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  • What's the proper way to use sqlite on the iPhone?

    - by Elliot Chen
    Hi, Experts: Can you please give some suggestions on sqlite using on the iPhone? Within my application, I use a sqlite DB to store all local data. Two methods can be used to retrieve those data during running time. 1, Load all the data into memory at initialization stage. (More memory used, less DB open/close operation needed) 2, Read corresponding records when necessary, free the occupied memory after using. (Good habit for memory using, but much DB open/close operations needs). I prefer to use method 2, but not sure whether too many DB opening/closing operations could affect app's efficiency. Or do you think I can 'upgrade' method 2 by opening DB when app launches and closing DB when app quits? Thanks for your suggestions very much!

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  • Whats the significance of creating three db's in ruby and rails.

    - by piemesons
    Hello friends i am moving from php to ruby on rails. Suppose u want to create a application in ruby on rails rails depot -d mysql This will create a application depot with database mysql right..!!! Now config/database.yml has a definition of three databases ie depot_development, depot_test and depot_production under environment development , test and production respectiviely Whats the significance of creating these three databases.. (Please explain considering this is my first day with ruby on rails and i am takin help from Agile Web Development with Rails)

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  • Letting users try your web app before sign-up: sessions or temp db?

    - by Mat
    I've seen a few instances now where web applications are letting try them out without you having to sign-up (though to save you need to of course). example: try at http://minutedock.com/ I'm wondering about doing this for my own web app and the fundamental question is whether to store their info into sessions or into a temp user table? The temp user table would allow logging and potentially be less of a hit on the server, correct? Is there a best practice here?

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  • how do i load an image from a DB inside a jsf using managed beans?

    - by RhigoHR
    Hi.. i have a database with some images...could anyone tell me or explain me how could i can load an image in a jsf? I alredy have a managed bean that converts an Image object into a streamcontent...and this streamcontent is called from the page in a tag , but when a i check the source code of the page, there's no src where the image could be loaded. Hope an answer, thx

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  • Is it ok to perform DB operation on UI thread?

    - by user648462
    I am using a database to persist the state of a search form. I am using the onPause method to persist the data and the onResume method to restore it. My opinion is that restoring and persisting state should be a blocking operation so I plan to perform the database operations on the UI thread. I know this is generally discouraged but the operations should be quick and I think if they were done asynchronously they could lead to inconsistent UI behaviour. Any advice

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  • Cannot add an entity that already exists. (LINQ to SQL)

    - by Vicheanak
    Hello guys, in my database there are 3 tables CustomerType CusID EventType EventTypeID CustomerEventType CusID EventTypeID Dim db = new CustomerEventDataContext Dim newEvent = new EventType newEvent.EventTypeID = txtEventID.text db.EventType.InsertOnSubmit(newEvent) db.SubmitChanges() 'To select the last ID of event' Dim lastEventID = (from e in db.EventType Select e.EventTypeID Order By EventTypeID Descending).first() Dim chkbx As CheckBoxList = CType(form1.FindControl("CheckBoxList1"), CheckBoxList) Dim newCustomerEventType = New CustomerEventType Dim i As Integer For i = 0 To chkbx.Items.Count - 1 Step i + 1 If (chkbx.Items(i).Selected) Then newCustomerEventType.INTEVENTTYPEID = lastEventID newCustomerEventType.INTSTUDENTTYPEID = chkbxStudentType.Items(i).Value db.CustomerEventType.InsertOnSubmit(newCustomerEventType) db.SubmitChanges() End If Next It works fine when I checked only 1 Single ID of CustomerEventType from CheckBoxList1. It inserts data into EventType with ID 1 and CustomerEventType ID 1. However, when I checked both of them, the error message said Cannot add an entity that already exists. Any suggestions please? Thx in advance.

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  • need help with db-query on sql-server 2005.

