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• Pervasive database backup

  - by Steven

  I'm looking for the best way to backup my pervasive database. I've read the documentation but still have a few questions. It appears that Continuous Operations method only allows me to backup the entire database? So I'd do butil -startbu @filelist, then backup the entire database (copy, rsync, etc), then run butil -endbu @filelist. Looking through the documentation I don't see a way to get transaction logs out of this method; like I would do for MSSQL (BACKUP LOG ACCT TO DISK) or Postgres (archive_command). With rsync, it might be feasible to still do this every 15 minutes. The Archival Logging method means I would have to occasionally stop the database to get a full backup, which is acceptable for me. But can I copy the log files off of the server every 15 minutes, ie log shipping? Thank you.

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• Specifying Multiplicity in a Visio Database (ERD) Diagram

  - by Nitrodist

  Is there a way to manually edit the cardinality/multiplicity symbols on the end of a database ERD made in Visio? The category I'm using is in Visio 2003 under Database -> Database Model Diagram I want to be able to go from something like this: To this: The second graphic was done by manually adding the numbers, but I would prefer to just do it in Visio. Is there any way of accomplishing this?

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• SQL Server 2008 login problem with ASP.NET application: Failed to open the explicitly specified database

  - by eulerfx

  I am running SQL Server 2008 Express Edition on Windows Server 2008 with an ASP.NET application which must access the server. The ASP.NET application is associated with an application pool that runs on the NetworkService account. This account in turn has a Login and User record on SQL Server in the required database. When I attempt to run the ASP.NET website I get a blank page and when viewed in the error log, I seem to be getting this information event record: Login failed for user 'NT AUTHORITY\NETWORK SERVICE'. Reason: Failed to open the explicitly specified database. [CLIENT: myLocalMachine] The connection string has Trusted_Connection=True; and the required database specified. When I explicitly specify the user name and password I get another login error stating the password is incorrect, even though the same un/pw combination works through SQL Server Management studio. The NETWORK SERVICE account seems to have all the required privileges for the database. Also, I made a test ASP.NET website project which does a simple select from a table in that database, and using the same config file I am not getting the error and it seems to work. Is it something to do with trust levels then, because the original ASP.NET web app references various DLLs including open source libraries. Also, the application does not seem to be able to write to the event log itself, throwing a security exception, even though everything in the config files, including machine.config states the app is in full trust.

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• Django - Moving database from development to production servers

  - by Garfonzo

  I am working on a Django project with a MySQL backend. I'm curious about the best way to update a production server's database to reflect the changes made on the development server's database? When I develop now, I make some changes to a models.py file, then to a schemamigration using South. Sometimes I do several migrations across several apps within the main project folder before it's ready for the production database. This means that there are several migration files in the app/migrations/ folder created by South. So on the production server, how does one update the database to reflect all the changes made in development, without having any data loss?

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• Index fragmentation and reorganizing database pages

  - by TiQ

  Say you have a database with heavy index fragmentation. Say this database also has a lot of free space due to frequent deletes in its data file. This free space is not contiguous. If I rebuild all indexes to remove fragmentation and then reorganize the database pages so allocated pages and free pages are contiguous, would this cause further fragmentation in my indexes? I guess the question can be posed as: if it matters, which should I do first, reorganize or rebuild?

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• Granting rights on postgresql database to another user

  - by Austin

  I'm trying to set up a system with a PostgreSQL database per user, with a PHP-FPM resource pool for an associated account. I need to grant all privileges on the database to the other user, but it seems that it's only possible to do this for tables. I've tried grant all privileges on database username to username_shadow but this gives only limited privileges. I've upgraded to PGSQL 9.2, which has the ability to grant privileges on schema, but I can't get a useful result. How do I simply make another user have all the privileges of the first on the same database?

