like to grab all of class y, where the foreign key of y matches the primary key of x and display them. It seems that hibernate properly puts this stuff into a set. Now, the question is how can I iterate through this set and then output it's contents... I am kind of stumped here. I tried to write a scriptlet, <% java.util.Iterator iter = aBean.getYs().iter(); // aBeans is the bean name // getYs would return the set and iter would return an iterator for the set while(iter.hasNext) { model.X a = new iter.next() %> <h1><%=a.getTitle()%></h1> <% } %> It would seem that that sort of thing should work? Hmmmmmm

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• How to map a 0..1 to 1 relationship in Entity Framework 3

  - by sako73

  I have two tables, Users, and Address. A the user table has a field that maps to the primary key of the address table. This field can be null. In plain english, Address exist independent of other objects. A user may be associated with one address. In the database, I have this set up as a foreign key relationship. I am attempting to map this relationship in the Entity Framework. I am getting errors on the following code: <Association Name="fk_UserAddress"> <End Role="User" Type="GenesisEntityModel.Store.User" Multiplicity="1"/> <End Role="Address" Type="GenesisEntityModel.Store.Address" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="Address"> <PropertyRef Name="addressId"/> </Principal> <Dependent Role="User"> <PropertyRef Name="addressId"/> </Dependent> </ReferentialConstraint> </Association> It is giving a "The Lower Bound of the multiplicity must be 0" error. I would appreciate it if anyone could explain the error, and the best way to solve it. Thanks for any help.

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• SQLAlchemy Custom Type Which Contains Multiple Columns

  - by Kekoa

  I would like to represent a datatype as a single column in my model, but really the data will be stored in multiple columns in the database. I cannot find any good resources on how to do this in SQLAlchemy. I would like my model to look like this(this is a simplified example using geometry instead of my real problem which is harder to explain): class 3DLine(DeclarativeBase): start_point = Column(my.custom.3DPoint) end_point = Column(my.custom.3DPoint) This way I could assign an object with the (x, y, z) components of the point at once without setting them individually. If I had to separate each component, this could get ugly, especially if each class has several of these composite objects. I would combine the values into one encoded field except that I need to query each value separately at times. I was able to find out how to make custom types using a single column in the documentation. But there's no indication that I can map a single type to multiple columns. I suppose I could accomplish this by using a separate table, and each column would be a foreign key, but in my case I don't think it makes sense to have a one to one mapping for each point to a separate table, and this still does not give the ability to set the related values all at once.

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• ZF2 - How to use the Hydrator/exchangeArray() to populate a nested object

  - by Dominic Watson

  I've got an object with values that are stored in my database. My object also contains another object which is stored in the database using just the ID of it (foreign key). http://framework.zend.com/manual/2.0/en/modules/zend.stdlib.hydrator.html Before the Hydrator/exchangeArray functionality in ZF2 you would use a Mapper to grab everything you need to create the object. Now I'm trying to eliminate this extra layer by just using Hydration/exchangeArray to populate my objects but am a bit stuck on creating the nested object. Should my entity have the Inner object's table injected into it so I can create it if the ID of it is passed to my 'exchangeArray' ? Here are example entities as an example. // Village id, name, position, square_id // Map Square id, name, type Upon sending square_id to my Village's exchangeArray() function. It would get the mapTable and use hydrator to pull in the square using the ID I have. It doesn't seem right to be to have mapper instances inside my entity as I thought they should be disconnected from anything but it's own entity specific parameters and functionality?

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• How to Map Two Tables To One Class in Fluent NHibernate

  - by Richard Nagle

  I am having a problem with fluent nhiberbate mapping two tables to one class. I have the following database schema: TABLE dbo.LocationName ( LocationId INT PRIMARY KEY, LanguageId INT PRIMARY KEY, Name VARCHAR(200) ) TABLE dbo.Language ( LanguageId INT PRIMARY KEY, Locale CHAR(5) ) And want to build the following class definition: public class LocationName { public virtual int LocationId { get; private set; } public virtual int LanguageId { get; private set; } public virtual string Name { get; set; } public virtual string Locale { get; set; } } Here is my mapping class: public LocalisedNameMap() { WithTable("LocationName"); UseCompositeId() .WithKeyProperty(x => x.LanguageId) .WithKeyProperty(x => x.LocationId); Map(x => x.Name); WithTable("Language", lang => { lang.WithKeyColumn("LanguageId"); lang.Map(x => x.Locale); }); } The problem is with the mapping of the Locale field being from another table, and in particular that the keys between those tables don't match. Whenever I run the application with this mapping I get the following error on startup: Foreign key (FK7FC009CCEEA10EEE:Language [LanguageId])) must have same number of columns as the referenced primary key (LocationName [LanguageId, LocationId]) How do I tell nHibernate to map from LocationName to Language using only the LanguageId field?

