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• How often to run getWritableDatabase() and getReadableDatabase()?

  - by jawonlee

  I'm writing a Service, a Content Provider, and one or more apps. The Service writes new data to the Content Provider's SQLite database every 5 minutes or so plus at user input, and is intended to run pretty much forever in the background. The app, when running, will display data pulled from the Content Provider, and will be refreshed whenever the Service puts more data into the Content Provider's database. Given that the Service only inserts into the database once every five minutes, when is the right time to call SQLiteOpenHelper's getWritableDatabase() / getReadableDatabase()? Is it on the onCreate() of the Content Provider, or should I run it every time there is an insert() and close it at the end of insert()? The data being inserted every 5 minutes will contain multiple inserts.

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• How to programmatically fill a database

  - by Dwaine Bailey

  Hi There, I currently have an iPhone app that reads data from an external XML file at start-up, and then writes this data to the database (it only reads/writes data that the user's app has not seen before, though) My concern is that there is going to be a back catalogue of data of several years, and that the first time the user runs the app it will have to read this in and be atrociously slow. Our proposed solution is to include this data "pre-built" into the applications database, so that it doesn't have to load in the archival data on first-load - that is already in the app when they purchase it. My question is whether there is a way to automatically populate this data with data from, say, an XML file or something. The database is in SQLite. I would populate it by hand, but obviously this will take a very long time, so I was just wondering if anybody had a more...programmatic solution...

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• Import data from .xls File

  - by tek3

  HI, I am developing an application in which i have to get data from .xls file. I am fairly new to iPhone development so any pointers in direction to getting started will be very much helpful. The steps that i am thinking are : 1) First i need to convert .xls to .csv Format. 2)Import the data from .csv file to SQlite Databse or Core Data.(I am not familier with any one of them, so kindly suggest which one to choose. I am looking forward to use Core Data) Am I thinking in the right direction. Will be greatful for any kind of assistance.. Thanx in advance..

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• proper Django ORM syntax to make this code work in MySQL

  - by gtujan

  I have the following django code working on an sqlite database but for some unknown reason I get a syntax error if I change the backend to MySQL...does django's ORM treat filtering differently in MySQL? def wsjson(request,imei): wstations = WS.objects.annotate(latest_wslog_date=Max('wslog__date'),latest_wslog_time=Max('wslog__time')) logs = WSLog.objects.filter(date__in=[b.latest_wslog_date for b in wstations],time__in=[b.latest_wslog_time for b in wstations],imei__exact=imei) data = serializers.serialize('json',logs) return HttpResponse(data,'application/javascript') The code basically gets the latest logs from WSlog corresponding to each record in WS and serializes it to json. Models are defined as: class WS(models.Model): name = models.CharField(max_length=20) imei = models.CharField(max_length=15) description = models.TextField() def __unicode__(self): return self.name class WSLog(models.Model): imei = models.CharField(max_length=15) date = models.DateField() time = models.TimeField() data1 = models.DecimalField(max_digits=8,decimal_places=3) data2 = models.DecimalField(max_digits=8,decimal_places=3) WS = models.ForeignKey(WS) def __unicode__(self): return self.imei

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• SELECT subset from two tables and LEFT JOIN results

  - by Doctor Trout

  Hi all, I'm trying to write a bit of SQL for SQLITE that will take a subset from two tables (TableA and TableB) and then perform a LEFT JOIN. This is what I've tried, but this produces the wrong result: Select * from TableA Left Join TableB using(key) where TableA.key2 = "xxxx" AND TableB.key3 = "yyyy" This ignore cases where key2="xxxx" but key3 != "yyyy". I want all the rows from TableA that match my criteria whether or not their corresponding value in TableB matches, but only those rows from TableB that match both conditions. I did manage to solve this by using a VIEW, but I'm sure there must be a better way of doing this. It's just beginning to drive me insane tryng to solve it now. (Thanks for any help, hope I've explained this well enough).

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• Sqlite iPhone data insertion problem

