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• SqlMetal, Sql Server 2008 database, Table with HierachyID, dal cs file is created sometimes ?

  - by judek.mp

  I have 2 databases with a 2 tables with HierachyID fields. For one database I can get a dal cs file, for the other database I cannot get a dal cs file ? HBus is a database I can get the dal cs for, ... SqlMetal /server:.\SQLSERVER2008 /database:HBus /code:HBusDC.cs /views /functions /sprocs /namespace:HBusDC /context:HBusDataContext This kicks me out a file, ... which works, but excludes the HierarchyID field for the table and includes all other fields for that table. This is OK I do not mind. The above cmd line kicks out an warning but still produces a file, like so SqlMetal /server:.\SQLSERVER2008 /database:HBus /code:HBusDC.cs /views /functions /sprocs /namespace:HBusDC /context:HBusDataContext Microsoft (R) Database Mapping Generator 2008 version 1.00.30729 for Microsoft (R) .NET Framework version 3.5 Copyright (C) Microsoft Corporation. All rights reserved. Warning : SQM1021: Unable to extract column 'OrgNode' of Table 'dbo.HMsg' from SqlServer because the column's DbType is a user-defined type (UDT). Warning : SQM1021: Unable to extract column 'OrgNode' of Table 'dbo.vwHMsg' from SqlServer because the column's DbType is a user-defined type (UDT). HMsg is a table with a HierarchyID field. I have another database, Elf, almost the same thing but I get a warning and an Error when using sql metal and I do not get a dal cs file ... SqlMetal /server:.\SQLSERVER2008 /database:Elf /code:ElfDataContextDal.cs /views /functions /sprocs /namespace:HBusDC /context:HBusDataContext An error as well as the warning and the cs file fails to appear on my disc, ... :-( SqlMetal /server:.\SQLSERVER2008 /database:Elf /code:ElfDataContextDal.cs /views /functions /sprocs /namespace:HBusDC /context:HBusDataContext Microsoft (R) Database Mapping Generator 2008 version 1.00.30729 for Microsoft (R) .NET Framework version 3.5 Copyright (C) Microsoft Corporation. All rights reserved. Warning : SQM1021: Unable to extract column 'OrgNode' of Table 'dbo.EntityLink' from SqlServer because the column's DbType is a user-defined type (UDT). Error : Requested value 'ELF.SYS.HIERARCHYID' was not found. The fields are declared the same way in Elf db OrgNode [HierarchyID] null , in HBus db ... OrgNode [HierarchyID] null , Both databases are in the same instance of sql server 2008, so the HierarchyID is an inbuilt type, neither db has HierarchyID udt ,... cheers in advance for any replies ...

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• ODBC: when is the best time to create my database?

  - by mawg

  I have a windows program which generates PGP forms which will be filled in later. Those PHP forms will populate a database. It looks very much like MySql, but I can't be certain, so let's call it ODBC. And, yes, it does have to be a windows program. There will also be PHP forms which query the database - examine which tables and fields it contains and then generates forms which can be used to search the database (e.g, it finds a table with fields "employee_name", etc and generates a form which lets you search based on employee name. Let's call that design time and run time. At design time, some manager or IT guy or similar gets to define the nature of the database and at runtime 1) a worker fills in the form daily and 2) management can extract reports. Here's my question: given that the database is defined at "design time" (and populated at run time), where and how is best to do so? 1 I could use an ODBC interface from the windows program, but I am having difficulty finding something good to work with Delphi. Things like ADO and firebird tend to expect you to already have a database and allow you to manipulate it, but I can find no code example of how to create a database and some tables, so ... 2 I could used DOS commands from Delphi in my windows program. I just tried and got a response to MySql --version, but am not sure if MySql etc are more interactive. That is, can I use a script file or a very long stacked command with semicolons and returns separating? e.g 'CREATE DATABASE db; CREATE TABLE t1;' 3) Since the best way to work with databases seems to be PHP, perhaps my windows program could spit out a PHP page which would, when run in a browser, create the database. I have tried to make this as uncomplicated as I can, but please feel free to ask questions. It may be that there are several valid ways, but there is probably one 'better' solution in terms of ease of implementation or maintenance. Better scratch option 3. What if the user later wants to come back and have the windows program change the input form? It needs to update the database too.

