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• Database relationships using phpmyAdmin (composite keys)

  - by Cool Hand Luke UK

  Hi, I hope this question is not me being dense. I am using phpmyAdmin to create a database. I have the following four tables. Don't worry about that fact place and price are optional they just are. Person (Mandatory) Item (Mandatory) Place (Optional) Price (Optional) Item is the main table. It will always have person linked. * I know you do joins in mysql for the tables. If I want to link the tables together I could use composite keys (using the ids from each table), however is this the most correct way to link the tables? It also means item will have 5 ids including its own. This all cause null values (apparently a big no no, which I can understand) because if place and price are optional and are not used on one entry to the items table I will have a null value there. Please help! Thanks in advance. I hope this makes sense.

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• Establishing persistent connection to a database in Java

  - by gmile

  I've ran through several examples over the web, and found that every single time I need something from the DB, I should write the following code: try { // Step 1: Load the JDBC driver. Class.forName("mysql_driver_name"); // Step 2: Establish the connection to the database. String url = "jdbc:string_to_mysql_server"; Connection conn = DriverManager.getConnection(url,"user1","password"); // fetch from the DB ... } catch (Exception e) { System.err.println("Got an exception! "); System.err.println(e.getMessage()); } It's very annoying to put up this code every time I want something from the DB, so the question is - is there a way to only once connect entirely all my app to the DB somehow at the very start point, avoiding copy-pasting mentioned code, and then be able to do everything I want with DB? I've quickly looked through NetBeans's Project menu, but didn't find any clue on how to configurate a persistent connection to a selected DB. If it's important, i'm writing a purely desktop app, i.e. using Java EE. Also, it's worth mentioning that I'm a kinda beginner in Java.

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• Java login form with database connection

  - by Muhammed Yoosuf

  I am creating a login form in java by having a database connection, and I need 2 open DIFFERENT forms for each user. However, all of the three forms open except for one. The forms I have are, MAinWindow Nursery Primary Secondary ALL THE FORMS OPEN except for the nursery form, when I enter the correct username it displays the Primary form. ANY HELP SOON char[] DBUserArray; DBUserArray=name.toCharArray(); char [] DBPassArray; DBPassArray=pass.toCharArray(); char AdminArray []=AdminUser.toCharArray(); char NurArray []=NurHead.toCharArray(); char[] PriArray =PriHead.toCharArray(); char[] SecArray=SecHead.toCharArray(); char[] input = txtpassword.getPassword(); String user=txtusername.getText(); char [] userString; userString=user.toCharArray(); if(userString.length!=DBUserArray.length && input.length!=DBPassArray.length) { JOptionPane.showMessageDialog(null, "Username and Password Wrong","User Login",JOptionPane.ERROR_MESSAGE); } else { if(userString.length!=AdminArray.length) { if(userString.length!=PriArray.length) { if(userString.length!=NurArray.length) { if(userString.length!=SecArray.length) { } else { new Secondary().setVisible(true); setVisible(false); } } else { new Nursery().setVisible(true); setVisible(false); } } else { new Primary().setVisible(true); setVisible(false); } } else { new MainWindow().setVisible(true); setVisible(false); } }

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• Hierarchical/Nested Database Structure for Comments

  - by Stephen Melrose

  Hi, I'm trying to figure out the best approach for a database schema for comments. The problem I'm having is that the comments system will need to allow nested/hierarchical comments, and I'm not sure how to design this out properly. My requirements are, Comments can be made on comments, so I need to store the tree hierarchy I need to be able to query the comments in the tree hierarchy order, but efficiently, preferably in a fast single query, but I don't know if this is possible I'd need to make some wierd queries, e.g. pull out the latest 5 root comments, and a maximum of 3 children for each one of those I read an article on the MySQL website on this very subject, http://dev.mysql.com/tech-resources/articles/hierarchical-data.html The "Nested Set Model" in theory sounds like it will do what I need, except I'm worried about querying the thing, and also inserting. If this is the right approach, How would I do my 3rd requirement above? If I have 2000 comments, and I add a new sub-comment on the first comment, that will be a LOT of updating to do. This doesn't seem right to me? Or is there a better approach for the type of data I'm wanting to store and query? Thank you

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• Django Database design -- Is this a good stragety for overriding defaults

