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• #define vs enum in an embedded environment (How do they compile?)

  - by Alexander Kondratskiy

  This question has been done to death, and I would agree that enums are the way to go. However, I am curious as to how enums compile in the final code- #defines are just string replacements, but do enums add anything to the compiled binary? Or are they both equivalent at that stage. When writing firmware and memory is very limited, is there any advantage, no matter how small, to using #defines? Thanks! EDIT: As requested by the comment below, by embedded, I mean a digital camera. Thanks for the answers! I am all for enums!

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• Designing a recipe database that needs to include ingredients as well as sub-recipes

  - by VinceL

  I am designing a recipe database that needs to be very flexible as it is going to be communicating directly with our back-of-house inventory system. This is what I have so far in regards to the tables: Recipe: this table will contain the recipe date: the name, steps needed to cook, etc. Ingredients/Inventory: this is our back of house inventory, so this will have the information about each product that will be used in our recipes. Recipe Line Item: This is the tricky table, I want to be able link to the ingredients here as well as the quantity needed for the recipe, but I also need to be able to directly include recipes from the recipe table (such as marinara sauce that we make in-house), and that is why I am having trouble figuring out the best way to design this table. Basically, the recipe line item table needs to be able to link to either the ingredients table or the recipe table depending on which line item is needed and I want to know what would be the most effective way to handle that. Thank you so much in advance!

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• How to get started with embedded systems in the aircraft or submarine industries?

  - by Jason

  Hi, Not 100% sure how to frame this question but here goes... I currently work as a Rails developer but want to work on more substancial / "meaty" projects and have always been very interested in embedded systems, especially systems that run on aircraft and especially submarines.....I know strange combination. I have been doing some searching & found lockheed martin produces a lot of underwater systems for various navys around the world e.g. http://www.naval-technology.com/projects/nssn/ However, there is very little information about what software is used within these systems, what OS's they use or anything else "technical", presume there is a lot of C / C++ involved but that is just a guess... so its hard to know where to even begin learning what is required to potential work in these areas. Just wondering if anyone has any experiance working with or more information about embeddeed systems in either the airline (onboard flight systems) or especially submarine systems? Thanks!

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• How to test reliability of my own (small) embedded operating system ?

  - by TridenT

  I've written a small operating system for embedded project running on small to medium target. I added some automated unit test with a high test code coverage (95%), but the scope is only the static part. I got some code metrics as complexity and readability. I'm testing my code with a rule checker with MiSRA support, and of course fixed all warnings. I'm testing the code with a static analyzer and again fixed all warnings. What can I do now to test - and improve - the reliability of my OS ? How about the dynamic part ?

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• Database indexes and their Big-O notation

  - by miket2e

  I'm trying to understand the performance of database indexes in terms of Big-O notation. Without knowing much about it, I would guess that: Querying on a primary key or unique index will give you a O(1) lookup time. Querying on a non-unique index will also give a O(1) time, albeit maybe the '1' is slower than for the unique index (?) Querying on a column without an index will give a O(N) lookup time (full table scan). Is this generally correct ? Will querying on a primary key ever give worse performance than O(1) ? My specific concern is for SQLite, but I'd be interested in knowing to what extent this varies between different databases too.

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• C# ASP.NET Update database with datatable

  - by Sir Graystar

  Scenario: I'm just trying to update my database with the changes made by the user to their information. Here is my code: SqlCommandBuilder cb = new SqlCommandBuilder(da); dt.Rows[0][2] = txtname.Text; dt.Rows[0][3] = txtinterests.Text; dt.Rows[0][4] = txtlocation.Text; da.SelectCommand = new SqlCommand(sqlcommand, conn); da.Update(dt); I know its going to be something obvious, but what have I missed? There are no errors, everything compiles correctly, but nothing happens. The record remains unchanged.

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• what's the best practice to config Hibernate-Spring for multiple database relationship?

  - by nazila

  We have a main mysql database which all of the applications within our organization need the data within this database. How can I config my java web application to use this database with it's specific database when I use Spring and Hibernate within my application? How can I config JPA annotations for example between CONTRACT table within my database and COUNTRY table within our main database? what's the best practice to do this?