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• Big Data – Evolution of Big Data – Day 3 of 21

  - by Pinal Dave

  In yesterday’s blog post we answered what is the Big Data. Today we will understand why and how the evolution of Big Data has happened. Though the answer is very simple, I would like to tell it in the form of a history lesson. Data in Flat File In earlier days data was stored in the flat file and there was no structure in the flat file.  If any data has to be retrieved from the flat file it was a project by itself. There was no possibility of retrieving the data efficiently and data integrity has been just a term discussed without any modeling or structure around. Database residing in the flat file had more issues than we would like to discuss in today’s world. It was more like a nightmare when there was any data processing involved in the application. Though, applications developed at that time were also not that advanced the need of the data was always there and there was always need of proper data management. Edgar F Codd and 12 Rules Edgar Frank Codd was a British computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational databases. He presented 12 rules for the Relational Database and suddenly the chaotic world of the database seems to see discipline in the rules. Relational Database was a promising land for all the unstructured database users. Relational Database brought into the relationship between data as well improved the performance of the data retrieval. Database world had immediately seen a major transformation and every single vendors and database users suddenly started to adopt the relational database models. Relational Database Management Systems Since Edgar F Codd proposed 12 rules for the RBDMS there were many different vendors who started them to build applications and tools to support the relationship between database. This was indeed a learning curve for many of the developer who had never worked before with the modeling of the database. However, as time passed by pretty much everybody accepted the relationship of the database and started to evolve product which performs its best with the boundaries of the RDBMS concepts. This was the best era for the databases and it gave the world extreme experts as well as some of the best products. The Entity Relationship model was also evolved at the same time. In software engineering, an Entity–relationship model (ER model) is a data model for describing a database in an abstract way. Enormous Data Growth Well, everything was going fine with the RDBMS in the database world. As there were no major challenges the adoption of the RDBMS applications and tools was pretty much universal. There was a race at times to make the developer’s life much easier with the RDBMS management tools. Due to the extreme popularity and easy to use system pretty much every data was stored in the RDBMS system. New age applications were built and social media took the world by the storm. Every organizations was feeling pressure to provide the best experience for their users based the data they had with them. While this was all going on at the same time data was growing pretty much every organization and application. Data Warehousing The enormous data growth now presented a big challenge for the organizations who wanted to build intelligent systems based on the data and provide near real time superior user experience to their customers. Various organizations immediately start building data warehousing solutions where the data was stored and processed. The trend of the business intelligence becomes the need of everyday. Data was received from the transaction system and overnight was processed to build intelligent reports from it. Though this is a great solution it has its own set of challenges. The relational database model and data warehousing concepts are all built with keeping traditional relational database modeling in the mind and it still has many challenges when unstructured data was present. Interesting Challenge Every organization had expertise to manage structured data but the world had already changed to unstructured data. There was intelligence in the videos, photos, SMS, text, social media messages and various other data sources. All of these needed to now bring to a single platform and build a uniform system which does what businesses need. The way we do business has also been changed. There was a time when user only got the features what technology supported, however, now users ask for the feature and technology is built to support the same. The need of the real time intelligence from the fast paced data flow is now becoming a necessity. Large amount (Volume) of difference (Variety) of high speed data (Velocity) is the properties of the data. The traditional database system has limits to resolve the challenges this new kind of the data presents. Hence the need of the Big Data Science. We need innovation in how we handle and manage data. We need creative ways to capture data and present to users. Big Data is Reality! Tomorrow In tomorrow’s blog post we will try to answer discuss Basics of Big Data Architecture. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• alphanumeric and special character sorting

  - by Kaushik Gopal

  Hi ppl, I wanted to know the different standards of sorting. To be more specific take the sample set: (Please note there's capitals, small letters, special characters, null values and numbers here) A a 3F Zx - 1Ad NULL How would the Oracle Database sort this by default? How would LINQ sort this by default? How would db2 sort this by default? (the following may get even more vague) How does the Windows platform sort this? (I mean say you have a couple of filenames, by default how would this get treated in a name sort) How does the *nix platform sort this? Is there some sort of standard for alphanumeric/special character sorting? The Windows operating system orders with numbers first, then alphabets. The Oracle database however treats alphabets first. I'm not sure of the *nix platform. It would be nice to have one place to know all these rules for the most common platforms (listed in questions above). Would the gurus throw some light on this topic? Cheers, K

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• Complex Query on cassandra