  - by rh0dium

  Hi SO's I have a question on good database design practices and I would like to leverage you guys for pointers. The project started out simple. Hey we have a bunch of questions we want answered for every project (no problem) Which turned into... Hey we have so many questions can we group them into sections (yup we can do that) Which lead into.. Can we weight these questions and I don't really want some of these questions for my project (Yes but we are getting difficult) And then I'm thinking they will want to have each section have it's own weight.. Requirements So there's the requirements - For n number of project Allow a admin member the ability select the questions for a project Allow the admin member to re-weigh or use the default weights for the questions Allow the admin member to re-weight the sections Allow team members to answer the questions. So here is what I came up with. Please feel free to comment and provide better examples models.py from django.db import models from django.contrib.sites.models import Site from django.conf import settings class Section(models.Model): """ This describes the various sections for a checklist: """ name = models.CharField(max_length=64) description = models.TextField() class Question(models.Model): """ This simply provides a simple way to list out the questions. """ question = models.CharField(max_length=255) answer_type = models.CharField(max_length=16) description = models.TextField() section = models.ForeignKey(Section) class ProjectQuestion(models.Model): """ These are the questions relevant to the project """ question = models.ForeignKey(Question) answer = models.CharField(max_length=255) required = models.BooleanField(default=True) weight = models.FloatField(default = XXX) class Project(models.Model): """ Here is where we want to gather our questions """ questions = models.ManyToManyField(ProjectQuestion) Immediate questions: - When I start a project - any ideas on how to "pre-populate" the questions (and ultimately the weights) for the project? - Is there a generally accepted method for doing this process that I am missing? Basically the idea that you refer to the questions overide your own default weight, and store the answer? - It appears that a good chuck of the work will be done in the views and that a lot of checking will need to occur there? Is that OK? Again - feel free to give me better strategies!! Thanks

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• Simple Database normalization question...

  - by user365531

  Hi all, I have a quick question regarding a database that I am designing and making sure it is normalized... I have a customer table, with a primary key of customerId. It has a StatusCode column that has a code which reflects the customers account status ie. 1 = Open, 2 = Closed, 3 = Suspended etc... Now I would like to have another field in the customer table that flags whether the account is allowed to be suspended or not... certain customers will be automatically suspended if they break there trading terms... others not... so the relevant table fields will be as so: Customers (CustomerId(PK):StatusCode:IsSuspensionAllowed) Now both fields are dependent on the primary key as you can not determine the status or whether suspensions are allowed on a particular customer unless you know the specific customer, except of course when the IsSuspensionAllowed field is set to YES, the the customer should never have a StatusCode of 3 (Suspended). It seems from the above table design it is possible for this to happen unless a check contraint is added to my table. I can't see how another table could be added to the relational design to enforce this though as it's only in the case where IsSuspensionAllowed is set to YES and StatusCode is set to 3 when the two have a dependence on each other. So after my long winded explanation my question is this: Is this a normalization problem and I'm not seeing a relational design that will enforce this... or is it actually just a business rule that should be enforced with a check contraint and the table is in fact still normalized. Cheers, Steve

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• how to get Contact database schema.

  - by kamiomar

  Dear, is there any link that provide me the Contact Schema. when i store new phone number in mobile, the informaion store in the database. so i need schema to create my own table for back purpose. i have alreay get People table column by the follwoing code. boolean displayFlag = false; String str = ""; Uri CONTACT_URI = People.CONTENT_URI; Cursor cursor = mContext.getContentResolver().query(CONTACT_URI, null, null, null, null); String columnNames = ""; if (cursor != null) { try { cursor.getCount(); if (cursor.moveToFirst()) { String[] columns = cursor.getColumnNames(); for (int i = 0; i < columns.length; i++) { columnNames += "colName" + cursor.getColumnName(i) + " : " + cursor.getString(i) + "colValue"; } } } finally { cursor.close(); } } createImage(columnNames); if (displayFlag) { Toast.makeText(mContext, str, Toast.LENGTH_SHORT).show(); } } Thanks

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• Database design MySQL using foreign keys

