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  • Is a 1:* write:read thread system safe?

    - by Di-0xide
    Theoretically, thread-safe code should fix race conditions. Race conditions, as I understand it, occur because two threads attempt to write to the same location at the same time. However, what about a threading model in which a single thread is designed to write to a location, and several slave/worker threads simply read from the location? Assuming the value/timing at which they read the data isn't relevant/doesn't hinder the worker thread's outcome, wouldn't this be considered 'thread safe', or am I missing something in my logic?

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  • Question on different ways to link tables

    - by dotnetdev
    What is the difference between linking two tables and then the PK is an FK in the other table, but the FK has not got the primary key option (so it does not have the gold key), and having the PK in one table as a PK in another table? Am I right to think that the second option is for a many-to-many relationship? Thanks

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  • Complex multiple join query across 3 tables

    - by Keir Simmons
    I have 3 tables: shops, PRIMARY KEY cid,zbid shop_items, PRIMARY KEY id shop_inventory, PRIMARY KEY id shops a is related to shop_items b by the following: a.cid=b.cid AND a.zbid=b.szbid shops is not directly related to shop_inventory shop_items b is related to shop_inventory c by the following: b.cid=c.cid AND b.id=c.iid Now, I would like to run a query which returns a.* (all columns from shops). That would be: SELECT a.* FROM shops a WHERE a.cid=1 AND a.zbid!=0 Note that the WHERE clause is necessary. Next, I want to return the number of items in each shop: SELECT a.*, COUNT(b.id) items FROM shops a LEFT JOIN shop_items b ON b.cid=a.cid AND b.szbid=a.zbid WHERE a.cid=1 GROUP BY b.szbid,b.cid As you can see, I have added a GROUP BY clause for this to work. Next, I want to return the average price of each item in the shop. This isn't too hard: SELECT a.*, COUNT(b.id) items, AVG(COALESCE(b.price,0)) average_price FROM shops a LEFT JOIN shop_items b ON b.cid=a.cid AND b.szbid=a.zbid WHERE a.cid=1 GROUP BY b.szbid,b.cid My next criteria is where it gets complicated. I also want to return the unique buyers for each shop. This can be done by querying shop_inventory c, getting the COUNT(DISTINCT c.zbid). Now remember how these tables are related; this should only be done for the rows in c which relate to an item in b which is owned by the respective shop, a. I tried doing the following: SELECT a.*, COUNT(b.id) items, AVG(COALESCE(b.price,0)) average_price, COUNT(DISTINCT c.zbid) FROM shops a LEFT JOIN shop_items b ON b.cid=a.cid AND b.szbid=a.zbid LEFT JOIN shop_inventory c ON c.cid=b.cid AND c.iid=b.id WHERE a.cid=1 GROUP BY b.szbid,b.cid However, this did not work as it messed up the items value. What is the proper way to achieve this result? I also want to be able to return the total number of purchases made in each shop. This would be done by looking at shop_inventory c and adding up the c.quantity value for each shop. How would I add that in as well?

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  • Secrets of Creating a Digital Marketing System For a Financial Management Firm

    A Financial Management firm can create a strong web presence by designing and developing a business website on the internet. However, this step alone is not a digital marketing plan. Just putting up a Financial Management firm website on the internet is similar to establishing a physical business like a shop or an office, and then just sitting back and waiting for the customers to flow in. More than likely, it will not happen and your website will resemble a billboard in the desert.

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  • sql trigger inserting row into two tables

    - by allen
    I was looking for a way to create a trigger that would insert the same row into two tables with the same values. For example, a new row is inserted into pushNotificationQueue as soon as that is inserted, I would like that same exact row to be inserted into messages. I tried this CREATE TRIGGER add_to_messages after insert on mbb_pushNotificationQueue FOR EACH ROW insert into mbb_messages select * from mbb_pushNotificationQueue the only problem with that is that it goes through and adds entries that have already been previously added.

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  • Pointers to implementing a taxonomy system?

    - by petsagouris
    I am taking part in the development of a PHP CMS (yeah I know you are like, meeh). It is currently using simple tags for tagging content. What I want to do is push the whole thing to using Taxonomy but I am not sure on what to pay attention to, or how to go about structuring the whole vocabularies/terms. I'd love to be able to keep the user interaction close to that of the current simple tags and at the same time allow for more advanced usage by power users. The Drupal and the Wordpress taxonomy systems are being reviewed at the moment and they provide valuable resources. Nevertheless, it could be that someone has some simpler and more appropriate thoughts on this matter.