  - by Sadiqur Rahman

  I have heard on cassandra database engine few days ago and searching for a good documentation on it. after studying on cassandra I got cassandra is more scalable than other data engine. I also read on Amazon SimpleDB but as SimpleDB has a limitation 10GB/table and Google Datastore is slower than Amazon SimpleDB, I prefer not to use them (Google Datastore, Amazon SimpleDB). So for making our site scaled specially high write rates with massive data, I like to use Cassandra as our Data Engine. But before starting using cassandra I am confused on "How to handle complex data using casssandra". I am giving you the MySQL database structure below, Please read this and give me a good suggestion. Users Table hasColum ID Primary hasColum email Unique hasColum FirstName hasColum LastName Category Table hasColum ID Primary hasColum Parent hasColum Category Posts Table hasColum ID Primary hasColum UID Index foreign key linked to users-ID hasColum CID Index foreign key linked to Category-ID hasColum Title hasColum Post Index hasColum PunDate Comments hasColum ID primary hasColum UID Index foreign key linked to users-ID hasColum PID Index foreign key linked to Posts-ID hasColum Comment User Group hasColum ID primary hasColum Name UserToGroup Table (for many to many relation only) hasColum UID foreign key linked to Users-ID hasColum GID foreign key linked to Group-ID Finally for your information, I like to use SimpleCassie PHP Class http://code.google.com/p/simpletools-php/ So, it will be very helpful if you can give me example using SimpleCassie

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• NHibernate query with Projections.Cast to DateTime

  - by stiank81

  I'm experimenting with using a string for storing different kind of data types in a database. When I do queries I need to cast the strings to the right type in the query itself. I'm using .Net with NHibernate, and was glad to learn that there exists functionality for this. Consider the simple class: public class Foo { public string Text { get; set; } } I successfully use Projections.Cast to cast to numeric values, e.g. the following query correctly returns all Foos with an interger stored as int - between 1-10. var result = Session.CreateCriteria<Foo>() .Add(Restrictions.Between(Projections.Cast(NHibernateUtil.Int32, Projections.Property("Text")), 1, 10)) .List<Foo>(); Now if I try using this for DateTime I'm not able to make it work no matter what I try. Why?! var date = new DateTime(2010, 5, 21, 11, 30, 00); AddFooToDb(new Foo { Text = date.ToString() } ); // Will add it to the database... var result = Session .CreateCriteria<Foo>() .Add(Restrictions.Eq(Projections.Cast(NHibernateUtil.DateTime, Projections.Property("Text")), date)) .List<Foo>();

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• Drop Down list null value not working for selected text c#?

  - by Tamara JQ

  Hi guys, Basically I have a drop down list which is populated with text and values depending on a selected index of a radio button list. The code is as follows: protected void RBLGender_SelectedIndexChanged(object sender, EventArgs e) { DDLTrous.Items.Clear(); DDLShoes.Items.Clear(); if (RBLGender.SelectedValue.Equals("Male")) { String[] MaleTrouserText = {"[N/A]", "28\"", "30\"", "32\"", "34\"", "36\"", "38\"", "40\"", "42\"", "44\"", "48\""}; String[] MaleTrouserValue = { null, "28\"", "30\"", "32\"", "34\"", "36\"", "38\"", "40\"", "42\"", "44\"", "48\"" }; String[] MaleShoeText = { "[N/A]", "38M", "39M", "40M", "41M", "42M", "43M", "44M", "45M", "46M", "47M" }; String[] MaleShoeValue = { null, "38M", "39M", "40M", "41M", "42M", "43M", "44M", "45M", "46M", "47M" }; for (int i = 0; i < MaleTrouserText.Length; i++) { ListItem MaleList = new ListItem(MaleTrouserText[i], MaleTrouserValue[i]); DDLTrous.Items.Add(MaleList); } for (int i = 0; i < MaleShoeText.Length; i++) { ListItem MaleShoeList = new ListItem(MaleShoeText[i], MaleShoeValue[i]); DDLShoes.Items.Add(MaleShoeList); } } else if (RBLGender.SelectedValue.Equals("Female"))` When the text '[N/A]' is selected I want the value NULL to be inserted into the database. At present when '[N/A]' is selected the value entered into the database is [N/A] does anyone know why? Thanks in advance.