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• mySQL Optimization Suggestions

  - by Brian Schroeter

  I'm trying to optimize our mySQL configuration for our large Magento website. The reason I believe that mySQL needs to be configured further is because New Relic has shown that our SELECT queries are taking a long time (20,000+ ms) in some categories. I ran MySQLTuner 1.3.0 and got the following results... (Disclaimer: I restarted mySQL earlier after tweaking some settings, and so the results here may not be 100% accurate): >> MySQLTuner 1.3.0 - Major Hayden <[email protected]> >> Bug reports, feature requests, and downloads at http://mysqltuner.com/ >> Run with '--help' for additional options and output filtering [OK] Currently running supported MySQL version 5.5.37-35.0 [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MRG_MYISAM [--] Data in MyISAM tables: 7G (Tables: 332) [--] Data in InnoDB tables: 213G (Tables: 8714) [--] Data in PERFORMANCE_SCHEMA tables: 0B (Tables: 17) [--] Data in MEMORY tables: 0B (Tables: 353) [!!] Total fragmented tables: 5492 -------- Security Recommendations ------------------------------------------- [!!] User '@host5.server1.autopartsnetwork.com' has no password set. [!!] User '@localhost' has no password set. [!!] User 'root@%' has no password set. -------- Performance Metrics ------------------------------------------------- [--] Up for: 5h 3m 4s (5M q [317.443 qps], 42K conn, TX: 18B, RX: 2B) [--] Reads / Writes: 95% / 5% [--] Total buffers: 35.5G global + 184.5M per thread (1024 max threads) [!!] Maximum possible memory usage: 220.0G (174% of installed RAM) [OK] Slow queries: 0% (6K/5M) [OK] Highest usage of available connections: 5% (61/1024) [OK] Key buffer size / total MyISAM indexes: 512.0M/3.1G [OK] Key buffer hit rate: 100.0% (102M cached / 45K reads) [OK] Query cache efficiency: 66.9% (3M cached / 5M selects) [!!] Query cache prunes per day: 3486361 [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 812K sorts) [!!] Joins performed without indexes: 1328 [OK] Temporary tables created on disk: 11% (126K on disk / 1M total) [OK] Thread cache hit rate: 99% (61 created / 42K connections) [!!] Table cache hit rate: 19% (9K open / 49K opened) [OK] Open file limit used: 2% (712/25K) [OK] Table locks acquired immediately: 100% (5M immediate / 5M locks) [!!] InnoDB buffer pool / data size: 32.0G/213.4G [OK] InnoDB log waits: 0 -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance MySQL started within last 24 hours - recommendations may be inaccurate Reduce your overall MySQL memory footprint for system stability Enable the slow query log to troubleshoot bad queries Increasing the query_cache size over 128M may reduce performance Adjust your join queries to always utilize indexes Increase table_cache gradually to avoid file descriptor limits Read this before increasing table_cache over 64: http://bit.ly/1mi7c4C Variables to adjust: *** MySQL's maximum memory usage is dangerously high *** *** Add RAM before increasing MySQL buffer variables *** query_cache_size (> 512M) [see warning above] join_buffer_size (> 128.0M, or always use indexes with joins) table_cache (> 12288) innodb_buffer_pool_size (>= 213G) My my.cnf configuration is as follows... [client] port = 3306 [mysqld_safe] nice = 0 [mysqld] tmpdir = /var/lib/mysql/tmp user = mysql port = 3306 skip-external-locking character-set-server = utf8 collation-server = utf8_general_ci event_scheduler = 0 key_buffer = 512M max_allowed_packet = 64M thread_stack = 512K thread_cache_size = 512 sort_buffer_size = 24M read_buffer_size = 8M read_rnd_buffer_size = 24M join_buffer_size = 128M # for some nightly processes client sessions set the join buffer to 8 GB auto-increment-increment = 1 auto-increment-offset = 1 myisam-recover = BACKUP max_connections = 1024 # max connect errors artificially high to support behaviors of NetScaler monitors max_connect_errors = 999999 concurrent_insert = 2 connect_timeout = 5 wait_timeout = 180 net_read_timeout = 120 net_write_timeout = 120 back_log = 128 # this table_open_cache might be too low because of MySQL bugs #16244691 and #65384) table_open_cache = 12288 tmp_table_size = 512M max_heap_table_size = 512M bulk_insert_buffer_size = 512M open-files-limit = 8192 open-files = 1024 query_cache_type = 1 # large query limit supports SOAP and REST API integrations query_cache_limit = 4M # larger than 512 MB query cache size is problematic; this is typically ~60% full query_cache_size = 512M # set to true on read slaves read_only = false slow_query_log_file = /var/log/mysql/slow.log slow_query_log = 0 long_query_time = 0.2 expire_logs_days = 10 max_binlog_size = 1024M binlog_cache_size = 32K sync_binlog = 0 # SSD RAID10 technically has a write capacity of 10000 IOPS innodb_io_capacity = 400 innodb_file_per_table innodb_table_locks = true innodb_lock_wait_timeout = 30 # These servers have 80 CPU threads; match 1:1 innodb_thread_concurrency = 48 innodb_commit_concurrency = 2 innodb_support_xa = true innodb_buffer_pool_size = 32G innodb_file_per_table innodb_flush_log_at_trx_commit = 1 innodb_log_buffer_size = 2G skip-federated [mysqldump] quick quote-names single-transaction max_allowed_packet = 64M I have a monster of a server here to power our site because our catalog is very large (300,000 simple SKUs), and I'm just wondering if I'm missing anything that I can configure further. :-) Thanks!