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• How can I use a compound condition in a join in Linq?

  - by Gary McGill

  Let's say I have a Customer table which has a PrimaryContactId field and a SecondaryContactId field. Both of these are foreign keys that reference the Contact table. For any given customer, either one or two contacts may be stored. In other words, PrimaryContactId can never be NULL, but SecondaryContactId can be NULL. If I drop my Customer and Contact tables onto the "Linq to SQL Classes" design surface, the class builder will spot the two FK relationships from the Customer table to the Contact table, and so the generated Customer class will have a Contact field and a Contact1 field (which I can rename to PrimaryContact and SecondaryContact to avoid confusion). Now suppose that I want to get details of all the contacts for a given set of customers. If there was always exactly one contact then I could write something like: from customer in customers join contact in contacts on customer.PrimaryContactId equals contact.id select ... ...which would be translated into something like: SELECT ... FROM Customer INNER JOIN Contact ON Customer.FirstSalesPersonId = Contact.id But, because I want to join on both the contact fields, I want the SQL to look something like: SELECT ... FROM Customer INNER JOIN Contact ON Customer.FirstSalesPersonId = Contact.id OR Customer.SecondSalesPersonId = Contact.id How can I write a Linq expression to do that?

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• ActiveRecord Validations for Models with has_many, belongs_to associations and STI

  - by keruilin

  I have four models: User Award Badge GameWeek The associations are as follows: User has many awards. Award belongs to user. Badge has many awards. Award belongs to badge. User has many game_weeks. GameWeek belongs to user. GameWeek has many awards. Award belongs to game_week. Thus, user_id, badge_id and game_week_id are foreign keys in awards table. Badge implements an STI model. Let's just say it has the following subclasses: BadgeA and BadgeB. Some rules to note: The game_week_id fk can be nil for BadgeA, but can't be nil for BadgeB. Here are my questions: For BadgeA, how do I write a validation that it can only be awarded one time? That is, the user can't have more than one -- ever. For BadgeB, how do I write a validation that it can only be awarded one time per game week?

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• Help dealing with data dependency between two registration forms

  - by franko75

  I have a tricky issue here with a registration of both a user and his/her pet. Both the user and the pet are treated as separate entities and both require separate registration forms. However, the user's pet has to be linked to the user via a foreign key in the database. The process is basically that when a new user joins the site, firstly they register their pet, then they register themselves. The reason for this order is to check their pet's eligibility for the site (there are some criteria to be met) first, instead of getting the user to sign up only to then find out their pet is ineligible. It is this ordering of the form submissions which is causing me a bit of a headache, as follows... The site is being developed with an MVC framework, and the User registration process is managed via a method in a User_form controller, while the pet registration process is managed via a method in the Pet_form controller. The pet registration form happens first, and the pet data can be saved without the owner_id at this stage, with the user id possibly being added (e.g by retrieving pet's id from session) following user registration. However, doing it this way could potentially result in redundant data, where pet records would be created in the database, but if the user doesn't actually register themselves too, then the pets will be ownerless records in the DB. Other option is to serialize the new pet's data at the pet registration stage, don't save it to the DB until the user fills out their registration form. Once the user is created, i can pass serialised data AND the owner_id to a method in the Pet Model which can update the DB. However, I also need to set the newly created $pet to $this-pet which I then access for a sequence of other related forms. Should I just set the session variable in the model method? Then in the Pet controller constructor, do a check for pet stored in session, if yes, assign to $this-pet... If this makes any sense to anybody and you have some advice, i'd be grateful to hear it!