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• doublechecking: no db-wide 'unicode switch' for sql server in the foreseeable future, i.e. like Orac

  - by user72150

  Hi all, I believe I know the answer to this question, but wanted to confirm: Question Does Sql server (or will it in the foreseeable future), offer a database-wide "unicode switch" which says "store all characters in unicode (UTF-16, UCS-2, etc)", i.e. like Oracle. The Context Our application has provided "CJK" (Chinese-Japanese-Korean) support for years--using Oracle as the db store. Recently folks have been asking for the same support in sql server. We store our db schema definition in xml and generate the vendor-specific definitions (oracle, sql server) using vendor-specific xsl. We can make the change easily. The problem is for upgrades. Generated scripts would need to change the column types for 100+ columns from varchar to nvarchar, varchar(max) to nvarchar(max), etc. These changes require dropping and recreating indexes and foreign keys if the any indexes/fk's exist on the column. Non-trivial. Risky. DB-wide character encodings for us would eliminate programming changes. (I.e. we would not to change the column types from varchar to nvarchar; sql server would correctly store unicode data in varchar columns). I had thought that eventually sql server would "see the light" and allow storing unicode in varchar/clob columns. Evidently not yet. Recap So just to triple check: does mssql offer a database-wide switch for character encoding? Will it in SQL2008R3? or 2010? thanks, bill

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• Application passwords and SQLite security

  - by Bryan

  I have been searching on google for information regarding application passwords and SQLite security for some time, and nothing that I have found has really answered my questions. Here is what I am trying to figure out: 1) My application is going to have an optional password activity that will be called when the application is first opened. My questions for this are a) If I store the password via android preference or SQLite database, how can I ensure security and privacy for the password, and b) how should password recovery be handled? Regarding b) from above, I have thought about requiring an email address when the password feature is enabled, and also a password hint question for use when requesting password recovery. Upon successfully answering the hint question, the password is then emailed to the email address that was submitted. I am not completely confident in the security and privacy of the email method, especially if the email is sent when the user is connected to an open, public wireless network. 2) My application will be using an SQLite database, which will be stored on the SD card if the user has one. Regardless of whether it is stored on the phone or the SD card, what options do I have for data encryption, and how does that affect the application performance? Thanks in advance for time taken to answer these questions. I think that there may be other developers struggling with the same concerns.

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• Data Access Layer, Best Practices

  - by labratmatt

  I'm looking for input on the best way to refactor the data access layer (DAL) in my PHP based web app. I follow an MVC pattern: PHP/HTML/CSS/etc. views on the front end, PHP controllers/services in the middle, and a PHP DAL sitting on top of a relational database in the model. Pretty standard stuff. Things are working fine, but my DAL is getting large (codesmell?) and becoming a bit unwieldy. My DAL contains almost all of the logic to interface with my database and is full of functions that look like this: function getUser($user_id) { $statement = "select id, name from users where user_id=:user_id"; PDO builds statement and fetchs results as an array return $array_of_results_generated_by_PDO_fetch_method; } Notes: The logic in my controller only interacts with the model using functions like the above in the DAL I am not using a framework (I'm of the opinion that PHP is a templating language and there's no need to inject complexity via a framework) I generally use PHP as a procedural language and tend to shy away from its OOP approach (I enjoy OOP development but prefer to keep that complexity out of PHP) What approaches have you taken when your DAL has reached this point? Do I have a fundamental design problem? Do I simply need to chop my DAL into a number of smaller files (logically divide it)? Thanks.

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• Integer Surrogate Key?

  - by CitadelCSAlum

  I need something real simple, that for some reason I am unable to accomplish to this point. I have also been unable to Google the answer surprisingly. I need to number the entries in different tables uniquely. I am aware of AUTO INCREMENT in MySQL and that it will be involved. My situation would be as follows If I had a table like Table EXAMPLE ID - INTEGER FIRST_NAME - VARCHAR(45) LAST_NAME - VARCHAR(45) PHONE - VARCHAR(45) CITY - VARCHAR(45) STATE - VARCHAR(45) ZIP - VARCHAR(45) This would be the setup for the table where ID is an integer that is auto-incremented every time an entry is inserted into the table. The thing I need is that I do not want to have to account for this field when inserting data into the database. From my understanding this would be a surrogate key, that I can tell the database to automatically increment and I do not have to include it in the INSERT STATEMENT so instead of INSERT INTO EXAMPLE VALUES (2,'JOHN','SMITH',333-333-3333,'NORTH POLE'.... I can leave out the first ID column and just write something like INSERT INTO EXAMPLE VALUES ('JOHN','SMITH'.....etc) Notice I Wouldnt have to define the ID column... I know this is a very common task to do, but for some reason I cant get to the bottom of it. I am using MySQL, just to clarify. Thanks alot

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• How should I manage my many-to-many relationships?