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• SQL database testing: How to capture state of my database for rollback.

  - by Rising Star

  I have a SQL server (MS SQL 2005) in my development environment. I have a suite of unit tests for some .net code that will connect to the database and perform some operations. If the code under test works correctly, then the database should be in the same (or similar) state to how it was before the tests. However, I would like to be able to roll back the database to its state from before the tests run. One way of doing this would be to programmatically use transactions to roll back each test operation, but this is difficult and cumbersome to program; it could easily lead to errors in the test code. I would like to be able to run my tests confidently knowing that if they destroy my tables, I can quickly restore them? What is a good way to save a snapshot of one of my databases with its tables so that I can easily restore the database to it's state from before the test?

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• mysqldump isn't able to export a specific database, phpMyAdmin crashes

  - by Devils Child

  I'm experiencing problems with a database on my server (Note: All other databases work fine). Once I try to export it with mysqldump I get this error: # mysqldump -u root -pXXXXXXXXX databasename > /root/databasename.sql mysqldump: Couldn't execute 'show table status like 'apps'': Lost connection to MySQL server during query (2013) Also, phpMyAdmin throws an error when selecting this database and immediately logs out. However, the web site which uses this database works fine. I can also execute SELECT statements on the table named "apps" from the MySQL shell. I tried restarting the MySQL daemon as well as REPAIR DATABASE and REPAIR TABLE but the problem still persists. I had this problem before, then it disappeared somehow without me doing anything to resolve the issue. Now, the problem is back and I'm simply unable to create a backup of this database. Used software Debian 6.0.7 x64 MySQL 5.1.66-0 MySQL Version: mysql> SHOW VARIABLES LIKE "%version%"; +-------------------------+-------------------+ | Variable_name | Value | +-------------------------+-------------------+ | protocol_version | 10 | | version | 5.1.66-0+squeeze1 | | version_comment | (Debian) | | version_compile_machine | x86_64 | | version_compile_os | debian-linux-gnu | +-------------------------+-------------------+

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• Delete data from a MSSQL standby database?

  - by SQL-Newbie

  Is it possible to delete data from a read only standby database that imports shipped log files? At least in my theory this shouldn't be possible because the deletion would change the LSN and the log shipping should break. What I need is a smaller sized database than the database that ships the logs. So basically I need a way to have the (readonly) standby server storing only the most recent data. Any ideas or recommendations on this?