  - by dscher

  I'm having some a little trouble understanding how to handle the database end of a program I'm making. I'm using an ORM in Kohana, but am hoping that a generalized understanding of how to solve this issue will lead me to an answer with the ORM. I'm writing a program for users to manage their stock research information. My tables are basically like so: CREATE TABLE tags( id INT AUTO_INCREMENT NOT NULL PRIMARY KEY, tags VARCHAR(30), UNIQUE(tags) ) ENGINE=INNODB DEFAULT CHARSET=utf8; CREATE TABLE stock_tags( id INT AUTO_INCREMENT NOT NULL PRIMARY KEY, tag_id INT NOT NULL, stock_id INT NOT NULL, FOREIGN KEY (tag_id) REFERENCES tags(id), FOREIGN KEY(stock_id) REFERENCES stocks(id) ON DELETE CASCADE ) ENGINE=INNODB DEFAULT CHARSET=utf8; CREATE TABLE notes( id INT AUTO_INCREMENT NOT NULL, stock_id INT NOT NULL, notes TEXT NOT NULL, FOREIGN KEY (stock_id) REFERENCES stocks(id) ON DELETE CASCADE, PRIMARY KEY(id) ) ENGINE=INNODB DEFAULT CHARSET=utf8; CREATE TABLE links( id INT AUTO_INCREMENT NOT NULL, stock_id INT NOT NULL, links VARCHAR(2083) NOT NULL, FOREIGN KEY (stock_id) REFERENCES stocks(id) ON DELETE CASCADE, PRIMARY KEY(id) ) ENGINE=INNODB DEFAULT CHARSET=utf8; How would I get all the attributes of a single stock, including its links, notes, and tags? Do I have to add links, notes, and tags columns to the stocks table and then how do you call it? I know this differs using an ORM and I'd assume that I can use join tables in SQL. Thanks for any help, this will really help me understand the issue a lot better.

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• How do I query SQLite Database in Android?

  - by kunjaan

  I successfully created the Database and inserted a row however I cannot Query it for some reason. My Droid crashes everytime. String DATABASE_NAME = "myDatabase.db"; String DATABASE_TABLE = "mainTable"; String DATABASE_CREATE = "create table if not exists " + DATABASE_TABLE + " ( value VARCHAR not null);"; SQLiteDatabase myDatabase = null; myDatabase = openOrCreateDatabase(DATABASE_NAME, Context.MODE_PRIVATE, null); myDatabase.execSQL(DATABASE_CREATE); // Create a new row of values to insert. ContentValues newValues = new ContentValues(); // Assign values for each row. newValues.put("value", "kunjan"); // Insert the row into your table myDatabase.insert(DATABASE_TABLE, null, newValues); String[] result_columns = new String[] { "value" }; Cursor allRows = myDatabase.query(true, DATABASE_TABLE, result_columns, null, null, null, null, null, null); if (allRows.moveToFirst()) { String value = allRows.getString(1); TextView foo = (TextView) findViewById(R.id.TextView01); foo.setText(value); } allRows.close(); myDatabase.close();

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• Database localization

  - by Don

  Hi, I have a number of database tables that contain name and description columns which need to be localized. My initial attempt at designing a DB schema that would support this was something like: product ------- id name description local_product ------- id product_id local_name local_description locale_id locale ------ id locale However, this solution requires a new local_ table for every table that contains name and description columns that require localization. In an attempt to avoid this overhead I redesigned the schema so that only a single localization table is needed product ------- id localization_id localization ------- id local_name local_description locale_id locale ------ id locale Here's an example of the data which would be stored in this schema when there are 2 tables (product and country) requiring localization: country id, localization_id ----------------------- 1, 5 product id, localization_id ----------------------- 1, 2 localization id, local_name, local_description, locale_id ------------------------------------------------------ 2, apple, a delicious fruit, 2 2, pomme, un fruit délicieux, 3 2, apfel, ein köstliches Obst, 4 5, ireland, a small country, 2 5, irlande, un petite pay, 3 locale id, locale -------------- 2, en 3, fr 4, de Notice that the compound primary key of the localization table is (id, locale_id), but the foreign key in the product table only refers to the first element of this compound PK. This seems like 'a bad thing' from the POV of normalization. Is there any way I can fix this problem, or alternatively, is there a completely different schema that supports localization without creating a separate table for each localizable table? Update: A number of respondents have proposed a solution that requires creating a separate table for each localizable table. However, this is precisely what I'm trying to avoid. The schema I've proposed above almost solves the problem to my satisfaction, but I'm unhappy about the fact that the localization_id foreign keys only refer to part of the corresponding primary key in the localization table. Thanks, Don

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• Synchronizing one or more databases with a master database - Foreign keys