    - by Avinash
    We're seeing strange behavior when running two versions of a query on SQL Server 2005: version A: SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = 1234 ORDER BY name ASC version B: DECLARE @Id AS INT; SET @Id = 1234; SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = @Id ORDER BY name ASC Both queries return 1000 rows; version A takes on average 15s; version B on average takes 4s. Could anyone help us understand the difference in execution times of these two versions of SQL? If we invoke this query via named parameters using NHibernate, we see the following query via SQL Server profiler: EXEC sp_executesql N'SELECT otherattributes.* FROM listcontacts JOIN otherattributes ON listcontacts.contactId = otherattributes.contactId WHERE listcontacts.listid = @id ORDER BY name ASC', N'@id INT', @id=1234; ...and this tends to perform as badly as version A. Thanks in advance,

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  • SQL query - choosing 'last updated' record in a group, better db design?

    - by Jimmy
    Hi, Let's say I have a MySQL database with 3 tables: table 1: Persons, with 1 column ID (int) table 2: Newsletters, with 1 column ID (int) table 3: Subscriptions, with columns Person_ID (int), Newsletter_ID (int), Subscribed (bool), Updated (Datetime) Subscriptions.Person_ID points to a Person, and Subscription.Newsletter_ID points to a Newsletter. Thus, each person may have 0 or more subscriptions to 0 or more magazines at once. The table Subscriptions will also store the entire history of each person's subscriptions to each newsletter. If a particular Person_ID-Newsletter_ID pair doesn't have a row in the Subscriptions table, then it's equivalent to that pair having a subscription status of 'false'. Here is a sample dataset Persons ID 1 2 3 Newsletters ID 4 5 6 Subscriptions Person_ID Newsletter_ID Subscribed Updated 2 4 true 2010-05-01 3 4 true 2010-05-01 3 5 true 2010-05-10 3 4 false 2010-05-15 Thus, as of 2010-05-16, Person 1 has no subscription, Person 2 has a subscription to Newsletter 4, and Person 3 has a subscription to Newsletter 5. Person 3 had a subscription to Newsletter 4 for a while, but not anymore. I'm trying to do 2 kinds of query. A query that shows everyone's active subscriptions as of query time (we can assume that updated will never be in the future -- thus, this means returning the record with the latest 'updated' value for each Person_ID-Newsletter_ID pair, as long as Subscribed is true (if the latest record for a Person_ID-Newsletter_ID pair has a Subscribed status of false, then I don't want that record returned)). A query that returns all active subscriptions for a specific newsletter - same qualification as in 1. regarding records with 'false' in the Subscribed column. I don't use SQL/databases often enough to tell if this design is good, or if the SQL queries needed would be slow on a database with, say, 1M records in the Subscriptions table. I was using the Visual query builder tool in Visual Studio 2010 but I can't even get the query to return the latest updated record for each Person_ID-Newsletter_ID pair. Is it possible to come up with SQL queries that don't involve using subqueries (presumably because they would become too slow with a larger data set)? If not, would it be a better design to have a separate Subscriptions_History table, and every time a subscription status for a Person_ID-Newsletter-ID pair is added to Subscriptions, any existing record for that pair is moved to Subscriptions_History (that way the Subscriptions table only ever contains the latest status update for any Person_ID-Newsletter_ID pair)? I'm using .net on Windows, so would it be easier (or the same, or harder) to do this kind of queries using Linq? Entity Framework? Thanks!

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  • SQL: How to Return One DB Row from Two That Have The Same Values In Opposite Columns Using the MAX F

    - by OneSource
    Hi, This is what I'm trying to do. I have three columns in a table - ID, Column1, Column2 - with this example data: ID Column1 Column2 1     1            2 2     2            1 3     4            3 4     3            4 Since, in the first two rows, Column1 and Column2 have the same values (but in different columns), I want my MAX query to return an ID of 2. Same thing with rows 3 and 4 .... since Columns 1 and 2 have the same values (but in different columns), I want MAX(ID) to return 4. Of course, with MAX, you use Group By, but that will not work in my case. In effect, I need a Group By to work across two columns. Is this possible? If not, what's the best way to accomplish getting the IDs of 2 and 4 given the matching values that are in different columns? Thanks!