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• Identifying Exchange 2010 regular process that is walking the mailbox database

  - by toongeneral

  I have an Exchange 2010 server running on a SAN-backed platform. The platform does block-level backups based on a snapshot/incremental basis, that only capture changed data. I was surprised to see a regular period of time where the data changes were happening at a high, sustained rate. Due to the way this system works, that can lead to 1.2TB of stored data per month. The regularity implied a scheduled task, but it is not a fixed interval. It is approximately every 26-32hrs. The disks were performing read operations of ~5MB/s and write operations of ~4.5MB/s, for a period of 3-4hrs. The total written data was ~55-60GB. Reading on TechNet, I am wondering if the following is causing this: http://blogs.technet.com/b/exchange/archive/2011/12/14/database-maintenance-in-exchange-2010.aspx#checksumming The somewhat restrictive thing is that the process only happens at most once every 24 hours. I was able to investigate while it was running, finding the following: the process is store.exe it is working on the mailbox database files while running, it is generating .log files (in the mailbox database folder) consistent with database changes the mailbox database is ~60GB in size, which fits with the total data changes on each iteration I have currently switched to a fixed maintenance window, as a test. It's not clear whether this is the cause, as the symptoms fit, but are not conclusive. Does anyone have any suggestions for additional troubleshooting?

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• Spoof database connection to be local instead of remote

  - by spydon

  I am trying to connect one of our clients "as is" programs to a remote database instead of a local one, they say that they have coded it to be able to do it, but for some reason the program crashes when trying to connect to a remote database. I don't have the source code so I can't really dig much deeper than that and the company does not provide any upgrades or custom modifications. I can succesfully connect to the database through SqlDbx and HeidiSQL so I know that the server is set up correctly. This is why I need to find a way to spoof a remote connection on port 1433 to appear like a local database connection to the program. I thought about editing the hosts file, but it will most likely crash other programs if I bind localhost to another IP than 127.0.0.1. Any ideas?

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• Problem creating sitecollection when database attached has been deleted

  - by pkspt

  Hi, I created one new sitecollection in new contentdatabase but later i changed my mind and decided to create it in the same database as of the webapplication. I deleted the sitecollection I created through newdatabase and bt now when I am creating that site again its getting attached to the new database which got created above not the same one? Any solution for that I tried deleting database which got created after deleting site collection. Now, when I when I am trying to create a site its looking for old database and giving me error as its not able to open it. Any suggestions on this one..?

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• Scaling web application with SQL Server 2008 database

  - by John

  I have a database which has 90% of read only tables. 10% of the tables has writable data. We need to scale the ASP.NET application.We need to add more users who will not be writing to the database. We are thinking of adding another server and routing the users who need read only access to that server. Is there a way to replicate just some tables to another database server. Since the 90% of data doesnt change, we don't want to setup any full database replication. Please advise.

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• Easy way to observe user activity - how improve my database structure.

  - by Thomas

  Welcome, I need some advise to improve perfomence my web application. In the begin I had this structure of database: USER -id (Primary Key) -name -password -email .... PROFILE -user Primary Key, Foreign Key (USER) -birthday -region -photoFile ... PAGES -id (Primary Key) -user Foreign Key(USER) -page -date COMMENTS -id (Primary Key) -user Foreign Key(USER) -page Foreign Key(PAGE) -comment -date FAVOURITES_PAGES -id (Primary Key) -user Foreign Key(USER) -favourite_page Foreign Key(PAGE) -date but now one of the most important page of website is observatory, when everyone can observe activity others users. So I need select all pages, comments and favourites pages some users and display it in one list, sorted by date. For better perfomance (I think) I changed my structure to this: table USER and PROFILE without changes ACTIVITY (additional table- have common fields: user,date) -id (Primary Key) -user Foreign Key(USER) -date -page Foreign Key(PAGE) -comment Foreign Key(COMMENTS) -favourite_page Foreign Key(FAVOURITES_PAGES) PAGES -id (Primary Key) -page COMMENTS -id (Primary Key) -page Foreign Key(PAGE) -comment FAVOURITES_PAGES -id (Primary Key) -favourite_page Foreign Key(PAGE) So now it is very easy get sorted records from all tables. But I have no only foreign key to PAGES, COMMENTS and FAVOURITES_PAGES in ACTIVITY table - there is about ten Foreign Key fields and in one record only one have value, others have None: ACTIVITY id user date page comment ... 1 2 2010-02-23 None 1 2 1 2010-02-21 1 None .... It is corect solution. When I display about 40 records in one page (pagination) I must wait about one secound, but database is almost emty (a few users and about 100 records in others tables). It is depends on amount records per page - I have checked it, but why it takes too long time, becouse of relationships? The website is built in Python/Django. Any advices/opinion?