  - by Ikke

  I'm using Google Gears to be able to use an application offline (I know Gears is deprecated). The problem I am facing is the synchronization with the database on the server. The specific problem is the primary keys or more exactly, the foreign keys. When sending the information to the server, I could easily ignore the primary keys, and generate new ones. But then how would I know what the relations are. I had one sollution in mind, bet the I would need to save all the pk for every client. What is the best way to synchronize multiple client with one server db. Edit: I've been thinking about it, and I guess seqential primary keys are not the best solution, but what other possibilities are there? Time based doesn't seem right because of collisions which could happen. A GUID comes to mind, is that an option? It looks like generating a GUID in javascript is not that easy. I can do something with natural keys or composite keys. As I'm thinking about it, that looks like the best solution. Can I expect any problems with that?

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• Why doesn't access database update?

  - by Ryan

  Recently I met a strange problem, see code snips as below: var sqlCommand: string; connection: TADOConnection; qry: TADOQuery; begin connection := TADOConnection.Create(nil); try connection.ConnectionString := 'Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Test.MDB;Persist Security Info=False'; connection.Open(); qry := TADOQuery.Create(nil); try qry.Connection := connection; qry.SQL.Text := 'Select * from aaa'; qry.Open; qry.Append; qry.FieldByName('TestField1').AsString := 'test'; qry.Post; beep; finally qry.Free; end; finally connection.Free; end; end; First, Create a new access database named test.mdb and put it under the directory of this test project, we can create a new table named aaa in it which has only one text type field named TestField1. We set a breakpoint at line of "beep", then lunch the test application under ide debug mode, when ide stops at the breakpoint line (qry.post has been executed), at this time we use microsoft access to open test.mdb and open table aaa you will find there are no any changes in table aaa, if you let the ide continue running after pressing f9 you can find a new record is inserted in to table aaa, but if you press ctrl+f2 to terminate the application at the breakpoint, you will find the table aaa has no record been inserted, but in normal circumstance, a new record should be inserted in to the table aaa after qry.post executed. who can explain this problem , it troubles me so long time. thanks !!! BTW, the ide is delphi 2010, and the access mdb file is created by microsoft access 2007 under windows 7

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• Database layout for an application with geocoding features using geokit

  - by vooD

  I'm developing a real estate web catalogue and want to geocode every ad using geokit gem. My question is what would be the best database layout from the performance point if i want to make search by country, city of the selected country, administrative area or nearest metro station of the selected city. Available countries, cities, administrative areas and metro sations should be defined by the administrator of catalogue and must be validated by geocoding. I came up with single table: create_table "geo_locations", :force => true do |t| t.integer "geo_location_id" #parent geo location (ex. country is parent geo location of city t.string "country", :null => false #necessary for any geo location t.string "city", #not null for city geo location and it's children t.string "administrative_area" #not null for administrative_area geo location and it's children t.string "thoroughfare_name" #not null for metro station or street name geo location and it's children t.string "premise_number" #house number t.float "lng", :null => false t.float "lat", :null => false t.float "bound_sw_lat", :null => false t.float "bound_sw_lng", :null => false t.float "bound_ne_lat", :null => false t.float "bound_ne_lng", :null => false t.integer "mappable_id" t.string "mappable_type" t.string "type" #country, city, administrative area, metro station or address end Final geo location is address it contains all neccessary information to put marker of the real estate ad on the map. But i'm still stuck on search functionality. Any help would be highly appreciated.

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• best database design for city zip & state tables

  - by ryan a

  My application will need to reference addresses. Street info will be stored with my main objects but the rest needs to be stored seperately to reduce redundancy. How should I store/retrieve ZIPs, cities and states? Here are some of my ideas. single table solution (cant do relationships) [locations] locationID locationParent (FK for locationID - 0 for state entries) locationName (city, state) locationZIP two tables (with relationships, FK constraints, ref integrity) [state] stateID stateName [city] cityID stateID (FK for state.stateID) cityName zipCode three tables [state] stateID stateName [city] cityID stateID (FK for state.stateID) cityName [zip] zipID cityID (FK for city.cityID) zipName Then I read into ZIP codes amd how they are assigned. They aren't specifically related to cities. Some cities have more than one ZIP (ok will still work) but some ZIPs are in more than one city (oh snap) and some other ZIPs (very few) are in more than one state! Also some ZIPs are not even in the same state as the address they belong to at all. Seems ZIPs are made for carrier route identification and some remote places are best served by post offices in neighboring cities or states. Does anybody know of a good (not perfect) solution that takes this into consideration to minimize discrepencies as the database grows?

