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  • MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

    - by Cory House
    MySQL doesn't currently support updating rows in the same table the trigger is assigned to since the call could become recursive. Does anyone have suggestions on a good workaround/alternative? Right now my plan is to call a stored procedure that performs the logic I really wanted in a trigger, but I'd love to hear how others have gotten around this limitation. Edit: A little more background as requested. I have a table that stores product attribute assignments. When a new parent product record is inserted, I'd like the trigger to perform a corresponding insert in the same table for each child record. This denormalization is necessary for performance. MySQL doesn't support this and throws: Can't update table 'mytable' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. A long discussion on the issue on the MySQL forums basically lead to: Use a stored proc, which is what I went with for now. Thanks in advance!

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  • How to store data in mysql, to get the fastest performance?

    - by Oden
    Hey, I'm thinking about it, witch of the following two query types would give me the fastest performance for a user messaging module inside my site: The first one i thought about is a multi table setup, witch has a connection table, and a main table. The connection table holds the connection between accounts, and the messaging table. In this case a query would look like following, to get some data of the author, and the messages he has sent: SELECT m.*, a.username FROM messages AS m LEFT JOIN connection_table ON (message_id = m.id) LEFT JOIN accounts AS a ON (account_id = a.id) WHERE m.id = '32341' Inserting into it is a little bit more "complicated". My other idea, and in my thought the better solution of this problem is that i store the data i would use in a connection table in the same table where is store the data of the mail. Sounds like i would get lots of duplicated entries, but no, because i have a field witch has text type and holds user ids like this: *24*32*249* If I want to query them, i use the mysql LIKE method. Deleting is an other problem, but for this i have one more field where i store who has deleted the post. Sad about that i don't know how to join this. So what would you recommend? Are there other ways?

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  • Local sites not displaying in VirtualBox when using Django's local development server?

    - by littlejim84
    Hello. I develop web applications using Django on Mac OSX 10.6. I use Django's built in local development server which I run on my computer's IP (such as: http://192.168.0.11:8001/). I test my applications in Firefox, Safari and Chrome and all display fine. I use Sun's VirtualBox with 3 different instances of Windows XP that have IE6, IE7 and IE8 on them. For whatever reason, these sometimes just don't display the Django sites. They come up with 'The page cannot be displayed'. Eight times out of ten, they display fine and function normally but for no reason at all they won't display. Sometimes restarting Django's local development server from the Terminal will fix the problem, sometimes it won't. Is there some sort of VirtualBox settings or Django settings that I need to set to ensure smooth operation of this? Am I overlooking something? Has anyone else had these problems?

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  • What is the best schema design for child collection with a "primary" entity

    - by erg39
    Here is the scenario: You have a Persons table with a one-to-many relationship with an Addresses table, where one of the Address rows is the "primary" Address. Is it better in a normalized schema to Use a Persons.PrimaryAddressID to access the "primary" Address for a Person or Use an Addresses.IsPrimary bit column to reference the "primary" Address for a Person via Addresses.PersonID or Other and why?

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  • How do I create a free server-side database to be accessed via Windows forms and/or browser?

    - by NoCatharsis
    I have no formal education in databasing or programming, but I've learned enough SQL, C++, and C# to at least get started setting up a small database on my company's server. Using MS SQL Server 2008 R2, I have created the database and set up columns with proper data types. However, there seems to be a lot of tweaks and details that are way over my head. Since I would like these data to be accessible to the other 7 or 8 people in my office (preferably via web browser), I'm wondering whether this is the best setup for my situation. The other option I've read about is a LAMPP server, which I assume is the competing free option to Microsoft's Express packages. I know nothing of LAMP servers except from the articles I've read on how to set them up (and I believe I even saw a detailed tutorial somewhere). To summarize, my question is this: Which of these (or any other) server setups would best suit my purposes, keeping in mind that I'm a true novice (but willing to learn), and would like to keep it free until I get more experience?

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  • InnoDB or MyISAM - Why not both?

    - by Skoder
    Hey. I'm new to databases, and I've read various threads about which is better between InnoDB and MyISAM. It seems that the debates are to use or the other. Is it not possible to use both, depending on the table? What would be the disadvantages in doing this? As far as I can tell, the engine can be set during the CREATE TABLE command. Therefore, certain tables which are often read can be set to MyISAM, but tables that need transaction support can use InnoDB. I'm sure there must be a problem, otherwise this would be the ultimate answer :).