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• Storing class constants (for use as bitmask) in a database?

  - by fireeyedboy

  Let's say I have a class called Medium which can represent different types of media. For instance: uploaded video embedded video uploaded image embedded image I represent these types with contants, like this: class MediumAbstract { const UPLOAD = 0x0001; const EMBED = 0x0010; const VIDEO = 0x0100; const IMAGE = 0x1000; const VIDEO_UPLOAD = 0x0101; // for convenience const VIDEO_EMBED = 0x0110; // for convenience const IMAGE_UPLOAD = 0x1001; // for convenience const IMAGE_EMBED = 0x1010; // for convenience const ALL = 0x1111; // for convenience } Thus, it is easy for me to do a combined search on them on an (abstract) repository, with something like: { public function findAllByType( $type ) { ... } } $media = $repo->findAllByType( MediumAbstract::VIDEO | MediumAbstract::IMAGE_UPLOAD ); // or $media = $repo->findAllByType( MediumAbstract::ALL ); // etc.. How do you feel about using these constant values in a concrete repository like a database? Is it ok? Or should I substitute them with meaningful data in the database. Table medium: | id | type | location | etc.. ------------------------------------------------- | 1 | use constants here? | /some/path | etc.. (Of course I'll only be using the meaningful constants: VIDEO_UPLOAD, VIDEO_EMBED, IMAGE_UPLOAD and IMAGE_EMBED)

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• What is a good programming language/environment for Linux database applications?

  - by Dkellygb

  I could use some advice on my move from the Windows world to Linux. For my business, I have used VB6 and Microsoft Access with both Access databases and SQL server in the past. The easy to use forms, report writers and programming language were perfect for CRUD apps and analysis for our small hotel/restaurant business. After using Linux at home for some time I would like to convert our small business. Our server is already a Linux box using Samba. I am happy with the OpenOffice.org applications instead of Microsoft Office. The only thing which is holding me back is a desktop database application where I can develop the forms and reports we require. Base does not seem to be up to the job yet from my experience. I would like something like VB.Net with visual studio (express) but I would like to avoid Mono – I just don’t see the point of it. (You can correct me if I’m wrong.) But a good collection of forms, controls and a good report writer would be ideal. I have looked at web based stuff like Ruby on Rails, but I think a webserver for our 5 pc network is overkill. I don’t mind running a proper database on our Ubuntu 9.10 server. I may have exposed a few prejudices above but my mind is open. Any thoughts?

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• How to inject php code from database into php script ?

  - by luxquarta

  I want to store php code inside my database and then use it into my script. class A { public function getName() { return "lux"; } } // instantiates a new A $a = new A(); Inside my database there is data like "hello {$a->getName()}, how are you ?" In my php code I load the data into a variable $string $string = load_data_from_db(); echo $string; // echoes hello {$a->getName()}, how are you ? So now $string contains "hello {$a-getName()}, how are you ?" {$a-getName()} still being un-interpretated Question: I can't find how to write the rest of the code so that {$a-getName()} gets interpretated "into hello lux, how are you". Can someone help ? $new_string = ?????? echo $new_string; //echoes hello lux, how are you ? Is there a solution with eval() ? (please no debate about evil eval ;)) Or any other solution ?

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• How can I get a iterable resultset from the database using pdo, instead of a large array?