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  • DB Interface Design Optimization: Is it better to optimise for Fewer requests of smaller data size?

    - by Overflow
    The prevailing wisdom in webservices/web requests in general is to design your api such that you use as few requests as possible, and that each request returns therefore as much data as is needed In database design, the accepted wisdom is to design your queries to minimise size over the network, as opposed to minimizing the number of queries. They are both remote calls, so what gives?

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  • How can i insert large files in mysql db using php?

    - by anjan
    Hi! I want to upload a large file of size 10M max to my mysql database. Using .htaccess i changed the PHP's own file upload limit to "10485760" = 10M, i am able to upload files upto 10M size without any problem. But i can not insert the file in database if it is more that 1M in size. i am using file_get_contents to read all file data and pass it to the insert query as a string to be inserted into a LONGBLOB field. But files with more than 1M size is not being added to database, though i can use print_r($_FILES) to examine that the file uploaded correctly. Any help will be appreciated and i will need it within next 6 hours. So, please help! best regards, Anjan

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  • Threaded Django task doesn't automatically handle transactions or db connections?

    - by Gabriel Hurley
    I've got Django set up to run some recurring tasks in their own threads, and I noticed that they were always leaving behind unfinished database connection processes (pgsql "Idle In Transaction"). I looked through the Postgres logs and found that the transactions weren't being completed (no ROLLBACK). I tried using the various transaction decorators on my functions, no luck. I switched to manual transaction management and did the rollback manually, that worked, but still left the processes as "Idle". So then I called connection.close(), and all is well. But I'm left wondering, why doesn't Django's typical transaction and connection management work for these threaded tasks that are being spawned from the main Django thread?

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  • Zend Framework multiple databases

    - by Uffo
    I'm currently using only one database with Zend Framework, but now I have to add ONE MORE. I'm using this code right now: public static function setupDatabase() { $config = self::$registry->configuration; $db = Zend_Db::factory($config->db->adapter, $config->db->toArray()); $db->query("SET NAMES 'utf8'"); self::$registry->database = $db; Zend_Db_Table::setDefaultAdapter($db); } What code do I need to write in order to use ONE MORE database; and how I will reference it, when I need to make some queries or so.. Best Regards!

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  • What's the proper way to use sqlite at xCode?

    - by Elliot Chen
    Hi, Experts: Can you please give some suggestions on sqlite using at xcode? Within my application, I use a sqlite DB to store all local data. Two methods can be used to retrieve those data during running time. 1, Load all the data into memory at initialization stage. (More memory used, less DB open/close operation needed) 2, Read corresponding records when necessary, free the occupied memory after using. (Good habit for memory using, but much DB open/close operations needs). I prefer to use method 2, but not sure whether too many DB opening/closing operations could affect app's efficiency. Or do you think I can 'upgrade' method 2 by opening DB when app launches and closing DB when app quits? Thanks for your suggestions very much!

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  • How do I Order on common attribute of two models in the DB?

    - by Will
    If i have two tables Books, CDs with corresponding models. I want to display to the user a list of books and CDs. I also want to be able to sort this list on common attributes (release date, genre, price, etc.). I also have basic filtering on the common attributes. The list will be large so I will be using pagination in manage the load. items = [] items << CD.all(:limit => 20, :page => params[:page], :order => "genre ASC") items << Book.all(:limit => 20, :page => params[:page], :order => "genre ASC") re_sort(items,"genre ASC") Right now I am doing two queries concatenating them and then sorting them. This is very inefficient. Also this breaks down when I use paging and filtering. If I am on page 2 of how do I know what page of each table individual table I am really on? There is no way to determine this information without getting all items from each table. I have though that if I create a new Class called items that has a one to one relationship with either a Book or CD and do something like Item.all(:limit => 20, :page => params[:page], :include => [:books, :cds], :order => "genre ASC") However this gives back an ambiguous error. So can only be refined as Item.all(:limit => 20, :page => params[:page], :include => [:books, :cds], :order => "books.genre ASC") And does not interleave the books and CDs in a way that I want. Any suggestions.