  - by Asad Khan

  Hi I have a function which basically tries to insert some data returned from a REST call. - (void)syncLocalDatabase{ NSString *file = [[NSBundle mainBundle] pathForResource:@"pickuplines" ofType:@"db"]; NSMutableString *query = [[NSMutableString alloc] initWithFormat:@""]; sqlite3 *database = NULL; char *errorMsg = NULL; if (sqlite3_open([file UTF8String], &database) == SQLITE_OK) { for(PickUpLine *pickupline in pickUpLines){ [query appendFormat:@"INSERT INTO pickuplines VALUES(%d,%d,%d,'%@','YES')", pickupline.line_id, pickupline.thumbsUps, pickupline.thumbsDowns, [pickupline.line stringByReplacingOccurrencesOfString:@"'" withString:@"`"]]; NSLog(query); int result = sqlite3_exec(database, [query UTF8String], NULL, NULL, &errorMsg); if (result!=SQLITE_OK) { printf("\n%s",errorMsg); sqlite3_free(errorMsg); } //sqlite3_step([query UTF8String]); [query setString:@""]; }//end for }//end if [query release]; sqlite3_close(database); } everything seems fine query string in log statement is also fine but the data does not gets inserted. Where as a counterpart of this function for select statement works well. Here is the counter part - (void)loadLinesFromDatabase{ NSString *file = [[NSBundle mainBundle] pathForResource:@"pickuplines" ofType:@"db"]; sqlite3 *database = NULL; if (sqlite3_open([file UTF8String], &database) == SQLITE_OK) { sqlite3_exec(database, "SELECT * FROM pickuplines", MyCallback, linesFromDatabase, NULL); } sqlite3_close(database); } I have implemented callback & it works fine. I am a little new to Sqlite can someone please point out what am I doing wrong. Thanx

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• Is re-using a Command and Connection object in ado.net a legitimate way of reducing new object creat

  - by Neil Trodden

  The current way our application is written, involves creating a new connection and command object in every method that access our sqlite db. Considering we need it to run on a WM5 device, that is leading to hideous performance. Our plan is to use just one connection object per-thread but it's also occurred to us to use one global command object per-thread too. The benefit of this is it reduces the overhead on the garbage collector created by instantiating objects all over the place. I can't find any advice against doing this but wondered if anyone can answer definitively if this is a good or bad thing to do, and why?

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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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• retrieve columns from sqlite3

  - by John Smith

  I have two tables in sqlite: CREATE TABLE fruit ('fid' integer, 'name' text); CREATE TABLE basket ('fid1' integer, 'fid2' integer, 'c1' integer, 'c2' integer); basket is supposed to have count c1 of fruit fid1 and c2 of fruit fid2 I created a view fruitbasket; create view fruitbasket as select * from basket inner join fruit a on a.fid=basket.fid1 inner join fruit b on b.fid=basket.fid2; it works (almost) as expected. When I type pragma table_info(fruitbasket); I get the following output 0|fid1|integer|0||0 1|fid2|integer|0||0 2|c1|integer|0||0 3|c2|integer|0||0 4|fid|integer|0||0 5|name|text|0||0 6|fid:1|integer|0||0 7|name:1|text|0||0 The problem is that I cannot seem to SELECT name:1. How can I do it other than going back and re-aliasing the columns?

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• How to discover table properties from SQLAlchemy mapped object

  - by ssaboum

  Hi, My point is i have a class mapped with a table, in my case in a declarative way, and i want to "discover" table properties, columns, names, relations, from this class : engine = create_engine('sqlite:///' + databasePath, echo=True) # setting up root class for declarative declaration Base = declarative_base(bind=engine) class Ship(Base): __tablename__ = 'ships' id = Column(Integer, primary_key=True) name = Column(String(255)) def __init__(self, name): self.name = name def __repr__(self): return "<Ship('%s')>" % (self.name) So now my goal is from the "Ship" class to get the table columns and their properties from another piece of code. I guess i can deal with it using instrumentation but is there any way provided by the SQLAlchemy API ? Thank you.

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• Is there a library / tool to query MySQL data files (MyISAM / InnoDB) without the server? (the SQLit

  - by MGW

  Oftentimes I want to query my MySQL data directly without a server running or without having access to the server (but having read / write rights to the files). Is there a tool or maybe even a library around to query MySQL data files like it is possible with SQLite? I'm specifically looking for InnoDB and MyISAM support. Performance is not a factor. I don't have any knowledge about MySQL internals, but I presume it should be possible to do and not too hard to get the specific code out? Thank you for any suggestions!

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• How to correctly do SQL UPDATE with weighted subselect?

  - by luminarious

  I am probably trying to accomplish too much in a single query, but have I an sqlite database with badly formatted recipes. This returns a sorted list of recipes with relevance added: SELECT *, sum(relevance) FROM ( SELECT *,1 AS relevance FROM recipes WHERE ingredients LIKE '%milk%' UNION ALL SELECT *,1 AS relevance FROM recipes WHERE ingredients LIKE '%flour%' UNION ALL SELECT *,1 AS relevance FROM recipes WHERE ingredients LIKE '%sugar%' ) results GROUP BY recipeID ORDER BY sum(relevance) DESC; But I'm now stuck with a special case where I need to write the relevance value to a field on the same row as the recipe. I figured something along these lines: UPDATE recipes SET relevance=(SELECT sum(relevance) ...) But I have not been able to get this working yet. I will keep trying, but meanwhile please let me know how you would approach this?