  - by Tchalvak

  I'm using PDO inside a database abstraction library function query. I'm using fetchAll(), which if you have a lot of results, can get memory intensive, so I want to provide an argument to toggle between a fetchAll associative array and a pdo result set that can be iterated over with foreach and requires less memory (somehow). I remember hearing about this, and I searched the PDO docs, but I couldn't find any useful way to do that. Does anyone know how to get an iterable resultset back from PDO instead of just a flat array? And am I right that using an iterable resultset will be easier on memory? I'm using Postgresql, if it matters in this case. . . . The current query function is as follows, just for clarity. /** * Running bound queries on the database. * * Use: query('select all from players limit :count', array('count'=>10)); * Or: query('select all from players limit :count', array('count'=>array(10, PDO::PARAM_INT))); **/ function query($sql_query, $bindings=array()){ DatabaseConnection::getInstance(); $statement = DatabaseConnection::$pdo->prepare($sql_query); foreach($bindings as $binding => $value){ if(is_array($value)){ $statement->bindParam($binding, $value[0], $value[1]); } else { $statement->bindValue($binding, $value); } } $statement->execute(); // TODO: Return an iterable resultset here, and allow switching between array and iterable resultset. return $statement->fetchAll(PDO::FETCH_ASSOC); }

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• BackOffice Database Application FrontEnd - Program in C#/VB.Net or PHP?

  - by HK1

  I'm working on a project where there will be a MySQL database containing data that will mostly be displayed on the web using PHP. However, there is a need here for a back-office data entry application (linked to the same MySQL database) that is feature rich and easy to use. what I'm trying to understand is where we are at with web-based frontends. I find that there are still so many events and features that I can make use of in a Windows Desktop GUI written in something like C#, VB.Net or MS Access. I don't have a lot of experience programming UI for web but it's my impression that it's still more difficult and takes longer to get similar or the same functionality using non-MS web technologies (I dislike ASP.net, sorry) as compared to programming the desktop portion in a traditional desktop application language like C#, VB.Net, or MS Access. jQuery and jQuery UI are definately making things easier. Also, there's very rich online applications like Google Docs and Zoho but it's my impression that these are programmed by some of the top web UI programmers around, not to mention that it takes longer to write it and intensive testing to make it work in all of your target browsers. It also takes extra time and code to "block" browsers that don't meet the requirements. What programming language would you recommend? I know I may not have given enough information here but I'm not sure what I'm missing. If you have questions just leave a comment below so I can edit this post and answer the questions.

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• What is a mantainable way of saving "star rating" in a database?

  - by Montecristo

  I'll use the jQuery plugin for presenting the user with a nice interface The request is to display 5 stars, up to a total score of 10 (2 points per star). By now I thought about using 7/10 as a format for that value, but what if at some point in the future I'll receive a request like We would like to give users more choice, let's increase the total score to 20 (so that each star contributes with a maximum of 4 points) I'll end up with a table with mixed values for the "star rating" column: some will be like 7/10 while others will be like 14/20. Is it ok for you to have this difference in the database and deal with it in the logic layer to have it consistent? Or is preferred another way so that querying the table will not result in inconsistent results outside the application? Maybe floating point values could help me, is it better to store that value as a number less than or equal to one? So in each of the two examples the resulting value stored in the database would be 0,7, as a number, not a varchar, which can be queried also outside the application. What do you think?

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• What database options do I have for the Blackberry?

  - by peeping-jane

  I notice most of the discussions about Blackberry database options are old, and generally not too informative. As of today, March 31st, 2010, what is the best, most universally supported, free database option available for Blackberry developers? I heard SQLite is available for JDE v5, but last I checked, that was still in beta, and I didn't want to commit to developing on a system that is not supported by most of the phones in service. Thing is, I don't see any dates on these claims. For all I know, the announcements I am reading are from 2008. So, I am still on v 4.7. I need to use a relational DB for the app I am developing, but there aren't many resources for DB handling available - or at least resources that are useful to me. I find a lot of "tutorials" that assume you know everything there is to know about Blackberry development, or Java. But no complete classes or anything. Many of these examples don't even work. Eclipse gives warnings and errors from code copied and pasted from other people's examples. I can answer any questions that may assist in this case. Hopefully, this thread will help many BB developers in the future.