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• Proper abstraction of the database tier in a 3 tier system?

  - by Earlz

  Hello, I am creating a 3 tier application. Basically it goes Client - (through optional server to be a thin-client) - Business Logic - Database Layer And basically making it so that there is never any skipping around. As such, I want for all of the SQL queries and such to be in the Database Layer. Well, now I'm a bit confused. I made a few static classes to start off the database tier but what should I do for the database connections? Should I just create a new database connection anytime I enter the Database Layer or would that be wasteful? Does Connection.Open() take time whenever you have a ConnectionPool? To me, it just feels wrong for the Business tier to have to pass in a IdbConnection object to the Database tier. It seems like the Database tier should handle all of that DB-specific code. What do you think? How can I do it the proper way while staying practical?

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• Single database with multiple instances of Django

  - by jwesonga

  I have a Django project where the company will have a main site like www.ourcompany.org and a bunch of sub-domains like project.ourcompany.org. Content appearing in the sub-domains like case studies should also appear in the main site. I've decided to use multiple instances of Django BUT one database for each sub-domain so that I can have some flexibility and take advantage of the Sites framework. What I'm not sure of is how to access the models across the multiple instances. If I have a model: class CaseStudy(models.Model): title=models.CharField(max_length=100) site=models.ManyToMany(Site) Do I need to create this model in every instance so that I can have access to the object?

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• Set database based on how the application was started

  - by AaronThomson

  I have two Rails applications (lets call them APP-1 and APP-2), each of them has a dependancy on a third Rails application (APP-3). I would like to be able to run the tests for APP-1 and APP-2 in parallel on my CI server. The problem is, both need to start up APP-3 and write to a DB via the APP-3. This causes conflicts and failures if the tests are run in parallel. My idea for a solution is for APP-1 and APP-2 to each start their own instance of APP-3 and to have each instance point to a different DB. Is there a way to dynamically set the DB in the database.yml of APP-3 so that it connects to a different DB depending on which APP starts it up? FYI. APP-1 and APP-2 currently start APP-3 via rake tasks.

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• Create a service that connects to remote database and uses public key encryption

  - by Leedsoft Solutions

  I have been searching all day and reading many tutorials and still I am confused. I am working on a project that has the following requirements as specified by the client (customer - not to be confused with client app): Connect to a remote server and verify that connection was successful. Connect to Web service on said server via SOAP. Authenticate with service using public key encryption Upon successful authentication, push a list of products and categories to a MSSQL database on remote server via the Web service. The client is a Winforms application written in C#. So far, I have created a WCF Service Application with separate services for the products and categories but I cannot figure the rest out. Can anyone point me in the direction of a tutorial or tutorials that cover these requirements? Many thanks in advance! Joe

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• Codeigniter database update

  - by Carry All

  The table is like this and I want to update DecryptionDate by specify ArchiveID and RecipientID this is my code $this->load->database(); $date = date("Y-m-d H:i:s"); $data = array('DecryptionDate' => $date); $array = array('ArchiveID'=>$archiveID.'','RecipientID'=>$userID.''); $this->db->where($array); $this->db->update('log', $data); if ($this->db->affected_rows() > 0) { echo "SUCCESS"; } else { echo "FAIL"; } my problem is I can update the data only when $archiveID is 911 and $userID is test01 but the program fail to update when $archiveID is 911 and $userID is test02

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• Copying a mysql database from localhost to remote server using mysqldump.exe

  - by Ankur

  I want to copy a mysql database from my local computer to a remote server. I am trying to use the mysql dump command. All the examples on the internet suggest doing something like The initial mysql> is just the prompt I get after logging in. mysql> mysqldump -u user -p pass myDBName | NewDBName.out; But when I do this I get You have an error in your SQL syntax; check the manual that corresponds ... to use near 'mysqldump -u user -p pass myDBName | NewDBName.out' Since I have already logged in do I need to use -u and -p? Not doing so gives me the same error. Can you see what is wrong?