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  • Most valued skill set in web development industry/what should I be doing now? (Kinda random "career"

    - by Andrew
    I want to be a web programmer [when I grow up?] because it's what I like doing, and I really do thoroughly enjoy it (web development in general, actually). I have about 2 years experience with PHP, CSS, and HTML and a few months experiance with JS and jQuery. I've been wondering this for a while -- what languages should I be most familiar with if I want to try and make a career out of web development? I'm only 17, so I've got plenty of time, and I think I've got a decent headstart on things, but it doesn't hurt to ask. If I'm thinking in terms of being able to get hired as a web programmer, what is (or what are...?) the most useful thing I can do now to be able to have an upper hand when it comes to looking for a job. What languages, as a young programmer, should I really focus on? If you were looking to hire a developer, what would you be looking for?

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  • Is it possible to listen to relational database update?

    - by Morgan Cheng
    Is it possible to listen to relation database update? For example, my web app want to send data update to client through Comet technology. I can have the program to poll the database periodically, but that would not be performant and scalable. If app can hood to a "event handler" of database, then app can get notification every time given database table data is updated. This sounds more promising, but I didn't find any concrete example for it. This is listener pattern. Does common relational database support such feature?

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  • Relational MySQL - fetched properties?

    - by Kelso.b
    I'm currently using the following PHP code: // Get all subordinates $subords = array(); $supervisorID = $this->session->userdata('supervisor_id'); $result = $this->db->query(sprintf("SELECT * FROM users WHERE supervisor_id=%d AND id!=%d",$supervisorID, $supervisorID)); $user_list_query = 'user_id='.$supervisorID; foreach($result->result() as $user){ $user_list_query .= ' OR user_id='.$user->id; $subords[$user->id] = $user; } // Get Submissions $submissionsResult = $this->db->query(sprintf("SELECT * FROM submissions WHERE %s", $user_list_query)); $submissions = array(); foreach($submissionsResult->result() as $submission){ $entriesResult = $this->db->query(sprintf("SELECT * FROM submittedentries WHERE timestamp=%d", $submission->timestamp)); $entries = array(); foreach($entriesResult->result() as $entries) $entries[] = $entry; $submissions[] = array( 'user' => $subords[$submission->user_id], 'entries' => $entries ); $entriesResult->free_result(); } Basically I'm getting a list of users that are subordinates of a given supervisor_id (every user entry has a supervisor_id field), then grabbing entries belonging to any of those users. I can't help but think there is a more elegant way of doing this, like SELECT FROM tablename where user->supervisor_id=2222 Is there something like this with PHP/MySQL? Should probably learn relational databases properly sometime. :(

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  • What are some useful SQL statements that should be known by all developers who may touch the Back en

    - by Jian Lin
    What are some useful SQL statements that should be known by all developers who may touch the Back end side of the project? (Update: just like in algorithm, we know there are sorting problems, shuffling problems, and we know some solutions to them. This question is aiming at the same thing). For example, ones I can think of are: Get a list of Employees and their boss. Or one with the employee's salary greater than the boss. (Self-join) Get a list of the most popular Classes registered by students, from the greatest number to the smallest. (Count, group by, order by) Get a list of Classes that are not registered by any students. (Outer join and check whether the match is NULL, or by Get from Classes table, all ClassIDs which are NOT IN (a subquery to get all ClassIDs from the Registrations table)) Are there some SQL statements that should be under the sleeve of all developers that might touch back end data?

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  • Whats the best solution for a database used in conjunction with Maps in Android?

    - by Andrew
    Could someone please point me in the right direction. My project involves a database where users enter their address and other info from my website. This database is then referenced in my android application to show the locations of these addresses in my database. I have yet to start and just came up with this idea. My question is, what would be the best method to create a database easily modified through my website (mySQL, php, etc), and also easily referenced easily through Android and the Google Maps API? I need some ideas on the languages I will need to use to create this database and website so I can go buy the necessary books to start reading up. Thanks so much

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  • How do you store sets in Cassandra?