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• How to update a row in Android database

  - by Sajan

  Hi all I want to update a row on clicking on update button,but its doesn't work. I have used following code. public void btnUpdate(View v) { handeler.updateData(updateName.getText().toString(), updatePhone .getText().toString(), updateEmail.getText().toString(),id); } public void updateData(String name, String phone, String email, String id) { ContentValues values = new ContentValues(); values.put(COLUMN_FIRST, name); values.put(COLUMN_SECOND, phone); values.put(COLUMN_THIRD, email); database.update(TABLE_NAME, values, id, null); } public void search() { Cursor cursor = handeler.getData(); if (cursor.moveToFirst()) { String phoneNo; phoneNo = updateByPhone.getText().toString(); do { String s1 = cursor.getString(2); if (phoneNo.compareTo(s1) == 0) { id = cursor.getString(0); updateName.setText(cursor.getString(1)); updateEmail.setText(cursor.getString(3)); updatePhone.setText(cursor.getString(2)); } } while (cursor.moveToNext()); } } So if any know please suggest me how to solve it. Thanks

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• Java program will read from database, but not write to it

  - by ck1221

  I have a Java program that successfully connects to a mysql database that is hosted on godaddy's server. I can read from that db with out issue, however, when I try to write to it with INSERT or UPDATE for example, the query does not execute. I am using the 'admin' account that I set up through godaddy, I realize this is not the root account. I have checked and verified that the connection is not read only, and have logged out of phpmyadmin while the query ran. I'm not sure what else I can try or if anyone has experienced this issue. Maybe a setting to the connection I have failed to set? Or maybe its not possible since the db is hosted on godaddy's servers? Any help is great! Thanks. Here is some relevant code: Connection to db: Connection con; public DBconnection(String url, String user, String pass) { try { Class.forName("com.mysql.jdbc.Driver").newInstance(); con = DriverManager.getConnection (url,user,pass); if(!con.isClosed()) System.out.println("connecton open"); } catch (InstantiationException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();} } Send Query: public ResultSet executeQuery(String query) { ResultSet rs = null; try { Statement stmt = (Statement) con.createStatement(); rs = stmt.executeQuery(query); //while(rs.next()) //System.out.println(rs.getString("ticket_num")); } catch (SQLException e) {} return rs; } Insert Query (works in phpmyadmin): conn.executeQuery("INSERT INTO tickets VALUES(55555,'12/01/2012','me','reports','test','','','0','Nope')");

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• zend form check record no exists in database

  - by Yafa Su

  I have a form that check if email exists in the database within 2 tables. I'm using Zend_Validate_Db_NoRecordExists for both validate, but it only check the second one. Any idea why it's not working? class Application_Form_ReferUser extends Zend_Form { public $email, $freeDownload, $buyNow; public function init() { $this->setName('referUser'); $EmailExists = new Zend_Validate_Db_NoRecordExists( array( 'table' => 'referrals', 'field' => 'email' ) ); $EmailExists2 = new Zend_Validate_Db_NoRecordExists( array( 'table' => 'users', 'field' => 'email' ) ); $EmailExists->setMessage('This e-mail is already taken'); $EmailExists2->setMessage('This e-mail is already taken'); $this->email = $this->createElement('text', 'email') ->setLabel('Email') ->addValidator($EmailExists) ->addValidator($EmailExists2) ->addValidator('EmailAddress') ->setRequired(true); $this->freeDownload = $this->createElement('button', 'btn_free_download') ->setLabel('Free Download') ->setAttrib('type', 'submit'); $this->buyNow = $this->createElement('button', 'btn_buy_now') ->setLabel('Buy Now') ->setAttrib('type', 'submit'); $this->addElements(array($this->email, $this->freeDownload, $this->buyNow)); $elementDecorators = array( 'ViewHelper' ); $this->setElementDecorators($elementDecorators); } }

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• Database (MySQL) structuring: pros and cons of multiple tables

  - by Gideon

  I am collecting data and storing it MySQL, for: 75 variables 55 countries Each year I have, at this stage since I am building this tool created a single table, of variables / countries (storing 1 year worth of data). Next year (and for several years after that) a new set of data will be input for each country. There are therefore 3 variables in controlling data returned to a user reviewing all collected data. The general form of any query would be: Show me these specifics variables, for these specific countries, for these specific years. (Show me average age and weight, for USA and Canada, for 2012 and 2009, for example) My question is, it seems that I have two options for arranging this data: -Multiple tables where I create a table of country / variable for each year data is collected - Single table and simply add a column (field) for the year that data relates to. As far as I can tell I could make these database calls with either sructure, but is one more powerful / efficient / quicker, and why? Thanks for your consideration. It's a PDO / PHP interface if that is relevent.