  - by wes

  Hello all, I have a database containing a couple tables: files and users. This relationship is many-to-many, so I also have a table called users_files_ref which holds foreign keys to both of the above tables. Here's the schema of each table: files - file_id, file_name users - user_id, user_name users_files_ref - user_file_ref_id, user_id, file_id I'm using Codeigniter to build a file host application, and I'm right in the middle of adding the functionality that enables users to upload files. This is where I'm running into my problem. Once I add a file to the files table, I will need that new file's id to update the users_files_ref table. Right now I'm adding the record to the files table, and then I imagined I'd run a query to grab the last file added, so that I can get the ID, and then use that ID to insert the new users_files_ref record. I know this will work on a small scale, but I imagine there is a better way of managing these records, especially in a heavy-traffic scenario. I am new to relational database stuff but have been around PHP for a while, so please bear with me here :-) I have primary and foreign keys set up correctly for the files, users, and users_files_ref tables, I'm just wondering how to manage the adding of file records for this scenario? Thanks for any help provided, it's much appreciated. -Wes

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• How to make a product catalog in C#?

  - by Ervin

  I need to develop a product catalog (about 4000 products) application, which would be given to clients on CD or DVD. The catalog exists in webpage format using PHP and MySQL. IMPORTANT: the application is given to clients who maight have old PC, old System. For minimal requirements I would put Windows XP and Internet Explorer 6 (if needed). I need the following features: 1 search option (after productID AND after keyword) 2 print option (by selecting multiple products) 3 shopping cart (making a list which will be sent to an email address if there is any Internet Connection on the computer) When I was asked to do it I had 2 days to realise a very basic version, so I took the whole website and exported it in HTML pages, and developed an application in C# which contains an embeded browser. So the whole website is now static and put on a CD. Everything fine so far. Now here are the problems: 1. the search option was realized by parsing the html files and reading the productID or looking for keywords inside of them. Put on a CD it was extremely slow (searching in 600MB of html files). FOR THIS I WOULD NEED A SOLUTION WITH A STATIC DATABASE (USING ACCESS OR SOMETHING) TO HAVE INDEXED ROWS, SO THE SEARCH COULD BE A VERY FAST ONE. 2. the printing option was a simply call of the embeded Internet Explorer print functions. Here are two problems: a) user needs IE7 for printing the website scaled (FIT TO PAGE), otherwise the edges of the page are cut down. b) users of this app does not have even the basic PC usage skills, so they can't set the printing settings, so there will appear in header and footer the page numbers and titles. QUESTION: can I set these settings from CSS for printing? 3. couldn't make a a shopping cart as I don't use a database, so I have static websites and content is inside the HTML. QUESTION: WHICH ARE THE BEST SOLUTIONS FOR THE PROBLEMS DESCRIBED ABOVE? PLEASE ANSWER EVEN IF YOUR ANSWER IS FOR ONE QUESTION ONLY. THANKS

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• Starting with versioning mysql schemata without overkill. Good solutions?

  - by tharkun

  I've arrived at the point where I realise that I must start versioning my database schemata and changes. I consequently read the existing posts on SO about that topic but I'm not sure how to proceed. I'm basically a one man company and not long ago I didn't even use version control for my code. I'm on a windows environment, using Aptana (IDE) and SVN (with Tortoise). I work on PHP/mysql projects. What's a efficient and sufficient (no overkill) way to version my database schemata? I do have a freelancer or two in some projects but I don't expect a lot of branching and merging going on. So basically I would like to keep track of concurrent schemata to my code revisions. [edit] Momentary solution: for the moment I decided I will just make a schema dump plus one with the necessary initial data whenever I'm going to commit a tag (stable version). That seems to be just enough for me at the current stage.[/edit] [edit2]plus I'm now also using a third file called increments.sql where I put all the changes with dates, etc. to make it easy to trace the change history in one file. from time to time I integrate the changes into the two other files and empty the increments.sql[/edit]

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• How to organize integrity tests and code unit tests?

  - by karlthorwald

  I have several files with code testing code (which uses a "unittest" class). Later I found it would be nice to test database integrity also. I put this into a separate directory tree. (Things like the keys have correct format, parent and child nodes are pointing correctly and such.) I use the same unittest class for the integrity tests. Now I wonder if it makes really sense to keep this separate. To test the integrity of data I often duplicate parts of code that I use to test the code that handles the data. But it is not the same. The code tests use test databases (that get deleted after each test) and the integrity tests connect to the live data and analyze it. The integrity tests I want to call from cron and send an alarm if something happens in the live database. How would you handle that? Are there standards for such a setup? What is your experience? My tendency is to put everything in the same file, which would result in the code tests also being executed by the cron on the production environment.