    - by Ben W
    I'd like to convert this JSON to a data model in Cassandra, where each of the arrays is a set with no duplicates: var data = { "data1": { "100": [1, 2, 3], "200": [3, 4] }, "data2": { "k1", [1], "k2", [4, 5] } } I'd like to query like this: data["data1"]["100"] to retrieve the sets. Anyone know how you might model this in Cassandra? (The only thing I came up with was columns whose name was a set value and the value of the column was an empty string, but that felt wrong.) It's not OK to serialize the sets as JSON or some other string, which would make this much easier. Also, I should note that it's OK to split data1 and data2 into separate ColumnFamilies, it's not necessary that they're keys in the same one.

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  • Using "CASE" in Where clause to choose various column harm the performance

    - by zivgabo
    I have query which needs to be dynamic on some of the columns, meaning I get a parameter and according its value I decide which column to fetch in my Where clause. I've implemented this request using "CASE" expression: (CASE @isArrivalTime WHEN 1 THEN ArrivalTime ELSE PickedupTime END) >= DATEADD(mi, -@TZOffsetInMins, @sTime) AND (CASE @isArrivalTime WHEN 1 THEN ArrivalTime ELSE PickedupTime END) < DATEADD(mi, -@TZOffsetInMins, @fTime) If @isArrivalTime = 1 then chose ArrivalTime column else chose PickedupTime column. I have a clustered index on ArrivalTime and nonclustered index on PickedupTime. I've noticed that when I'm using this query (with @isArrivalTime = 1), my performance is a lot worse comparing to only using ArrivalTime. Maybe the query optimizer can't use\choose the index properly in this way? I compared the execution plans an noticed that when I'm using the CASE 32% of the time is being wasted on the index scan, but when I didn't use the CASE(just usedArrivalTime`) only 3% were wasted on this index scan. Anyone know the reason for this?

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  • Is there any small linux distribution which comes with a complete C development environment

    - by hits_lucky
    Hi, I have installed "Damn Small Linux" on my home computer for doing C development in unix. But the distribution doesn't by default come with the C development environment and I am facing some issues when trying to install the gcc. Is there any other small Linux distribution which by default has the required packages for the C development. And also I don't want additional software which takes up lot of space but still would like to have the graphical environment. Thanks

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  • Are you using Virtual Machine as your primary development enviroment?

    - by Click Ok
    Recently I have purchased a notebook that cames with Windows Home Basic (that don't have with ASP.Net/IIS. I thought in upgrade the Windows version to one with ASP.Net/IIS, but I thought in another possibility: I have an Hard Disk Case with a 360Gb HD. I thought in create a virtual machine with Windows Ultimate (installing too ASP.Net, IIS and Visual Studio 2008) in this HD Case, then I can access my "development enviroment" in any computer that I will work on (my desktop machine and my notebook). But I was worried about the performance. I don't have experience working in Virtual Machines (I use it just to quick compatibility tests)... Are you using Virtual Machine as your primary development enviroment? What your finds? ==================== Thanks for your answers! It really did help me! I would like to know too about portability ie.: the virtual machine that I created in my laptop will work in the desktop? I will need re-activate Windows?

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  • which is better, creating a materialized view or a new table?

    - by Carson
    I have some demanding mysql queries that are needed to grap same up-to-date datasets from 5-7 mysql tables. I am thinking of creating a table or materialized view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create materialized view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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  • How to use Unique Composite Key

    - by LifeH2O
    I have a table Item(ItemName*, ItemSize*, Price, Notes) I was making composite key of (ItemName,ItemSize) to uniquely identify item. And now after reading some answers on stackoverflow suggesting the use of UNIQUE i revised it as Item(ItemID*, ItemName, ItemSize, Price, Notes) But How to apply UNIQUE constraint on ItemName and ItemSize please correct if there is something wrong in question

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  • DB Design to store custom fields for a table

