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  • Splitting tables by field to optimize MySQL?

    - by AK
    Do splitting fields into multiple tables ever yield faster queries? Consider the following two scenarios: Table1 ----------- int PersonID text Value1 float Value2 or Table1 ----------- int PersonID text Value1 Table2 ----------- int PersonID float Value2 If Value1 and Value2 are always being displayed together, I imagine Table1 is always faster because the second schema would require two SELECT statements. But are there any situations where you would choose the second? If the number of records were expected to be really large?

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  • MultiOS "Jet Database" for C++/Qt?

    - by Airjoe
    Hopefully I can articulate this well: I'm porting an application I made years ago from VB6 (I know, I know!) to C++/Qt. 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 Qt 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 do I get the CPU speed and total physical ram in C#?

    - by edude05
    I need a simple way of checking how much ram and fast the CPU of the host PC is. I tried WMI however the code I'm using private long getCPU() { ManagementClass mObject = new ManagementClass("Win32_Processor"); mObject.Get(); return (long)mObject.Properties["MaxClockSpeed"].Value; } Throws a null reference exception. Furthermore, WMI queries are a bit slow and I need to make a few to get all the specs. Is there a better way?

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  • Need some sort of "conditional grouping" in MySQL.

    - by serg555
    I have Article table: id | type | date ----------------------- 1 | A | 2010-01-01 2 | A | 2010-01-01 3 | B | 2010-01-01 Field type can be A, B or C. I need to run a report that would return how many articles of each type there is per every day, like this: date | count(type="A") | count(type="B") | count(type="C") ----------------------------------------------------- 2010-01-01 | 2 | 1 | 0 2010-01-02 | 5 | 6 | 7 Currently I am running 3 queries for every type and then manually merging the results select date, count(id) from article where type="A" group by date Is it possible to do this in one query? (in pure sql, no stored procedures or anything like that). Thanks

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  • HTML Encoding with ASP.NET

    - by Corin
    I am currently html encoding all user entered text before inserting/updating a db table record. The problem is that on any subsequent updates, the previously encoded string is reencoded. This endless loop is starting to eat up alot of column space in my tables. I am using parameterized queries for all sql statements but am wondering would it be safe to just let the .NET Framework handle this part without the HTML Encoding?

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  • Get size of max possible result set

    - by wheresrhys
    For my application most of my SQL queries return a specified number of rows. I'd also like to get the maximum possible number of results i.e. how many rows would be returned if I wasn't setting a LIMIT. Is there a more efficient way to do this (using just SQL?) than returning all the results, getting the size of the result set and then splicing the set to return just the first N rows.

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  • How significant are JPA lazy loading performance benefits?

    - by Robert
    I understand that this is highly specific to the concrete application, but I'm just wondering what's the general opinion, or at least some personal experiences on the issue. I have an aversion towards the 'open session in view' pattern, so to avoid it, I'm thinking about simply fetching everything small eagerly, and using queries in the service layer to fetch larger stuff. Has anyone used this and regretted it? And is there maybe some elegant solution to lazy loading in the view layer that I'm not aware of?

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  • Best practices for implementing an Access (2007) application

    - by waanders
    Hello, Where can I find an overview (website) of best practices for implementing an Access (2007) application (with a FE/BE architecture) regarding to security, performance and maintainability? I know about designing tables, queries, forms and so on and I'm a reasonable programmer, but I'm wondering what's the "best" and most efficient way to implement my "application". Thanks in advance for your help.

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  • Java: Cannot listen to port, BindException

    - by bguiz
    Hi, I am developing an application in Netbeans, and it is using JavaDB. I can connect to it and execute queries without issues, but for some reason, the "Output - JavaDB Database Process" pane within Netbeans keeps displaying Security manager installed using the Basic server security policy. Could not listen on port 1527 on host localhost: java.net.BindException: Address already in use How do I find out what process is already using, or bound to, that port number?

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  • how to store a value returned from a sql query in a variable in batch programming ?

    - by Arunachalam
    how to store a value returned from a sql query in a variable in batch programming ? i can invoke sqlserver queries from my cmd prompt using sqlcmd server name then the qwery this is query statement i m going to use SELECT CASE WHEN DATEDIFF(minute, record_timestamp, GETDATE()) < 10 THEN 1 ELSE 0 END how to store the value returned i tried using set variablename but it save the statement rather than the return value .. and if i save this in a variable what type of variable it will can i compare it with numeric values in if condition

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  • nhibernate intercept select query

    - by mjmcloug
    Hey, I'm looking at the nhibernate interceptor. It seems to be able to intercept save, update and delete queries but is there anyway I can intercept a select query. The problem I have is that I automatically want to append some additional sql filters to the executing sql statement in certain cases. Any thoughts Thanks Mat

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  • PostgreSQL: Why does this simple query not use the index?