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• storing data at remote server using php

  - by VIPUL GOYAL

  I want to send data to php file and execute insert query in it to store data in database. When i execute this code, it executes but database does not get updated. Code of PHP file Java code------------------------------Remote.java------------------------------ public class Remote extends Activity { EditText name; Button s; String r; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); name= (EditText)findViewById(R.id.editText1); s=(Button)findViewById(R.id.button1); s.setOnClickListener(new OnClickListener() { public void onClick(View v) { try { r = name.getText().toString(); ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>(); postParameters.add(new BasicNameValuePair("username", r)); CustomHttpClient.executeHttpPost("http://vipul.eu5.org/abc.php", postParameters); //Enetr Your remote PHP,ASP, Servlet file link } catch (Exception e) { e.printStackTrace(); } } }); } } -----------------------------CustomHttpClient.java---------------------------- public class CustomHttpClient { private static HttpClient getHttpClient() { if (mHttpClient == null) { mHttpClient = new DefaultHttpClient(); final HttpParams params = mHttpClient.getParams(); HttpConnectionParams.setConnectionTimeout(params, HTTP_TIMEOUT); HttpConnectionParams.setSoTimeout(params, HTTP_TIMEOUT); ConnManagerParams.setTimeout(params, HTTP_TIMEOUT); } return mHttpClient; } /** * Performs an HTTP Post request to the specified url with the * specified parameters. * * @param url The web address to post the request to * @param postParameters The parameters to send via the request * @return The result of the request * @throws Exception */ public static void executeHttpPost(String url, ArrayList postParameters) throws Exception { try { HttpClient client = getHttpClient(); HttpPost request = new HttpPost(url); UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(postParameters); request.setEntity(formEntity); HttpResponse response = client.execute(request); } catch(Exception e) { } } }

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• SQL Concurrent test update question

  - by ptoinson

  Howdy Folks, I have a SQLServer 2008 database in which I have a table for Tags. A tag is just an id and a name. The definition of the tags table looks like: CREATE TABLE [dbo].[Tag]( [ID] [int] IDENTITY(1,1) NOT NULL, [Name] [varchar](255) NOT NULL CONSTRAINT [PK_Tag] PRIMARY KEY CLUSTERED ( [ID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ) Name is also a unique index. further I have several processes adding data to this table at a pretty rapid rate. These processes use a stored proc that looks like: ALTER PROC [dbo].[lg_Tag_Insert] @Name varchar(255) AS DECLARE @ID int SET @ID = (select ID from Tag where Name=@Name ) if @ID is null begin INSERT Tag(Name) VALUES (@Name) RETURN SCOPE_IDENTITY() end else begin return @ID end My issues is that, other than being a novice at concurrent database design, there seems to be a race condition that is causing me to occasionally get an error that I'm trying to enter duplicate keys (Name) into the DB. The error is: Cannot insert duplicate key row in object 'dbo.Tag' with unique index 'IX_Tag_Name'. This makes sense, I'm just not sure how to fix this. If it where code I would know how to lock the right areas. SQLServer is quite a different beast. First question is what is the proper way to code this 'check, then update pattern'? It seems I need to get an exclusive lock on the row during the check, rather than a shared lock, but it's not clear to me the best way to do that. Any help in the right direction will be greatly appreciated. Thanks in advance.

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• Model login constraints based on time

  - by DaDaDom

  Good morning, for an existing web application I need to implement "time based login constraints". It means that for each user, later maybe each group, I can define timeslots when they are (not) allowed to log in into the system. As all data for the application is stored in database tables, I need to somehow create a way to model this idea in that way. My first approach, I will try to explain it here: Create a tree of login constraints (called "timeslots") with the main "categories", like "workday", "weekend", "public holiday", etc. on the top level, which are in a "sorted" order (meaning "public holiday" has a higher priority than "weekday") for each top level node create subnodes, which have a finer timespan, like "monday", "tuesday", ... below that, create an "hour" level: 0, 1, 2, ..., 23. No further details are necessary. set every member to "allowed" by default For every member of the system create a 1:n relationship member:timeslots which defines constraints, e.g. a member A may have A:monday-forbidden and A:tuesday-forbidden Do a depth-first search at every login and check if the member has a constraint. Why a depth first search? Well, I thought that it may be that a member has the rules: A:monday->forbidden, A:monday-10->allowed, A:mondey-11->allowed So a login on monday at 12:30 would fail, but one at 10:30 succeed. For performance reasons I could break the relational database paradigm and set a flag for every entry in the member-to-timeslots-table which is set to true if the member has information set for "finer" timeslots, but that's a second step. Is this model in principle a good idea? Are there existing models? Thanks.