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• Databinding expression for retrieving value of related collection using LINQ

  - by joshb

  I have a GridView that is bound to a LINQDataSource control that is returning a collection of customers. Within my DataGrid I need to display the home phone number of a customer, if they have one. The phone numbers of a customer are stored in a separate table with a foreign key pointing to the customer table. The following binding expression gets me the first phone number for a customer: <asp:TemplateField HeaderText="LastName" SortExpression="LastName"> <ItemTemplate> <asp:Label ID="PhoneLabel" runat="server" Text='<%# Eval("Phones[0].PhoneNumber") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> I need to figure out how to get the home phone number specifically (filter based on phone type) and handle the scenario where the customer does not have a home phone in the database. Right now it's throwing an out of range exception if the customer does not have any phone numbers. I've tried using the Where operator with a lambda expression to filter the phone type but it doesn't work: <%# Eval("Phones.Where(p => p.PhoneTypeId == 2).PhoneNumber") %> Solutions or links to any good articles on the subject would be much appreciated.

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• Ruby on Rails: How to create associated models on the fly ?

  - by Misha Moroshko

  I have the following models: class Product < ActiveRecord::Base belongs_to :brand belongs_to :model accepts_nested_attributes_for :brand, :model ... end class Brand < ActiveRecord::Base has_many :products has_many :models ... end class Model < ActiveRecord::Base has_many :products belongs_to :brand accepts_nested_attributes_for :brand ... end I have a problem to create a new product. Here is the relevant code in the controller: class ProductsController < ApplicationController ... def create @product = Product.new(params[:product]) if @product.save ... # Here is the error end ... end When user adds a new brand and a new model, params[:product] contains the following: "brand_attributes"=>{"name"=>"my_new_brand"} "model_attributes"=>{"model_no"=>"my_new_model"} and I got the following error: Mysql2::Error: Column 'brand_id' cannot be null: INSERT INTO `models` ... because model has a foreign key brand_id which is not set. I can't set it because the brand (like the model) is created on the fly when the product is created. I don't want to create the brand before the product, because then I the product has errors, I will need to delete the created brand. Then I tried to change params[:product] like this: "brand_attributes"=>{"name"=>"my_new_brand", "model_attributes"=>{"model_no"=>"my_new_model"}} but I end up with this: unknown attribute: model_attributes What would be the proper way to handle this ?

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• Do I need to write a trigger for such a simple constraint?

  - by Paul Hanbury

  I really had a hard time knowing what words to put into the title of my question, as I am not especially sure if there is a database pattern related to my problem. I will try to simplify matters as much as possible to get directly to the heart of the issue. Suppose I have some tables. The first one is a list of widget types: create table widget_types ( widget_type_id number(7,0) primary key, description varchar2(50) ); The next one contains icons: create table icons ( icon_id number(7,0) primary key, picture blob ); Even though the users get to select their preferred widget, there is a predefined subset of widgets that they can choose from for each widget type. create table icon_associations ( widget_type_id number(7,0) references widget_types, icon_id number(7,0) references icons, primary key (widget_type_id, icon_id) ); create table icon_prefs ( user_id number(7,0) references users, widget_type_id number(7,0), icon_id number(7,0), primary key (user_id, widget_type_id), foreign key (widget_type_id, icon_id) references icon_associations ); Pretty simple so far. Let us now assume that if we are displaying an icon to a user who has not set up his preferences, we choose one of the appropriate images associated with the current widget. I'd like to specify the preferred icon to display in such a case, and here's where I run into my problem: alter table icon_associations add ( is_preferred char(1) check( is_preferred in ('y','n') ) ) ; I do not see how I can enforce that for each widget_type there is one, and only one, row having is_preferred set to 'y'. I know that in MySQL, I am able to write a subquery in my check constraint to quickly resolve this issue. This is not possible with Oracle. Is my mistake that this column has no business being in the icon_associations table? If not where should it go? Is this a case where, in Oracle, the constraint can only be handled with a trigger? I ask only because I'd like to go the constraint route if at all possible. Thanks so much for your help, Paul