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• Multilangual website using ASP and a database

  - by Noam Smadja

  i want to consult about something i do. my website has 3 languages. Hebrew (main), english and russian. i am using a database having a table with the fields: ID, fieldName, 1, 2, 3. where 1 2 3 are the languages. upon entering the website language 1 (hebrew) is chosen automaticly until you choose another. and saved as a session("currentLanguage"). i wrote a function langstirng whice recieves a field name and prints the value acording to the language in session("currentLanguage"): Dim languageStrings Set languageStrings = Server.CreateObject("ADODB.Recordset") languageStrings.ActiveConnection = MM_KerenDB_STRING languageStrings.Source = "SELECT fieldName,"&current_Language&"FROM Multilangual" languageStrings.CursorType = 0 languageStrings.CursorLocation = 2 languageStrings.LockType = 1 languageStrings.Open() sub langstring(fieldName) do while NOT(languageStrings.EOF) if (languageStrings.fields.item("fieldName").value = fieldName) then exit do else languageStrings.movenext end if loop if (languageStrings.EOF) then response.Write("***"&fieldName&"***") else response.Write(languageStrings.fields.item(currentLanguage+1).value) end if languageStrings.movefirst end sub and i use it like so: <div>langstring("header")</div>. i find it stupid that i keep sending the query to the server on any and every page. since the multilangual table does not change "THAT" often i want to somehow save the recordset for the current browsing. I am looking help for THIS solution, Please.

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• Zip multiple database PDF blob files

  - by Michael

  I have a database table that contains numerous PDF blob files. I am attempting to combine all of the files into a single ZIP file that I can download and then print. Please help! <?php include '../config.php'; include '../connect.php'; $session = $_GET['session']; $query = "SELECT $tbl_uploads.username, $tbl_uploads.description, $tbl_uploads.type, $tbl_uploads.size, $tbl_uploads.content, $tbl_members.session FROM $tbl_uploads LEFT JOIN $tbl_members ON $tbl_uploads.username = $tbl_members.username WHERE $tbl_members.session = '$session'"; $result = mysql_query($query) or die('Error, query failed'); $files = array(); while(list($username, $description, $type, $size, $content) = mysql_fetch_array($result)) { $files[] = "$username-$description.pdf"; } $zip = new ZipArchive; $zip->open('file.zip', ZipArchive::CREATE); foreach ($files as $file) { $zip->addFile($file); } $zip->close(); header('Content-Type: application/zip'); header('Content-disposition: attachment; filename=filename.zip'); header('Content-Length: ' . filesize($zipfilename)); readfile($zipname); exit(); ?>

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• Saving Data to Relational Database (Entity Framework)

  - by sheefy

  I'm having a little bit of trouble saving data to a database. Basically, I have a main table that has associations to other tables (Example Below). Tbl_Listing ID UserID - Associated to ID in User Table CategoryID - Associated to ID in Category Table LevelID - Associated to ID in Level Table. Name Address Normally, it's easy for me to add data to the DB (using Entity Framework). However, I'm not sure how to add data to the fields with associations. The numerous ID fields just need to hold an int value that corresponds with the ID in the associated table. For example; when I try to access the column in the following manner I get a "Object reference not set to an instance of an object." error. Listing NewListing = new Listing(); NewListing.Tbl_User.ID = 1; NewListing.Tbl_Category.ID = 2; ... DBEntities.AddToListingSet(NewListing); DBEntities.SaveChanges(); I am using NewListing.Tbl_User.ID instead of NewListing.UserID because the UserID field is not available through intellisense. If I try and create an object for each related field I get a "The relationship between the two objects cannot be defined because they are attached to different ObjectContext objects." error. With this method, I am trying to add the object without the .ID shown above - example NewListing.User = UserObject. I know this should be simple as I just want to reference the ID from the associated table in the main Listing's table. Any help would be greatly appreciated. Thanks in advance, -S

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• java class that simulates a simple database table