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• How do I get the CoreData Debug argument to output to the console?

  - by radesix

  According to Apple documentation on debugging Core Data it says we should be able to pass an argument to the application which will output the SQL core data sends to SQLite. I have gone into the arguments tab of my executable in XCode and specified the argument: -com.apple.CoreData.SQLDebug 1 However, I see no SQL in the console. I then tried to use this parameter in the CoreDataBooks application provided by Apple just in case there was some other issue in MY program. Even in Apple's example I get no SQL output in the console. Am I doing something wrong? Is Apple's documentation wrong? Should I be looking someplace other than the console? Has anyone else had success with this argument?

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• How to add user customized data to database?

  - by CSharperWithJava

  I am trying to design a sqlite database that will store notes. Each of these notes will have common fields like title, due date, details, priority, and completed. In addition though, I would like to add data for more specialized notes like price for shopping list items and author/publisher data for books. I also want to have a few general purpose fields that users can fill with whatever text data they want. How can I design my database table in this case? I could just have a field for each piece of data for every note, but that would waste a lot of fields and I'd like to have other options and suggestions.

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• Notepad Tutorial: deleteDatabase() function

  - by FelixA

  Hello I have a short question to the notepad tutorial on the android website. I wrote a simple function in the tutorial code to delete the whole database. It looks like this: DataHelper.java public void deleteDatabase() { this.mDb.delete(DATABASE_NAME, null, null); } Notepadv1.java @Override public boolean onCreateOptionsMenu(Menu menu) { boolean result = super.onCreateOptionsMenu(menu); menu.add(0, DELETE_ID, 0, "Delete whole Database"); return result; } @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case DELETE_ID: mDbHelper.deleteDatabase(); return true; } return super.onOptionsItemSelected(item); } But when I run the app and try to delete the database I will get this error in LogCat: sqlite returned: error code = 1, msg= no such table: data Can you help how to fix this problem. It seems that the function deleteDatabase can not reach the database. Thank you very much. Felix

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• Is this SQL select code following good practice?

  - by acidzombie24

  I am using sqlite and will port to mysql (5) later. I wanted to know if I am doing something I shouldnt be doing. I tried purposely to design so I'll compare to 0 instead of 1 (I changed hasApproved to NotApproved to do this, not a big deal and I haven't written any code). I was told I never need to write a subquery but I do here. My Votes table is just id, ip, postid (I don't think I can write that subquery as a join instead?) and that's pretty much all that is on my mind. Naming conventions I don't really care about since the tables are created via reflection and is all over the place. select id, name, body, upvotes, downvotes, (select 1 from UpVotes where IPAddr=? AND post=Post.id) as myup, (select 1 from DownVotes where IPAddr=@0 AND post=Post.id) as mydown from Post where flag = '0' limit ?, ?"

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• Help with optimising SQL query

  - by user566013

  Hi i need some help with this problem. I am working web application and for database i am using sqlite. Can someone help me with one query from databse which must be optimized == fast =) I have table x: ID | ID_DISH | ID_INGREDIENT 1 | 1 | 2 2 | 1 | 3 3 | 1 | 8 4 | 1 | 12 5 | 2 | 13 6 | 2 | 5 7 | 2 | 3 8 | 3 | 5 9 | 3 | 8 10| 3 | 2 .... ID_DISH is id of different dishes, ID_INGREDIENT is ingredient which dish is made of: so in my case dish with id 1 is made with ingredients with ids 2,3 In this table a have more then 15000 rows and my question is: i need query which will fetch rows where i can find ids of dishes ordered by count of ingreedients ASC which i haven added to my algoritem. examle: foo(2,4) will rows in this order: ID_DISH | count(stillMissing) 10 | 2 1 | 3 Dish with id 10 has ingredients with id 2 and 4 and hasn't got 2 more, then is

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• Behaviour to simulate an enum implementing an interface

  - by fearofawhackplanet

  Say I have an enum something like: enum OrderStatus { AwaitingAuthorization, InProduction, AwaitingDespatch } I've also created an extension method on my enum to tidy up the displayed values in the UI, so I have something like: public static string ToDisplayString(this OrderStatus status) { switch (status) { case Status.AwaitingAuthorization: return "Awaiting Authorization"; case Status.InProduction: return "Item in Production"; ... etc } } Inspired by the excellent post here, I want to bind my enums to a SelectList with an extension method: public static SelectList ToSelectList<TEnum>(this TEnum enumObj) however, to use the DisplayString values in the UI drop down I'd need to add a constraint along the lines of : where TEnum has extension ToDisplayString Obviously none of this is going to work at all with the current approach, unless there's some clever trick I don't know about. Does anyone have any ideas about how I might be able to implement something like this?