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• Storing millions of URLs in a database for fast pattern matching

  - by Paras Chopra

  I am developing a web analytics kind of system which needs to log referring URL, landing page URL and search keywords for every visitor on the website. What I want to do with this collected data is to allow end-user to query the data such as "Show me all visitors who came from Bing.com searching for phrase that contains 'red shoes'" or "Show me all visitors who landed on URL that contained 'campaign=twitter_ad'", etc. Because this system will be used on many big websites, the amount of data that needs to log will grow really, really fast. So, my question: a) what would be the best strategy for logging so that scaling the system doesn't become a pain; b) how to use that architecture for rapid querying of arbitrary requests? Is there a special method of storing URLs so that querying them gets faster? In addition to MySQL database that I use, I am exploring (and open to) other alternatives better suited for this task.

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• MultiOS "Jet Database" for QtC++?

  - by Airjoe

  Hopefully I can articulate this well: I'm porting an application I made years ago from VB6 (I know, I know!) to QtC++. In my original application, one thing I liked was that I didn't need an actual SQL server running, I could just use MS Access .mdb files. I was wondering if something similar exists for QtC++ that will work on multiple OSes- a database stored in a file, pretty much, but that I can still run SQL queries with. Not sure if something like this exists or not, but any help appreciated, thanks!

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• How to create initializeDB() method for java database

  - by Holly

  I am working on a Java project for class and have not worked much with incorporating databases into Java. I can't find much on the initializeDB() method, but if I could get some help I would really appreciate it. Below is the code being used for the intializeDB() method: private void initializeDB() { try { // Load the JDBC driver System.out.println("Driver loaded"); // Establish a connection System.out.println("Database connected"); // Create a statement // Create a SQL Query string // Execute the query to create a recordset } catch (Exception ex) { ex.printStackTrace(); } }

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• Python and database

  - by axl456

  hello.. Am working on a personal project, where i need to manipulate values in a database-like format.. Up until now, am using dictionaries, tuples, and list to store and consult those values. Am thinking about starting to use SQL to manipulate those values, but I dont know if its worth the effort, because I dont know anything about SQL, and I dont want to use something that wont bring me any benefits (if I can do it in a simpler way, i dont want to complicate things) if am only storing and consulting values, what would be the benefit of using SQL? PS: the numbers of row goes between 3 and 100 and the number of columns is around 10 (some may have 5 some may have 10 etc)

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• Help me for creating huge database in Mysql

  - by user90552

  We are building a website for business on global wise, for every country major cities are covered in this concept. I need some suggestions from PHP Mysql People. Can i create single databse for all cities or multiple databases. Because in this system contains some relations between cities ,every chamber need nearly 50 tables for networking and some other tables. If I can create separate databases for every chamber there would be nearly 50*1000 tables need because we have 1000 cities. So Please give suggestions how can i build database for my system. Thank you Ravi

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• Database permissions and ORMs

  - by Jonn

  I've been using .NET's Entity Framework a lot lately and have absolutely no wish to go back to using Stored Procedures. Been shocked though that the company I'm building this project for had a policy where applications were only given accounts that only had permissions to access stored procedures! Apparently, they believe that there's a security risk involved in allowing applications to access the tables/views directly. I don't get this. My first question is, can someone enlighten me as to what kind of security risk applications having direct access to the database may pose? AND If that's the case, are there any other ORM solutions that can provide a workaround to this (I can't think of any logical possibility atm) that would allow me to circumvent the restrictions on the user account to be assigned to me? OR is my understanding that I'd need direct permissions for the tables and views wrong?

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• Database design: How should I add an information which can apply to several tables

  - by Stefan

  I am constructing a database System using Mysql, this will be an application of about 20 tables. The system contains information on farmers, we work with organic certification and need to record a lot of info for that. In my system, there are related parent-child tables for farmers, producing years and fields/areas - it's a simple representation of the real world in which farmers farm crops on their fields. I now need to add several status flags for each one of these levels: a farmer can be certified, or his field can be, or the specific year can be; each of these flags has several states and can occur a number of times. The obvious solution to this would be to add a child table to every one of these tables, and define the states there. What I wonder if there is an easier way to do this to avoid getting to many tables? Where/how would be best practise to keep that data?