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  • DB Architecture : Linking to intersection or to main tables?

    - by Jean-Nicolas
    Hi, I'm creating fantasy football system on my website but i'm very confuse about how I should link some of my table. Tables The main table is Pool which have all the info about the ruling of the fantasy draft. A standard table User, which contains the usual stuff. Intersection table called pools_users which contains id,pool_id,user_id because a user could be in more than one pool, and a pool contains more than 1 user. The problem Table Selections = that's the table that is causing problem. That's the selection that the user choose for his pool. This is related to the Player table but thats not relevant for this problem. Should I link this table to the table Pools_users or should I link it with both main table Pool and User. This table contains id,pool_id,user_id,player_id,... What is the best way link my tables? When I want to retrieve my data, I normally want the information to be divided BY users. "This user have those selections, this one those selections, etc).

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  • Need a cleaner way, which avoids too many 'if statements', to write this method for inputing data in

    - by indiehacker
    What is the best way to reference datastore model attributes without using the four 'if statements' I have in the below sample code, which seem messy and inefficient. For real-world code I may have a situation of 100 attributes such as self.var1, self.var2, ... self.varN that I want to some how reference with just an integer (or strings) as an argument to some method. class PixelObject(db.Model): zoom0 = db.ListProperty(int) zoom1 = db.ListProperty(int) zoom2 = db.ListProperty(int) zoom3 = db.ListProperty(int) zoom4 = db.ListProperty(int) def inputZoomData(self, zoomInteger, input_data): """input_data goes to specified attribute based on if 0,1,2,3,or 4 is argument""" if zoomInteger == 0: self.zoom0 = input_data if zoomInteger == 1: self.zoom1 = input_data if zoomInteger == 2: self.zoom2 = input_data if zoomInteger == 3: self.zoom3 = input_data if zoomInteger == 4: self.zoom4 = input_data

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  • In Entity framework, we can use Model first, DB first, Code first but how can we create table programmatically

    - by AukI
    In entity framework we can use 3 approaches model first , code first , database first but each one of them needs manual hand touch(means creating database or create model or write the POCO class codes or entity class codes) before proceeding to the next step ( using EF in context ). What if I want to create database and tables and table relationships programatically and still want to have to features of EntityFramework 4.3. To be more specific , from this example http://support.microsoft.com/kb/307283 we can create database , tables and everything using SQL command but we can't have the advantages of entity framework. So if we want to have that what should we do?

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  • Can you modify SQL DB schema in a transaction to know if all changes were applied?

    - by Chris F
    As part of my (new) database version control methodology, I'm writing a "change script" and want the change script to insert a new row into the SchemaChangeLog table if the script is executed successfully, or to reverse changes if any single change in the script fails. Is it possible to do schema changes in a transaction and only if it gets committed to then do the INSERT? For example (psuedo-code, I'm not too good with SQL): SET XACT_ABORT ON BEGIN TRANSACTION PRINT 'Add Col2 to Table1' IF NOT EXIST (SELECT * FROM sys.columns WHERE NAME='Col2' AND object_id=OBJECT_ID('Table1')) BEGIN ALTER TABLE [dbo].[Table1] ADD Col2 int NULL END -- maybe COMMIT here? INSERT INTO SchemaChangeLog VALUES(...) COMMIT TRANSACTION

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  • Displaying Longitude and Latitude values stored in a SQLite db as a Route on a MapView in Android (N

    - by LordSnoutimus
    I am currently in the process of creating an application that records current location of a mobile device in intervals, displaying the route as a coloured line on the device in real-time. At the same time the application is storing the longitude and latitude in a SQLite database as I want the user to be able to bring up that specific route again. The route has a primary key and each waypoint is linked to that route by a foreign key. What would be the easiest way to display the saved route on the map?.

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