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  • Why is Wine not installable on my system?

    - by RawX
    So I upgraded on a fresh install to Ubuntu 12.10, not beta, and I've tried installing wine many many times now many different ways but the jist of it is this: This error could be caused by required additional software packages which are missing or not installable. Furthermore there could be a conflict between software packages which are not allowed to be installed at the same time. The following packages have unmet dependencies: wine: Any ideas? It won't let me install the dependencies either it says it needs another set of dependencies to install them -_- im on asus kj50 64bit os dual boot with windows 7 sudo apt-get install wine1.5 Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: wine1.5 : Depends: wine1.5-i386 (= 1.5.15-0ubuntu1) but it is not installable Recommends: gnome-exe-thumbnailer but it is not going to be installed or kde-runtime but it is not going to be installed Recommends: ttf-droid Recommends: ttf-mscorefonts-installer but it is not going to be installed Recommends: ttf-umefont but it is not going to be installed Recommends: ttf-unfonts-core but it is not going to be installed Recommends: winbind but it is not going to be installed Recommends: winetricks but it is not going to be installed E: Unable to correct problems, you have held broken packages.

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  • How to make my proxy settings change depending on the network I connect to?

    - by Little Jawa
    My company's corporate network requires me to set a network proxy to access the net, but when I am anywhere else, I don't need it. The proxy settings in Ubuntu (System - Preferences - Proxy server) allowed me to create "locations" that I can manually select. Then I have a "default" location (with no proxy) and a "work" location (with my company's proxy in it). Is there a way to make Ubuntu automatically select the "work" location based on the connection I'm using? I thought I could use the IP subnet (very specific) to detect where I am, but I have no idea how to set it up... Edit: I really need to have the proxy settings set at the system level. All my network connections (IMAP, SMTP, chat, etc) need to go through the proxy. Not only the web browser.

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  • RPG Equipped Item System

    - by Jimmt
    I'm making a 2d rpg with libgdx and java. I have an Inventory class with an Array of Items, and now I want to be able to equip items onto the player. Would it be more managable to do have every item have an "equipped" boolean flag have an "equipped" array in the player class have individual equipped fields in player class, e.g. private Item equippedWeapon; private Item equippedArmor; public void equipWeapon(Item weapon){ equippedWeapon = weapon; } Or just another way completely? Thanks.

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  • Linux: Configure Xorg X11 Window System

    <b>nixCraft:</b> "My xorg.conf file is missing as I deleted accidentally for some reason. Now, Xorg try to probe my hardware on every startup. How do I configure Xorg under Debian or any Linux distro / operating systems?"

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  • Adding icon to the system tray (notification area)

    - by Moma Antero
    Hello, I have a small audio recording application programmed with GTK/GDK. (see picture). And I would like to add a tray-icon for it so users can control the application window and recording from it. Adding a tray icon: I have planned to use the GtkStatusIcon class for this task. Ref: http://library.gnome.org/devel/gtk/2.11/GtkStatusIcon.html Is GtkStatusIcon the recommended solution that also works in Ubuntu's Unity and in the GNOME 3.0 desktop? I already googled a bit and found a good example on GtkStatusIcon. Could I also use Libindicator for this task? Ref: https://launchpad.net/libindicator

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  • Why not System.Void?

    - by Stewart
    I have no practical reason for knowing this answer, but I'm curious anyway... In C#, trying to use System.Void will produce a compilation error: error CS0673: System.Void cannot be used from C# -- use typeof(void) to get the void type object As I understood it, void is simply an alias of System.Void. So, I don't understand why 'System.Void' can't be used directly as you might with 'string' for 'System.String' for example. I would love to read an explanation for this! Incidentally, System.Void can be successfully used with the Mono compiler, instead of Microsoft's .Net, and there it appears equivalent to using the void keyword. This must therefore be a compiler-enforced restriction rather than a CLR restriction, right?

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  • Hash Tables - Java

    - by Antony
    Am about to do a homework, and i need to store quite a lot of information (Dictionary) in a data structure of my choice. I heard people in my classroom saying hash-tables are the way to go. How come?