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• How to organize live data integrity tests and code unit tests?

  - by karlthorwald

  I have several files with code testing code (which uses a "unittest" class). Later I found it would be nice to test database integrity also. I put this into a separate directory tree. (Things like the keys have correct format, parent and child nodes are pointing correctly and such.) I use the same unittest class for the integrity tests. Now I wonder if it makes really sense to keep this separate. To test the integrity of data I often duplicate parts of code that I use to test the code that handles the data. But it is not the same. The code tests use test databases (that get deleted after each test) and the integrity tests connect to the live data and analyze it. The integrity tests I want to call from cron and send an alarm if something happens in the live database. How would you handle that? Are there standards for such a setup? What is your experience? My tendency is to put everything in the same file, which would result in the code tests also being executed by the cron on the production environment.

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• iPhone Core Data does not refresh table

  - by Brian515

  Hi all, I'm trying to write an application with Core Data, and I have been able to successfully read and write to the core data database. However, if I write to the database in one view controller, my other view controllers will not see the change until the app is closed then reopened again. This is really frustrating. I'm not entirely sure how to get the refresh - (void)refreshObject:(NSManagedObject *)object mergeChanges:(BOOL)flag method to work. How do I get a reference to my managed object? Anyways, here's the code I'm using to read the data back. This is in the viewDidLoad method. NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Website" inManagedObjectContext:managedObjectContext]; [request setEntity:entity]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"siteName" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [sortDescriptor release]; [sortDescriptors release]; NSError *error = nil; NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy]; if(mutableFetchResults == nil) { //Handle the error } [self setNewsTitlesArray:mutableFetchResults]; [mutableFetchResults release]; [request release]; [newsSourcesTableView reloadData]; Thanks for help in advance!

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• rails Creating a model instance automatically when another is created

  - by bob

  Hello I have a user model and a ratings model. Whenever a new user is created I want to create a new feedback model with it automatically. Each user model has one feedback model and each feedback model has many ratings. My Classes class User < ActiveRecord::Base end class Feedback < ActiveRecord::Base belongs_to :user has_many :ratings end class Rating < ActiveRecord::Base belongs_to :feedback end My database tables -user doesn't have anything special -feedback has user_id. This user_id should be the same as the user that has just been created. For example, user_id of 1 is created, then a feedback model should be created that belongs to user_id of 1. So the user_id column in the feedback database will also be 1. - Rating has a feedback_id and a user_id the user_id in this case is the id of the person who submitted the rating. I am having it assigned through the build command. I believe my process is correct here. The Goal The goal is to have each user have a feedback table that has many ratings from other users. So if someone goes to the feedback page, they will see all the ratings given and by who. Is there a better way to approach this? How do you create a model of feedback with the same id as the user being created right when a new user is created. The idea is that when a user is created a feedback is created associated with that user so people can then go to http://localhost:3000/users/1/feedback/ and submit new ratings. I'm trying to bypass having a user rate another user with just a ratings model because I'm not sure how to do it.

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• Would this method work to scale out SQL queries?

  - by David

  I have a database containing a single huge table. At the moment a query can take anything from 10 to 20 minutes and I need that to go down to 10 seconds. I have spent months trying different products like GridSQL. GridSQL works fine, but is using its own parser which does not have all the needed features. I have also optimized my database in various ways without getting the speedup I need. I have a theory on how one could scale out queries, meaning that I utilize several nodes to run a single query in parallel. The idea is to take an incoming SQL query and simply run it exactly like it is on all the nodes. When the results are returned to a coordinator node, the same query is run on the union of the resultsets. I realize that an aggregate function like average need to be rewritten into a count and sum to the nodes and that the coordinator divides the sum of the sums with the sum of the counts to get the average. What kinds of problems could not easily be solved using this model. I believe one issue would be the count distinct function. Edit: I am getting so many nice suggestions, but none have addressed the method.