    - by Fazal
    Hi All, this question came up based on the responses I got for the question http://stackoverflow.com/questions/2785033/getting-wierd-issue-with-to-number-function-in-oracle As everyone suggested that storing Numeric values in VARCHAR2 columns is not a good practice (which I totally agree with), I am wondering about a basic Design choice our team has made and whether there are better way to design. Problem Statement : We Have many tables where we want to give certain number of custom fields. The number of required custom fields is known, but what kind of attribute is mapped to the column is available to the user E.g. I am putting down a hypothetical scenario below Say you have a laptop which stores 50 attribute values for every laptop record. Each laptop attributes are created by the some admin who creates the laptop. A user created a laptop product lets say lap1 with attributes String, String, numeric, numeric, String Second user created laptop lap2 with attributes String,numeric,String,String,numeric Currently there data in our design gets persisted as following Laptop Table Id Name field1 field2 field3 field4 field5 1 lap1 lappy lappy 12 13 lappy 2 lap2 lappy2 13 lappy2 lapp2 12 This example kind of simulates our requirement and our design Now here if somebody is lookinup records for lap2 table doing a comparison on field2, We need to apply TO_NUMBER. select * from laptop where name='lap2' and TO_NUMBER(field2) < 15 TO_NUMBER fails in some cases when query plan decides to first apply to_number instead of the other filter. QUESTION Is this a valid design? What are the other alternative ways to solve this problem One of our team mates suggested creating tables on the fly for such cases. Is that a good idea How do popular ORM tools give custom fields or flex fields handling? I hope I was able to make sense in the question. Sorry for such a long text.. This causes us to use TO_NUMBER when queryio

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  • What are some useful SQL statements / usage patterns that should be known by all developers who may

    - by Jian Lin
    What are some useful SQL statements that should be known by all developers who may touch the Back end side of the project? (Update: just like in algorithm, we know there are sorting problems, shuffling problems, and we know some solutions to them. This question is aiming at the same thing). For example, ones I can think of are: Get a list of Employees and their boss. Or one with the employee's salary greater than the boss. (Self-join) Get a list of the most popular Classes registered by students, from the greatest number to the smallest. (Count, group by, order by) Get a list of Classes that are not registered by any students. (Outer join and check whether the match is NULL, or by Get from Classes table, all ClassIDs which are NOT IN (a subquery to get all ClassIDs from the Registrations table)) Are there some SQL statements that should be under the sleeve of all developers that might touch back end data?

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  • Facebook Api - Local development, Testserver, Liveserver ... How?

    - by Thijs Kaspers
    I'm working on a new website that uses the Facebook API for users to login and several implementations of the graph Api. My workflow usually is: Development on localhost Development using MAMP/XAMPP or similar software Push to server - testing domain A team of people can test the changes for a few days to see if everything works as planned. Push to server - live domain Changes are live for public Facebook uses the site URL in the appsettings and for security reasons, they will only redirect to that url... Problem is.. I have localhost and 2 different domains. How can I make this work? Ofcourse I could edit the hostsfile, but that only fixes it for localhost.. Still no solution for the testdomain. Please tell me this is somehow possible! I'm getting more and more depressed with the Facebook API.

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  • My database has been deleted suddenly on the server how to recover it?

    - by user2728312
    I'm running an application on windows server that connect to a SQL Server database. Today, when I opened SQL Server Management Studio, I was surprised the database is not in the list of the databases! I don't know what's the reason. I searched in the server files but I can't find the database and also in the recycle bin. I put my database in C:\db\myWeb.mdf and suddenly it's been removed! Can anyone tell me how to recover the database?

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  • Error(2,7): PLS-00428: an INTO clause is expected in this SELECT statement

    - by omgzor
    I'm trying to create this trigger and getting the following compiler errors: create or replace TRIGGER RESTAR_PLAZAS AFTER INSERT ON PLAN_VUELO BEGIN SELECT F.NRO_VUELO, M.CAPACIDAD, M.CAPACIDAD - COALESCE(( SELECT count(*) FROM PLAN_VUELO P WHERE P.NRO_VUELO = F.NRO_VUELO ), 0) as PLAZAS_DISPONIBLES FROM VUELO F INNER JOIN MODELO M ON M.ID = F.CODIGO_AVION; END RESTAR_PLAZAS; Error(2,7): PL/SQL: SQL Statement ignored Error(8,5): PL/SQL: ORA-00933: SQL command not properly ended Error(8,27): PLS-00103: Encountered the symbol "end-of-file" when expecting one of the following: begin case declare end exception exit for goto if loop mod null pragma raise return select update while with <an identifier> <a double-quoted delimited-identifier> <a bind variable> << close current delete fetch lock insert open rollback savepoint set sql execute commit forall merge pipe Error(2,1): PLS-00428: an INTO clause is expected in this SELECT statement What's wrong with this trigger?

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