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  • How to differenciate two tables

    - by Nemat
    Hi friends.... I have two tables.I want to get all records from one table that are different from the records in second table. For eg. if we have four records in first table like A,B,C,D and three records in second table thats A,B,C then the answer of query should be D. I have tried "EXCEPT" operator but it doesnt work fine.Kindly help me in writing correct query for the given problem. Any help is appreciated.... Thanks in Advance Nemat

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  • GROUP BY and SUM distinct date across 2 tables

    - by kenitech
    I'm not sure if this is possible in one mysql query so I might just combine the results via php. I have 2 tables: 'users' and 'billing' I'm trying to group summed activity for every date that is available in these two tables. 'users' is not historical data but 'billing' contains a record for each transaction. In this example I am showing a user's status which I'd like to sum for created date and deposit amounts that I would also like to sum by created date. I realize there is a bit of a disconnect between the data but I'd like to some all of it together and display it as seen below. This will show me an overview of all of the users by when they were created and what the current statuses are next to total transactions. I've tried UNION as well as LEFT JOIN but I can't seem to get either to work. Union example is pretty close but doesn't combine the dates into one row. ( SELECT created, SUM(status) as totalActive, NULL as totalDeposit FROM users GROUP BY created ) UNION ( SELECT created, NULL as totalActive, SUM(transactionAmount) as totalDeposit FROM billing GROUP BY created ) I've also tried using a date lookup table and joining on the dates but the SUM values are being added multiple times. note: I don't care about the userIds at all but have it in here for the example. users table (where status of '1' denotes "active") (one record for each user) created | userId | status 2010-03-01 | 10 | 0 2010-03-01 | 11 | 1 2010-03-01 | 12 | 1 2010-03-10 | 13 | 0 2010-03-12 | 14 | 1 2010-03-12 | 15 | 1 2010-03-13 | 16 | 0 2010-03-15 | 17 | 1 billing table (record created for every instance of a billing "transaction" created | userId | transactionAmount 2010-03-01 | 10 | 50 2010-03-01 | 18 | 50 2010-03-01 | 19 | 100 2010-03-10 | 89 | 55 2010-03-15 | 16 | 50 2010-03-15 | 12 | 90 2010-03-22 | 99 | 150 desired result: created | sumStatusActive | sumStatusInactive | sumTransactions 2010-03-01 | 2 | 1 | 200 2010-03-10 | 0 | 1 | 55 2010-03-12 | 2 | 0 | 0 2010-03-13 | 0 | 0 | 0 2010-03-15 | 1 | 0 | 140 2010-03-22 | 0 | 0 | 150 Table dump: CREATE TABLE IF NOT EXISTS `users` ( `created` date NOT NULL, `userId` int(11) NOT NULL, `status` smallint(6) NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `users` (`created`, `userId`, `status`) VALUES ('2010-03-01', 10, 0), ('2010-03-01', 11, 1), ('2010-03-01', 12, 1), ('2010-03-10', 13, 0), ('2010-03-12', 14, 1), ('2010-03-12', 15, 1), ('2010-03-13', 16, 0), ('2010-03-15', 17, 1); CREATE TABLE IF NOT EXISTS `billing` ( `created` date NOT NULL, `userId` int(11) NOT NULL, `transactionAmount` int(11) NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `billing` (`created`, `userId`, `transactionAmount`) VALUES ('2010-03-01', 10, 50), ('2010-03-01', 18, 50), ('2010-03-01', 19, 100), ('2010-03-10', 89, 55), ('2010-03-15', 16, 50), ('2010-03-15', 12, 90), ('2010-03-22', 99, 150);

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  • Ubuntu 14.04 Fatal Exception

    - by user286534
    I use Ubuntu 14.04, 64-bit. I installed Virtualbox and was testing another Linux OS (Deepin). My system froze and I could not get to a TTY session to reboot. I had to do a hard restart and when Ubuntu restarted I got various error codes one of which was "kernel panic - fatal exception in interrupt" Booting to Advance mode and attempting repairs did not work (fsck, grub repair, etc) I reinstalled Ubuntu and chose the option to keep my files intact. I can now access my system but many programs I have installed do not work. My question is; I have a Deja-Dup backup (but only of my Home directory), is it better to restore my backup files or do I have to reinstall all of my programs? The weird thing is, the programs I verified using the Software Center to see if they were installed are checked as installed, but won't appear in Dash.