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• shreding xml column

  - by csetzkorn

  Hi, I have a XML column which contains XML like this: <Set> <Element> <ID> 1 </ID> <List> <ListElement> <Part1> ListElement 1 </Part1> </ListElement> <ListElement> <Part1> ListElement2 </Part1> </ListElement> </List> </Element> <Element> <ID> 2 </ID> <List> <ListElement> <Part1> ListElement3 </Part1> </ListElement> <ListElement> <Part1> ListElement4 </Part1> </ListElement> </List> </Element> </Set> I would like to shred this into a relation table containing this: ID, ListElement 1, ListElement1 1, ListElement2 2, ListElement3 2, ListElement4 I am able to obtain the content of the Parts using something like this: select List.value('(Part1/text())[1]', 'varchar(max)') as test from Table CROSS APPLY xml.nodes('// Element/List/ListElement') AS List(List) but I have not yet achieved to keep the ‘foreign key’ (the ID value). Thanks. Best wishes, Christian

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• Select rows from table1 and all the children from table2 into an object

  - by Patrick

  I want to pull data from table "Province_Notifiers" and also fetch all corresponding items from table "Province_Notifier_Datas". The table "Province_Notifier" has a guid to identify it (PK), table "Province_Notifier_Datas" has a column called BelongsToProvinceID witch is a foreign key to the "Province_Notifier" tables guid. I tried something like this: var records = from data in ctx.Province_Notifiers where DateTime.Now >= data.SendTime && data.Sent == false join data2 in ctx.Province_Notifier_Datas on data.Province_ID equals data2.BelongsToProvince_ID select new Province_Notifier { Email = data.Email, Province_ID = data.Province_ID, ProvinceName = data.ProvinceName, Sent = data.Sent, UserName = data.UserName, User_ID = data.User_ID, Province_Notifier_Datas = (new List<Province_Notifier_Data>().AddRange(data2)) }; This line is not working and i am trying to figure out how topull the data from table2 into that Province_Notifier_Datas variable. Province_Notifier_Datas = (new List<Province_Notifier_Data>().AddRange(data2)) I can add a record easily by adding the second table row into the Province_Notifier_Datas but i can't fetch it back. Province_Notifier dbNotifier = new Province_Notifier(); // set some values for dbNotifier dbNotifier.Province_Notifier_Datas.Add( new Province_Notifier_Data { BelongsToProvince_ID = userInput.Value.ProvinceId, EventText = GenerateNotificationDetail(notifierDetail) }); This works and inserts the data correctly into both tables. Edit: These error messages is thrown: Cannot convert from 'Province_Notifier_Data' to 'System.Collections.Generic.IEnumerable' If i look in Visual Studio, the variable "Province_Notifier_Datas" is of type System.Data.Linq.EntitySet The best overloaded method match for 'System.Collections.Generic.List.AddRange(System.Collections.Generic.IEnumerable)' has some invalid arguments Edit: var records = from data in ctx.Province_Notifiers where DateTime.Now >= data.SendTime && data.Sent == false join data2 in ctx.Province_Notifier_Datas on data.Province_ID equals data2.BelongsToProvince_ID into data2list select new Province_Notifier { Email = data.Email, Province_ID = data.Province_ID, ProvinceName = data.ProvinceName, Sent = data.Sent, UserName = data.UserName, User_ID = data.User_ID, Province_Notifier_Datas = new EntitySet<Province_Notifier_Data>().AddRange(data2List) }; Error 3 The name 'data2List' does not exist in the current context.

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• Avoiding repeated subqueries when 'WITH' is unavailable

  - by EloquentGeek

  MySQL v5.0.58. Tables, with foreign key constraints etc and other non-relevant details omitted for brevity: CREATE TABLE `fixture` ( `id` int(11) NOT NULL auto_increment, `competition_id` int(11) NOT NULL, `name` varchar(50) NOT NULL, `scheduled` datetime default NULL, `played` datetime default NULL, PRIMARY KEY (`id`) ); CREATE TABLE `result` ( `id` int(11) NOT NULL auto_increment, `fixture_id` int(11) NOT NULL, `team_id` int(11) NOT NULL, `score` int(11) NOT NULL, `place` int(11) NOT NULL, PRIMARY KEY (`id`) ); CREATE TABLE `team` ( `id` int(11) NOT NULL auto_increment, `name` varchar(50) NOT NULL, PRIMARY KEY (`id`) ); Where: A draw will set result.place to 0 result.place will otherwise contain an integer representing first place, second place, and so on The task is to return a string describing the most recently played result in a given competition for a given team. The format should be "def Team X,Team Y" if the given team was victorious, "lost to Team X" if the given team lost, and "drew with Team X" if there was a draw. And yes, in theory there could be more than two teams per fixture (though 1 v 1 will be the most common case). This works, but feels really inefficient: SELECT CONCAT( (SELECT CASE `result`.`place` WHEN 0 THEN "drew with" WHEN 1 THEN "def" ELSE "lost to" END FROM `result` WHERE `result`.`fixture_id` = (SELECT `fixture`.`id` FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` WHERE `fixture`.`competition_id` = 2 AND `result`.`team_id` = 1 ORDER BY `fixture`.`played` DESC LIMIT 1) AND `result`.`team_id` = 1), ' ', (SELECT GROUP_CONCAT(`team`.`name`) FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` LEFT JOIN `team` ON `result`.`team_id` = `team`.`id` WHERE `fixture`.`id` = (SELECT `fixture`.`id` FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` WHERE `fixture`.`competition_id` = 2 AND `result`.`team_id` = 1 ORDER BY `fixture`.`played` DESC LIMIT 1) AND `team`.`id` != 1) ) Have I missed something really obvious, or should I simply not try to do this in one query? Or does the current difficulty reflect a poor table design?