    - by David
    I have a table t with a column c, which is an int and has a btree index on it. Why does the following query not utilize this index? explain select c from t group by c; The result I get is: HashAggregate (cost=1005817.55..1005817.71 rows=16 width=4) -> Seq Scan on t (cost=0.00..946059.84 rows=23903084 width=4) My understanding of indexes is limited, but I thought such queries were the purpose of indexes.

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  • How to salvage SQL server 2008 query from KILLED/ROLLBACK state without waiting half a day?

    - by littlegreen
    I have a stored procedure that inserts batches of millions of rows, emerging from a certain query, into an SQL database. It has one parameter selecting the batch; when this parameter is omitted, it will gather a list of batches and recursively call itself, in order to iterate over batches. In (pseudo-)code, it looks something like this: CREATE PROCEDURE spProcedure AS BEGIN IF @code = 0 BEGIN ... WHILE @@Fetch_Status=0 BEGIN EXEC spProcedure @code FETCH NEXT ... INTO @code END END ELSE BEGIN -- Disable indexes ... INSERT INTO table SELECT (...) -- Enable indexes ... Now it can happen that this procedure is slow, for whatever reason: it can't get a lock, one of the indexes it uses is misdefined or disabled. In that case, I want to be able kill the procedure, truncate and recreate the resulting table, and try again. However, when I try and kill the procedure, the process frequently oozes into a KILLED/ROLLBACK state from which there seems to be no return. From Google I have learned to do an sp_lock, find the spid, and then kill it with KILL <spid>. But when I try to kill it, it tells me SPID 75: transaction rollback in progress. Estimated rollback completion: 0%. Estimated time remaining: 554 seconds. I did find a forum message hinting that another spid should be killed before the other one can start a rollback. But that didn't work for me either, plus I do not understand, why that would be the case... could it be because I am recursively calling my own stored procedure? (But it should be having the same spid, right?) In any case, my process is just sitting there, being dead, not responding to kills, and locking the table. This is very frustrating, as I want to go on developing my queries, not waiting hours on my server sitting dead while pretending to be finishing a supposed rollback. Is there some way in which I can tell the server not to store any rollback information for my query? Or not to allow any other queries to interfere with the rollback, so that it will not take so long? Or how to rewrite my query in a better way, or how kill the process successfully without restarting the server?

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  • Using a single xcode proj for iphone and ipad- can I use same push notification certificate ?

    - by Shweta
    Hi I am looking for extending my current iphone app for iPad-specific UI. For the same Apple has mentioned 3 ways, however I am using the method where a Single XCODE proj is used for having 2 targets- iphone & iPad. There are a few queries: two binaries will be created , which I can price differently for selling. Will they need 2 have different certificates from Apple ? My app has Push notifications. So will i require 2 different certificates ?

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  • amzi prolog + eclipse question

    - by alan
    hey guys i have a question regarding amzi prolog with eclipse, Im running a .pro file which executes a breadth first search and if queue gets too long, the following error message appears: system_error 1021 Control stack full. Compile code or increase .cfg parameter 'control' If so, how may i run the compiled code under eclipse? I've tried running the project but the listener just ends without accepting any queries....?

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  • SQLite - ON DUPLICATE KEY UPDATE

    - by Alix Axel
    MySQL has something like this: INSERT INTO visits (ip, hits) VALUES ('127.0.0.1', 1) ON DUPLICATE KEY UPDATE hits = hits + 1; As far as I'm know this feature doesn't exist in SQLite, what I want to know is if there is any way to archive the same effect without having to execute two queries. Also, if this is not possible, what do you prefer: SELECT + (INSERT or UPDATE) or UPDATE (+ INSERT if UPDATE fails)

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  • How to avoid fast rate page refresh in ASP.NET ?

    - by eugeneK
    I have a page that shows statistics for users, this cannot be cached because each user has different statistics and there are many thus the real time query must be made. What the way to avoid database server overload when user will click F5's to refresh or to ask different queries in short time intervals ?