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• database row/ record pointers

  - by David

  Hi I don't know the correct words for what I'm trying to find out about and as such having a hard time googling. I want to know whether its possible with databases (technology independent but would be interested to hear whether its possible with Oracle, MySQL and Postgres) to point to specific rows instead of executing my query again. So I might initially execute a query find some rows of interest and then wish to avoid searching for them again by having a list of pointers or some other metadata which indicates the location on a database which I can go to straight away the next time I want those results. I realise there is caching on databases, but I want to keep these "pointers" else where and as such caching doesn't ultimately solve this problem. Is this just an index and I store the index and look up by this? most of my current tables don't have indexes and I don't want the speed decrease that sometimes comes with indexes. So whats the magic term I've been trying to put into google? Cheers

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• Database design for a Fantasy league

  - by Samidh T

  Here's the basic schema for my database Table user{ userid numeber primary key, count number } Table player{ pid number primary key, } Table user-player{ userid number primary key foreign key(user), pid number primary key foreign key(player) } Table temp{ pid number primary key, points number } Here's what I intend to do... After every match the temp table is updated which holds the id of players that played the last match and the points they earned. Next run a procedure that will match the pid from temp table with every uid of user-player table having the same pid. add the points from temp table to the count of user table for every matching uid. empty temp table. My questions is considering 200 players and 10000 users,Will this method be efficient? I am going to be using mysql for this.

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• Database Engine not appearing in SQL Server listing

  - by Jonn

  I don't know if I'm searching for the wrong queries in google but I can't seem to find an answer to this. I have SQL Server 2008 installed in my pc and according to services.msc, I've got 2 database engines running: SQLEXPRESS (probably one that came along with Visual Studio) and MSSQLSERVER. When I try to connect only SQLEXPRESS is visible in the Server Name drop down list. I tried to explicitly state MSSQLSERVER by typing in MYPCNAME\MSSQLSERVER Didn't work. The best solution I could find in the internet was to enable stuff at Configuration Manager. Didn't work either (although I did find that TCP/VIA and all other options were disabled for MSSQLSERVER). Anyone have any other ideas on what I should try next or probably something that I overlooked?

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• Embedded Lua on iPhone. What's new and what does it mean?

  - by John Smith

  Apparently Apple has changed some term in the agreement again. From http://www.appleoutsider.com/2010/06/10/hello-lua/ section 3.3.2 is now Unless otherwise approved by Apple in writing, no interpreted code may be downloaded or used in an Application except for code that is interpreted and run by Apple’s Documented APIs and built-in interpreter(s). Notwithstanding the foregoing, with Apple’s prior written consent, an Application may use embedded interpreted code in a limited way if such use is solely for providing minor features or functionality that are consistent with the intended and advertised purpose of the Application. instead of the original No interpreted code may be downloaded or used in an Application except for code that is interpreted and run by Apple’s Documented APIs and built-in interpreter(s). I am more interested in embedding Lua, but other people have other embeddings they want to make. I am wondering how you ask for permission, and what they mean by the terms "minor features" and "consistent" and how will Apple interpret this section? It seems to have enough loopholes to drive a real firetruck through.

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• Database normalization and duplicate values

  - by bretddog

  Consider a Parent / Child / GrandChild structure in a database table schema, or even a deeper hierarchy. These being in the same aggregate. One table DAYS keeps a single row per day, and has a "Date" field. This is the root table, or maybe a child of the root. No row can ever be deleted in this table. In this case, however complex my table schema looks like, however far away in the hierarchy any other table is, is there any reason why any other table would hold a Date value? Can't it instead just have a FK to the DAYS table. I obviously assume that the creation of these date fields happen not before such datefield exist in the DAYS table. I'm now thinking just about the date part to be relevant, not the time part. Not sure if all databases can store these individually. That's maybe relevant, but not really the focus of the question.

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