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  • Is System.Windows.Media.RenderCapability the wrong source to detect the current render-mode

    - by happyclicker
    I use System.Windows.Media.RenderCapability.Tier to show the current render mode within a diagnostics panel of my app. If I force the app to change the render-mode through the following code HwndSource hwndSource = PresentationSource.FromVisual(visual) as System.Windows.Interop.HwndSource; HwndTarget hwndTarget = hwndSource.CompositionTarget; hwndTarget.RenderMode = renderMode; neither System.Windows.Media.RenderCapability.TierChanged fires, nor has the System.Windows.Media.RenderCapability.Tier property changed. However the changes are applied to the app. If I look with Perforator, the render mode has been changed to the desired mode. Although I’ve found at many locations that System.Windows.Media.RenderCapability.Tier can be used to detect the current render state (also msdn, see this), it seems, System.Windows.Media.RenderCapability only gives information about the capabilities and not about the current mode. That makes also sense if I look at the name of the class. Is there another source to know how an actual wpf-content is rendered or am I doing something wrong?

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  • SQL Server: compare columns in two tables.

    - by maxt3r
    Hi, I've recently done a migration from a really old version of some application to the current version and i faced some problems while migrating databases. I need a query that could help me to compare columns in two tables. I mean not the data in rows, I need to compare the columns itself to figure out, what changes in table structure I've missed.

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  • Implementing cache system in Java Web Application

    - by TGM
    I worked with JPA (Eclipselink implementation) and Hibernate. As I understand these two have great caching systems. I am interested in caching in a Web application and in order to better understand the process I'm trying to implement something on my own. Sadly, I cannot find any in depth documentation about this subject. I'm interested in things like high scalability, sharing memory on different machines and other important theoretical matters. Is there any tutorial or open project I could check out? Thank you! *LE: * I want to cache DB information in POJOs just like JPA or Eclipselink

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  • Cannot upgrade system because of this error

    - by user292375
    Setting up mongodb-org-server (2.6.1) ... * Starting database mongod [fail] invoke-rc.d: initscript mongod, action "start" failed. dpkg: error processing mongodb-org-server (--configure): subprocess installed post-installation script returned error exit status 1 No apport report written because MaxReports is reached already dpkg: dependency problems prevent configuration of mongodb-org: mongodb-org depends on mongodb-org-server; however: Package mongodb-org-server is not configured yet. dpkg: error processing mongodb-org (--configure): dependency problems - leaving unconfigured No apport report written because MaxReports is reached already Errors were encountered while processing: mongodb-org-server mongodb-org E: Sub-process /usr/bin/dpkg returned an error code (1)

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  • the new distro ubuntu 12.10 has 2 system Bugs, reinstall the iso also exist [closed]

    - by sunpoison
    Possible Duplicate: How do I report a bug? discovered 2 bugs:: 1)cannot restart the computer when you click the top right icon power key "restart", it will stay on the splash image "ubuntu...",i wait for about 7 minutes and more, it also cannot restart, so, i have to uninstall the battery of the laptop...... 2)when i first update to the 12.10,not run for few hours, the "input method icon" on the top state bar is suddenly hide, when i use the shortcuts to switch the input method with "ctrl +space" it doesn' work at all, i restart the laptop, it can change the input method, but the state icon "a small keyboard icon is escape, i goto the "i bus" settings, but when i how to adjust it, the icon still can't display on the top bar (now i reinstall it use the iso file, this bug is fixed, but it cannot restart like the former one) it must has some problems of the "i bus" input method

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  • MySQL Joining three tables

    - by text
    I am doing a query with three tables, the problem was one table has many occurrences of id of another. sample data: users: id answers: id:1 user_answer :1 id:1 user_answer :2 id:1 user_answer :3 Questions: id:1 answers :answer description id:2 answers :answer description id:3 answers :answer description How can I get all user information and all answer and its description, I used GROUP by user.id but it only returns only one answer. I want to return something like this list all of users answer: Name Q1 Q2 USERNAME ans1,ans2 ans1,ans2 comma separated description of answer here

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