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  • MYSQL JOIN SELECT Statment - omit duplicated

    - by mouthpiec
    Hi, I am tying to join the following 2 queries but I am having duplicated .... it is possible to remove duplacted fro this: ( SELECT bar_id, bar_name, town_name, bar_telephone, (subscription_type_id *2) AS subscription_type_id FROM bar, sportactivitybar, towns, subscriptiontype WHERE sport_activity_id_fk =14 AND bar_id = bar_id_fk AND town_id = town_id_fk AND subscription_type_id = subscription_type_id_fk ) UNION ( SELECT bar_id, bar_name, town_name, bar_telephone, subscription_type_id FROM bar, towns, subscriptiontype WHERE town_id = town_id_fk AND subscription_type_id = subscription_type_id_fk ) ORDER BY subscription_type_id DESC , RAND( ) Please note that I need to omit those duplicates that will have a lower subscription_type_id

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  • NHibernate LINQ + PLINQ

    - by cvista
    Hi i've just started reading up on PLINQ and find it fasinating. I'm using NHib-Linq in my projects - does anyone know if there's any benefit/problems using PLINQ type queries with NHLinq? w://

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  • Is there a way to get photo tags and new friendship type events by querying the FQL stream table?

    - by Fletcher Moore
    When you look at your stream on the Facebook website, events such as "FriendX was tagged in an album", "FriendY is attending EventZ", and "FriendK and FriendL are now friends". I've tried various "vague" queries on the stream table, and so far I have been unable to get these types of events. Is this possible, or do I need to query the all of the other tables and write a ton of logic to try to figure out which new events to show and how to show them?

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  • Loading the last related record instantly for multiple parent records using Entity framework

    - by Guillaume Schuermans
    Does anyone know a good approach using Entity Framework for the problem described below? I am trying for our next release to come up with a performant way to show the placed orders for the logged on customer. Of course paging is always a good technique to use when a lot of data is available I would like to see an answer without any paging techniques. Here's the story: a customer places an order which gets an orderstatus = PENDING. Depending on some strategy we move that order up the chain in order to get it APPROVED. Every change of status is logged so we can see a trace for statusses and maybe even an extra line of comment per status which can provide some extra valuable information to whoever sees this order in an interface. So an Order is linked to a Customer. One order can have multiple orderstatusses stored in OrderStatusHistory. In my testscenario I am using a customer which has 100+ Orders each with about 5 records in the OrderStatusHistory-table. I would for now like to see all orders in one page not using paging where for each Order I show the last relevant Status and the extra comment (if there is any for this last status; both fields coming from OrderStatusHistory; the record with the highest Id for the given OrderId). There are multiple scenarios I have tried, but I would like to see any potential other solutions or comments on the things I have already tried. Trying to do Include() when getting Orders but this still results in multiple queries launched on the database. Each order triggers an extra query to the database to get all orderstatusses in the history table. So all statusses are queried here instead of just returning the last relevant one, plus 100 extra queries are launched for 100 orders. You can imagine the problem when there are 100000+ orders in the database. Having 2 computed columns on the database: LastStatus, LastStatusInformation and a regular Linq-Query which gets those columns which are available through the Entity-model. The problem with this approach is the fact that those computed columns are determined using a scalar function which can not be changed without removing the formula from the computed column, etc... In the end I am very familiar with SQL and Stored procedures, but since the rest of the data-layer uses Entity Framework I would like to stick to it as long as possible, even though I have my doubts about performance. Using the SQL approach I would write something like this: WITH cte (RN, OrderId, [Status], Information) AS ( SELECT ROW_NUMBER() OVER (PARTITION BY OrderId ORDER BY Id DESC), OrderId, [Status], Information FROM OrderStatus ) SELECT o.Id, cte.[Status], cte.Information AS StatusInformation, o.* FROM [Order] o INNER JOIN cte ON o.Id = cte.OrderId AND cte.RN = 1 WHERE CustomerId = @CustomerId ORDER BY 1 DESC; which returns all orders for the customer with the statusinformation provided by the Common Table Expression. Does anyone know a good approach using Entity Framework?

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  • Creating a Web Service to automatically get information

    - by Sean P
    I want to create some sort of method of creating a web service that will run automatically and run DB queries and some API calls which will then store data that I can use/call without taking the processing or time penalty of doing it every time a user access my web service. Is this possible? If so, point me in the right direction on how to implement something like this Using vb.net and ASP.net Thanks in advance!!

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