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• Python/Sqlite app for web or desktop?

  - by ChrisC

  I am in the planning stages of rewriting an Access db I wrote several years ago in a full fledged program. I have very slight experience coding, but not enough to call myself a programmer by far. I'll definitely be learning as I go, so I'd like to keep everything as simple as possible. I've decided on Python and SQLite for my program, but I need help on my next decision. Here is my situation 1) It'll be a desktop program, run locally on each machine, all Windows 2) I want a nice looking GUI with colors, different shaped buttons, nice menus, lists, etc, etc 3) I'm thinking about using a browser interface because (a) from what I've read, browser apps can look really great, and (b) I understand there are lots of free tools to assist in setting up the GUI/GUI code with drag and drop tools, so that helps my "keep it simple" goal. 4) I want the program to be totally portable so it runs completely from one single folder on a user's PC. If I do go the browser app router, a major concern I have is the possibility that a user's browser settings could affect or break the app. How likely is this? What other pros and cons are there for my situation?

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• Getting records from a table based on a filter field and Between but also having the OR login for mu

  - by Pentium10

  I have a this table, where I store multiple ids and an age range (def1,def2) CREATE TABLE "template_requirements" ("_id" INTEGER NOT NULL, "templateid" INTEGER, "def1" VARCHAR(255), "def2" VARCHAR(255), PRIMARY KEY("_id")) Having values such as: templateid | def1 | def2 100 | 7 | 25 200 | 40 | 90 300 | 7 | 25 300 | 40 | 60 as you see for templateid 300 we have an or logic: age between 7 and 25 or age between 40 and 60. I want to get all the template ids that are not for a certain age like 25... What's the problem? If I run a query like this one: SELECT group_concat(templateid) FROM template_requirements where and '25' not between cast(def1 as integer) and cast(def2 as integer) it returns 200, 300, which is wrong, as the 300 matched on row 40 to 60, but shouldn't be included in the result as we have a condition with same templateid 7 to 25 that fails the not beetween stuff. How would be the correct query in SQLite, I would like to keep the group_concat stuff.

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• Efficient way to access a mapping of identifiers in Python

  - by sixbelo

  I am writing an app to do a file conversion and part of that is replacing old account numbers with a new account numbers. Right now I have a CSV file mapping the old and new account numbers with around 30K records. I read this in and store it as dict and when writing the new file grab the new account from the dict by key. My question is what is the best way to do this if the CSV file increases to 100K+ records? Would it be more efficient to convert the account mappings from a CSV to a sqlite database rather than storing them as a dict in memory?

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• iPhone SDK: Data Synchronization

  - by buzzappsoftware

  I am looking for an overview of data synchronization techniques available on the iPhone platform. We need the ability to be able to sync a subset of content from a server to a local database residing on the iPhone. On other projects I have worked on, the data synchronization was handled by the database. Is that available in SQLite? If not, any suggestions on techniques? Rolling our own would not be my first choice. Thanks in advance.

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• When is BIG, big enough for a database?

  - by David ???

  I'm developing a Java application that has performance at its core. I have a list of some 40,000 "final" objects, i.e., I have an initialization input data of 40,000 vectors. This data is unchanged throughout the program's run. I am always preforming lookups against a single ID property to retrieve the proper vectors. Currently I am using a HashMap over a sub-sample of a 1,000 vectors, but I'm not sure it will scale to production. When is BIG, actually big enough for a use of DB? One more thing, an SQLite DB is a viable option as no concurrency is involved, so I guess the "threshold" for db use, is perhaps lower.

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• DLL Load Failed: %1 is not a valid win32 application

  - by glittershark

  So I have a situation where I need to make binary patches and then be able to apply them from within python. I found bsdiff which looks like a great algorithm and has a python extension module, but that extension module doesn't have a windows installer past Python 2.5 Alright, so having never even written C seriously, let alone attempted a python extension module, I set out to compile it myself. After a few hours of bashing my head against a DLL load error with MinGW32, I managed to get it compiled and built using the setup.py provided in the source of the project. However, upon importing the resulting bsdiff module, I get: ImportError: DLL load failed: %1 is not a valid Win32 application. Any advice?

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• Programmatically set browser cookie (Firefox)

  - by Andrew

  I know from this question that Firefox 3.0 and up stores its cookies in an SQLite database. My question is: can you access this database from other desktop programs in such a way that you could add a cookie? I realize this has security implications. However, I do not want to read them at all. I want to be able to set one cookie if possible. I don't even want to overwrite a cookie. I just want to add it if it isn't there already. This is sort of a personal project I'm working on for fun. This question is mostly language agnostic. I would prefer a solution in C#, but proof of concept in any language will suffice. Extra credit: It would be cool to set the same cookie in Internet Explorer, too

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