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• @ManyToMany Duplicate Entry Exception

  - by zp26

  I have mapped a bidirectional many-to-many exception between the entities Course and Trainee in the following manner: Course { ... private Collection<Trainee> students; ... @ManyToMany(targetEntity = lesson.domain.Trainee.class, cascade = {CascadeType.All}, fetch = {FetchType.EAGER}) @Jointable(name="COURSE_TRAINEE", joincolumns = @JoinColumn(name="COURSE_ID"), inverseJoinColumns = @JoinColumn(name = "TRAINEE_ID")) @CollectionOfElements public Collection<Trainee> getStudents() { return students; } ... } Trainee { ... private Collection<Course> authCourses; ... @ManyToMany(cascade = {CascadeType.All}, fetch = {FetchType.EAGER}, mappedBy = "students", targetEntity = lesson.domain.Course.class) @CollectionOfElements public Collection<Course> getAuthCourses() { return authCourses; } ... } Instead of creating a table where the Primary Key is made of the two foreign keys (imported from the table of the related two entities), the system generates the table "COURSE_TRAINEE" with the following schema: I am working on MySQL 5.1 and my App. Server is JBoss 5.1. Does anyone guess why?

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• Entity framework self referencing loop detected

  - by Lyd0n

  I have a strange error. I'm experimenting with a .NET 4.5 Web API, Entity Framework and MS SQL Server. I've already created the database and set up the correct primary and foreign keys and relationships. I've created a .edmx model and imported two tables: Employee and Department. A department can have many employees and this relationship exists. I created a new controller called EmployeeController using the scaffolding options to create an API controller with read/write actions using Entity Framework. In the wizard, selected Employee as the model and the correct entity for the data context. The method that is created looks like this: // GET api/Employee public IEnumerable<Employee> GetEmployees() { var employees = db.Employees.Include(e => e.Department); return employees.AsEnumerable(); } When I call my API via /api/Employee, I get this error: ...The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; ...System.InvalidOperationException","StackTrace":null,"InnerException":{"Message":"An error has occurred.","ExceptionMessage":"Self referencing loop detected with type 'System.Data.Entity.DynamicProxies.Employee_5D80AD978BC68A1D8BD675852F94E8B550F4CB150ADB8649E8998B7F95422552'. Path '[0].Department.Employees'.","ExceptionType":"Newtonsoft.Json.JsonSerializationException","StackTrace":" ... Why is it self referencing [0].Department.Employees? That doesn't make a whole lot of sense. I would expect this to happen if I had circular referencing in my database but this is a very simple example. What could be going wrong?

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• How to use Transaction in Entity FrameWork?