  - by ericso

  I have a collection of heterogenous data that I pull from a database table mtable. Then, for every unique value uv in column A, I compute a function of (SELECT * FROM mtable WHERE A=uv). Then I do the same for column B, and column C. There are rather a lot of unique values, so I don't want to hit the db repeatedly - I would rather have a class that replicates some of the functionality (most importantly some version of SELECT WHERE). Additionally, I would like to abstract the column names away from the class definition, if that makes any sense - the constructor should take a list of names as a parameter, and also, I suppose, a list of types (right now this is just a String[], which seems hacky). I'm getting the initial data from a RowSet. I've more or less done this by using a hashmap that maps Strings to lists/arrays of Objects, but I keep getting bogged down in comparisons and types, and am thinking that my current implementation really isn't as clean and clear as it could be. I'm pretty new to java, also, and am not sure if I'm not going down a completely incorrect path. Does anyone have any suggestions?

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• Displaying a message after adding duplicate records in database

  - by user1770370

  I wrote program in C# winforms and SQL server and LINQ to SQL. I use user control instead of form. In my user control, I put 3 textbox, txtStartNumber, txtEndNumber, txtQuantity. user define value of textboxes, when clicked button, it will insert some records according to the value of txtQuantity. I want to when duplicate number is created, it won't add to database and display message. how do i do? I must write code in code behind or server side? i must set this in store procedure or trigger? private void btnSave_Click(object sender, EventArgs e) { long from = Convert.ToInt64(txt_barcode_f.Text); long to = Convert.ToInt64(txt_barcode_t.Text); long quantity = Convert.ToInt64(to - from); int card_Type_ID=Convert.ToInt32(cmb_BracodeType .SelectedValue); long[] arrCardNum = new long[(to - from)]; arrCardNum[0]=from; for (long i = from; i < to; i++) { for(int j=0; j<(to-from) ;j++) { arrCardNum[j]=from+j; string r = arrCardNum[j].ToString(); sp.SaveCards(r, 2, card_Type_ID, SaveDate, 2); } } } Stored Procedure code. ALTER PROCEDURE dbo.SaveCards @Barcode_Num int ,@Card_Status_ID int ,@Card_Type_ID int ,@SaveDate varchar(10) ,@Save_User_ID int AS BEGIN INSERT INTO [Parking].[dbo].[TBL_Cards] ([Barcode_Num] ,[Card_Status_ID] ,[Card_Type_ID] ,[Save_User_ID]) VALUES (@Barcode_Num ,@Card_Status_ID ,@Card_Type_ID ,@Save_User_ID) END

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• Database tables with dynamic information

  - by Tim Fennis

  I've googled this and found that it's almost impossible to create a database with dynamic collumns. I'll explain my problem first. I am making a webshop for a customer. It has multiple computer products for sale. CPU's HDD's RAM ect. All these products have different properties, a CPU has an FSB, RAM has a CAS latency. But this is very inconvenient because my orders table needs foreign keys to different tables which is impossible. An other option is to store all the product specific information in a varchar or blob field and let PHP figure it out. The problem with this solution is that the website needs a PC builder. A step-by-step guide to building your PC. So for instance if a customer decides he wants a new "i7 920" or whatever i want to be able to sellect all motherboards for socket 1366, which is impossible because all the data is stored in one field. I know it's possible to select all motherboards form the DB and let PHP figure out which ones are for socket 1366 but i was wondering, is there a better solution?

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• Best way to store data in database when you don't know the type

  - by stiank81

  I have a table in my database that represents datafields in a custom form. The DataField gives some representation of what kind of control it should be represented with, and what value type it should take. Simplified you can say that I have 2 entities in this table - Textbox taking any string and Textbox only taking numbers. Now I have the different values stored in a separate table, referencing the datafield definition. What is the best way to store the data value here, when the type differs? One possible solution is to have the FieldValue table hold one field per possible value type. Now this would certainly be redundant, but at least I would get the value stored in its correct form - simplifying queries later. FieldValue ---------- Id DataFieldId IntValue DoubleValue BoolValue DataValue .. Another possibility is just storing everything as String, and casting this in the queries. I am using .Net with NHibernate, and I see that at least here there is a Projections.Cast that can be used to cast e.g. string to int in the query. Either way in these two solutions I need to know which type to use when doing the query, but I will know that from the DataField, so that won't be a problem. Anyway; I don't think any of these solutions sounds good. Are they? Or is there a better way?

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