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• PHP: tips/resources/patterns for learning to implement a basic ORM

  - by BoltClock

  I've seen various MVC frameworks as well as standalone ORM frameworks for PHP, as well as other ORM questions here; however, most of the questions ask for existing frameworks to get started with, which is not what I'm looking for. (I have also read this SO question but I'm not sure what to make of it, and the answers are vague.) Instead, I figured I'd learn best by getting my hands dirty and actually writing my own ORM, even a simple one. Except I don't really know how to get started, especially since the code I see in other ORMs is so complicated. With my PHP 5.2.x (this is important) MVC framework I have a basic custom database abstraction layer, that has: Very simple methods like connect($host, $user, $pass, $base), query($sql, $binds), etc Subclasses for each DBMS that it supports A class (and respective subclasses) to represent SQL result sets But does not have: Active Record functionality, which I assume is an ORM thing (correct me if I'm wrong) I've read up a little about ORM, and from my understanding they provide a means to further abstract data models from the database itself by representing data as nothing more than PHP-based classes/objects; again, correct me if I am wrong or have missed out in any way. Still, I'd like some simple tips from anyone else who's dabbled more or less with ORM frameworks. Is there anything else I need to take note of, simple example code for me to refer to, or resources I can read? Thanks a lot in advance!

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• How do I populate a MEF plugin with data that is not hard coded into the assembly?

  - by hjoelr

  I am working on a program that will communicate with various pieces of hardware. Because of the varied nature of the items it communicates and controls, I need to have a different "driver" for each different piece of hardware. This made me think that MEF would be a great way to make those drivers as plugins that can be added even after the product has been released. I've looked at a lot of examples of how to use MEF, but the question that I haven't been able to find an answer to is how to populate a MEF plugin with external data (eg. from a database). All the examples I can find have the "data" hard-coded into the assembly, like the following example: [Export( typeof( IRule ) )] public class RuleInstance : IRule { public void DoIt() {} public string Name { get { return "Rule Instance 3"; } } public string Version { get { return "1.1.0.0"; } } public string Description { get { return "Some Rule Instance"; } } } What if I want Name, Version and Description to come from a database? How would I tell MEF where to get that information? I may be missing something very obvious, but I don't know what it is. Thanks! Joel

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• MYSQL not running on Ubuntu OS - Error 2002.

  - by mgj

  Hi, I am a novice to mysql DB. I am trying to run the MYSQL Server on Ubuntu 10.04. Through Synaptic Package Manager I am have installed the mysql version: mysql-client-5.1 I wonder that how was the database password set for the mysql-client software that I installed through the above way.It would be nice if you could enlighten me on this. When I tried running this database, I encountered the error given below: mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) mohnish@mohnish-laptop:/var/lib$ I referred to a similar question posted by another user. I didn't find a solution through the proposed answers. For instance when I tried the solutions posted for the similar question I got the following: mohnish@mohnish-laptop:/var/lib$ service start mysqld start: unrecognized service mohnish@mohnish-laptop:/var/lib$ ps -u mysql ERROR: User name does not exist. ********* simple selection ********* ********* selection by list ********* -A all processes -C by command name -N negate selection -G by real group ID (supports names) -a all w/ tty except session leaders -U by real user ID (supports names) -d all except session leaders -g by session OR by effective group name -e all processes -p by process ID T all processes on this terminal -s processes in the sessions given a all w/ tty, including other users -t by tty g OBSOLETE -- DO NOT USE -u by effective user ID (supports names) r only running processes U processes for specified users x processes w/o controlling ttys t by tty *********** output format ********** *********** long options *********** -o,o user-defined -f full --Group --User --pid --cols --ppid -j,j job control s signal --group --user --sid --rows --info -O,O preloaded -o v virtual memory --cumulative --format --deselect -l,l long u user-oriented --sort --tty --forest --version -F extra full X registers --heading --no-heading --context ********* misc options ********* -V,V show version L list format codes f ASCII art forest -m,m,-L,-T,H threads S children in sum -y change -l format -M,Z security data c true command name -c scheduling class -w,w wide output n numeric WCHAN,UID -H process hierarchy mohnish@mohnish-laptop:/var/lib$ which mysql /usr/bin/mysql mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) I even tried referring to http://forums.mysql.com/read.php?11,27769,84713#msg-84713 but couldn't find anything useful. Please let me know how I could tackle this error. Thank you very much..

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