  - by programmerist

  How to use Transaction in Entity FrameWork? i read some links on Stackoverflow : http://stackoverflow.com/questions/815586/entity-framework-using-transactions-or-savechangesfalse-and-acceptallchanges BUT; i have 3 table so i have 3 entities: CREATE TABLE Personel (PersonelID integer PRIMARY KEY identity not null, Ad varchar(30), Soyad varchar(30), Meslek varchar(100), DogumTarihi datetime, DogumYeri nvarchar(100), PirimToplami float); Go create TABLE Prim (PrimID integer PRIMARY KEY identity not null, PersonelID integer Foreign KEY references Personel(PersonelID), SatisTutari int, Prim float, SatisTarihi Datetime); Go CREATE TABLE Finans (ID integer PRIMARY KEY identity not null, Tutar float); Personel, Prim,Finans my tables. if you look Prim table you can see Prim value float value if i write a textbox not float value my transaction must run. using (TestEntities testCtx = new TestEntities()) { using (TransactionScope scope = new TransactionScope()) { // do someyihng... testCtx.Personel.SaveChanges(); // do someyihng... testCtx.Prim.SaveChanges(); // do someyihng... testCtx.Finans.SaveChanges(); scope .Complete(); success = true; } } How can i do that?

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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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• mailing system DB structure, need help

  - by Anna

  i have a system there user(sender) can write a note to friends(receivers), number of receivers=0. Text of the message is saved in DB and visible to sender and all receivers then they login to system. Sender can add more receivers at any time. More over any of receivers can edit the message and even remove it from DB. For this system i created 3 tables, shortly: users(userID, username, password) messages(messageID, text) list(id, senderID, receiverID, messageID) in table "list" each row corresponds to pair sender-receiver, like sender_x_ID -- receiver_1_ID -- message_1_ID sender_x_ID -- receiver_2_ID -- message_1_ID sender_x_ID -- receiver_3_ID -- message_1_ID Now the problem is: 1. if user deletes the message from table "messages" how to automatically delete all rows from table "list" which correspond to deleted message. Do i have to include some foreign keys? More important: 2. if sender has let say 3 receivers for his message1 (username1, username2 and username3) and at certain moment decides to add username4 and username5 and at the same time exclude username1 from the list of receivers. PHP code will get the new list of receivers (username2, username3, username4, username5) That means insert to table "list" sender_x_ID -- receiver_4_ID -- message_1_ID sender_x_ID -- receiver_5_ID -- message_1_ID and also delete from table "list" the row corresponding to user1 (which is not in the list or receivers any more) sender_x_ID -- receiver_1_ID -- message_1_ID which sql query to send from PHP to make it in an easy and intelligent way? Please help! Examples of sql queries would be perfect!

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• iPhone - Using sql database - insert statement failing

  - by Satyam svv

  Hi, I'm using sqlite database in my iphone app. I've a table which has 3 integer columns. I'm using following code to write to that database table. -(BOOL)insertTestResult { NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString* documentsDirectory = [paths objectAtIndex:0]; NSString* dataBasePath = [documentsDirectory stringByAppendingPathComponent:@"test21.sqlite3"]; BOOL success = NO; sqlite3* database = 0; if(sqlite3_open([dataBasePath UTF8String], &database) == SQLITE_OK) { BOOL res = (insertResultStatement == nil) ? createStatement(insertResult, &insertResultStatement, database) : YES; if(res) { int i = 1; sqlite3_bind_int(insertResultStatement, 0, i); sqlite3_bind_int(insertResultStatement, 1, i); sqlite3_bind_int(insertResultStatement, 2, i); int err = sqlite3_step(insertResultStatement); if(SQLITE_ERROR == err) { NSAssert1(0, @"Error while inserting Result. '%s'", sqlite3_errmsg(database)); success = NO; } else { success = YES; } sqlite3_finalize(insertResultStatement); insertResultStatement = nil; } } sqlite3_close(database); return success;} The command sqlite3_step is always giving err as 19. I'm not able to understand where's the issue. Tables are created using following queries: CREATE TABLE [Patient] (PID integer NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,PFirstName text NOT NULL,PLastName text,PSex text NOT NULL,PDOB text NOT NULL,PEducation text NOT NULL,PHandedness text,PType text) CREATE TABLE PatientResult(PID INTEGER,PFreeScore INTEGER NOT NULL,PForcedScore INTEGER NOT NULL,FOREIGN KEY (PID) REFERENCES Patient(PID)) I've only one entry in Patient table with PID = 1 BOOL createStatement(const char* query, sqlite3_stmt** stmt, sqlite3* database){ BOOL res = (sqlite3_prepare_v2(database, query, -1, stmt, NULL) == SQLITE_OK); if(!res) NSLog( @"Error while creating %s => '%s'", query, sqlite3_errmsg(database)); return res;}

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