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• How to delete a row from a typed dataset and save it to a database?

  - by Zingam

  I am doing this as a small project to learn about disconnected and connected models in .NET 4.0 and SQL Server 2008 R2. I have three tables: Companies (PK CompanyID) Addresses (PK AddressID, FK CompanyID) ContactPersons (PK ContactPersonID, FK CompanyID) CompanyID is assigned manually by the users. The other IDs are auto-generated. Companies has a one-to-many relationship with ContactPerson. I have set any changes to cascade. I display all records in Companies in a DataGridView and when a row is clicked, the corresponding records in ContactPersons are displayed in a second DataGridView. I have successfully implemented updating and inserting new records but I completely fail in my attempts to delete rows and save the changes to the database. I us a typed dataset. If I use this: DataRow[] contactPersonRows = m_SoldaCompaniesFileDataSet.ContactPersons.Select("ContactPersonID = " + this.m_CurrentContactPerson.ContactPersonID); m_SoldaCompaniesFileDataSet.ContactPersons.Rows.Remove(contactPersonRows[0]); The records are displayed properly in the DataGridView but are not saved in the database later. If I use this: DataRow row = m_SoldaCompaniesFileDataSet.ContactPersons.Rows.Find(this.m_CurrentContactPerson.ContactPersonID); row.Delete(); The records are set but I get an exeception: DeletedRowInaccessibleException, when I try to refresh the DataGridView. The exception pop-s up in the auto-generated dataset.design file. I am pretty much stuck at this point since yesterday. I cannot find anything anywhere that remotely resembles my problem. And I cannot understand actually what is going on.

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• Designing a database for a user/points system? (in Django)

  - by AP257

  First of all, sorry if this isn't an appropriate question for StackOverflow. I've tried to make it as generalisable as possible. I want to create a database (MySQL, site running Django) that has users, who can be allocated a certain number of points for various types of action - it's a collaborative game. My requirements are to obtain: the number of points a user has the user's ranking compared to all other users and the overall leaderboard (i.e. all users ranked in order of points) This is what I have so far, in my Django models.py file: class SiteUser(models.Model): name = models.CharField(max_length=250 ) email = models.EmailField(max_length=250 ) date_added = models.DateTimeField(auto_now_add=True) def points_total(self): points_added = PointsAdded.objects.filter(user=self) points_total = 0 for point in points_added: points_total += point.points return points_total class PointsAdded(models.Model): user = models.ForeignKey('SiteUser') action = models.ForeignKey('Action') date_added = models.DateTimeField(auto_now_add=True) def points(self): points = Action.objects.filter(action=self.action) return points class Action(models.Model): points = models.IntegerField() action = models.CharField(max_length=36) However it's rapidly becoming clear to me that it's actually quite complex (in Django query terms at least) to figure out the user's ranking and return the leaderboard of users. At least, I'm finding it tough. Is there a more elegant way to do something like this? This question seems to suggest that I shouldn't even have a separate points table - what do people think? It feels more robust to have separate tables, but I don't have much experience of database design.

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• What's a good starting point, tutorial, or project, to learn database programming?

  - by DarthNoodles

  I've been a Software Developer now for over 10 years. I've mostly worked in Embedded C with some time spent on C++ (limited) and Java. I'm looking to learn some new technologies and skills. I thought that database programming may be interesting to learn. I would like to make my own pet project in order to learn these things. My platform of choice is Windows but can work in Linux also. My ideal pet project would involve a GUI and some network/internet programming also which I have some experience doing. I wouldn't mind getting into C# but don't want to bite off more than I can chew right now as my spare time is limited. If I understand correctly SQLite allows for programs to use a database without running an ODBC server. Is this correct? Is that a good place to start? What can I do to start that is not too complicated but not so simple that I won't learn the details also? Your opinions and feedback would be appreciated.

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