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• Which MySQL Fork/Version to Pick??

  - by Drew

  As most of you know, Sun acquired MySQL (and later Oracle acquired Sun), and during these acquisitions, there were a lot of FUD in MySQL community which resulted in creation of various forks. Today we have MySQL from MySQL, Percona (XtraDB) MySQL, OurDelta MySQL, MariaDB, Drizzle to name a few. Which brings us to the source of the problem. We are in the process of upgrading our databases (hardware/software) and I would like to know which one of the forks should I go with. Each has their own set of pros/cons. We are currently using MySQL 5.0.x from MySQL/Linux on an 8-core machine. Our new hardware is a monster with 32 cores and 32GB of memory connecting to a fast NetApp Storage via FC. I would like to stick with MySQL from MySQL but I have heard horror stories on how badly MySQL 5.1 performs on many cores. I have also heard that MySQL 5.4 performs better on multi-core machines but that's still not production ready. In addition, I have also heard a lot of good things about Percona builds. This is what I know so far: MySQL 5.1 from MySQL: Reliable choice, but doesn't scale well on a big machine Percona: Scales well, good backing company. I don't have much experience with it MariaDB: Don't know much about it besides that it was founded by Original MySQL developers (including Monty) OurDelta: Don't know much Drizzle: Mostly optimized for cloud computing I would like to know what's the general notion about this problem. Which build/version should I go with? How are you guys picking your builds/versions? Thanks!

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• How to setup relationships in contact Database

  - by Walt

  I am currently embarking on a new venture to learn PHP and MySQL. I have done some simple databases in the past using Access, but this one is to be a web-centric database for tracking a myriad of data including contacts and project information. I will need to link the various tables in various relationships, and I am not sure the best way to do that. Since I am just starting out with PHP/MySQL I am researching online sources for learning as much as possible. If anyone has recommendations on books or websites, I would appreciate it. In setting up my tables, one major area that I am concerned with is contacts. I will have a variety of contacts that include: employees, clients, vendors, subcontractors, etc.. and a single contact can be multiple types and each type would have various additional fields that pertain to them. My thought was to have one contacts table that links to other tables for the various contact types. I'm not sure which field type or setup of table options are best... Thoughts? This scenario will likely play out in other areas of the database as well for projects and products. Any pointers/direction would be appreciated. WES

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• Setting up relations/mappings for a SQLAlchemy many-to-many database

  - by Brent Ramerth

  I'm new to SQLAlchemy and relational databases, and I'm trying to set up a model for an annotated lexicon. I want to support an arbitrary number of key-value annotations for the words which can be added or removed at runtime. Since there will be a lot of repetition in the names of the keys, I don't want to use this solution directly, although the code is similar. My design has word objects and property objects. The words and properties are stored in separate tables with a property_values table that links the two. Here's the code: from sqlalchemy import Column, Integer, String, Table, create_engine from sqlalchemy import MetaData, ForeignKey from sqlalchemy.orm import relation, mapper, sessionmaker from sqlalchemy.ext.declarative import declarative_base engine = create_engine('sqlite:///test.db', echo=True) meta = MetaData(bind=engine) property_values = Table('property_values', meta, Column('word_id', Integer, ForeignKey('words.id')), Column('property_id', Integer, ForeignKey('properties.id')), Column('value', String(20)) ) words = Table('words', meta, Column('id', Integer, primary_key=True), Column('name', String(20)), Column('freq', Integer) ) properties = Table('properties', meta, Column('id', Integer, primary_key=True), Column('name', String(20), nullable=False, unique=True) ) meta.create_all() class Word(object): def __init__(self, name, freq=1): self.name = name self.freq = freq class Property(object): def __init__(self, name): self.name = name mapper(Property, properties) Now I'd like to be able to do the following: Session = sessionmaker(bind=engine) s = Session() word = Word('foo', 42) word['bar'] = 'yes' # or word.bar = 'yes' ? s.add(word) s.commit() Ideally this should add 1|foo|42 to the words table, add 1|bar to the properties table, and add 1|1|yes to the property_values table. However, I don't have the right mappings and relations in place to make this happen. I get the sense from reading the documentation at http://www.sqlalchemy.org/docs/05/mappers.html#association-pattern that I want to use an association proxy or something of that sort here, but the syntax is unclear to me. I experimented with this: mapper(Word, words, properties={ 'properties': relation(Property, secondary=property_values) }) but this mapper only fills in the foreign key values, and I need to fill in the other value as well. Any assistance would be greatly appreciated.

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• Using an ORM with a database that has no defined relationships?

  - by Ahmad

  Consider a database(MSSQL 2005) that consists of 100+ tables which have primary keys defined to a certain degree. There are 'relationships' between tables, however these are not enforced with foreign key constraints. Consider the following simplified example of typical types of tables I am dealing with. The are clear relations between the User and City and Province tables. However, they key issues is the inconsistent data types in the tables and naming conventions. User: UserRowId [int] PK Name [varchar(50)] CityId [smallint] ProvinceRowId [bigint] City: CityRowId [bigint] PK CityDescription [varchar(100)] Province: ProvinceId [int] PK ProvinceDesc [varchar(50)] I am considering a rewrite of the application (in ASP.net MVC) that uses this data source as is similar in design to MVC storefront. However I am going through a proof of concept phase and this is one of the stumbling blocks I have come across. What are my options in terms of ORM choice that can be easily used and why? Should I even be considering an ORM? (The reason I ask this is that most explanations and tutorials all work with relatively cleanly designed existing databases, or newly created ones when compared to mine. I am thus having a very hard time trying to find a way forward with this problem) There is a huge amount of existing SQL queries, would a datamappper(eg IBatis.net) be more suitable since we could easily modify them to work and reuse the investment already made? I have found this question on SO which indicates to me that an ORM can be used - however I get the impression that this a question of mapping? Note: at the moment, the object model is not clearly defined as it was non-existent. The existing system pretty much did almost everything in SQL or consisted of overly complicated, and numerous queries to complete fucntionality. I am pretty much a noob and have zero experience around ORMs and MVC - so this an awesome learning curve I am on.

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• Installer for asp.net web application

  - by Thurein

  Hi I am trying to implement a installer which is going to perform following tasks.1. Check and install .net 3.52. check and install SQL server 2008 (standard edition)3. create the databases4. create a virtual directory and deploy published resources5. Deploy SSIS and package for the datawarehousing and to run the SSAS package.Right now I am using wix, to deal with some of the task, its working for me for now, but I just want to know other options and better way to do this (is there any) .Thanks and regardsThurein I am trying to implement an installer, which I m gonna hand it to the end user as a product. Check and install .net 3.5 check and install SQL server 2008 (standard edition) create the databases create a virtual directory and deploy published resources Deploy SSIS and package for the datawarehousing and to run the SSAS package. Right now I am using wix, to deal with some of the task, it works for me, but I am just curious about other options and better ways to do this (is there any) . My main intension is, I would like to distribute my product (asp.net web application) to the end user for a trial, and end user with the limited IT knowledge could install and use that web application with in a group of user. After the end of trial period the user could ask for the activation key for further usages. Thanks Thurein

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• Web development scheme for staging and production servers using Git Push

  - by ServAce85

  I am using git to manage a dynamic website (PHP + MySQL) and I want to send my files from my localhost to my staging and development servers in the most efficient and hassle-free way. I am currently convinced that the best way for me to approach this problem is to use this git branching model to organize my local git repo. From there, I will use the release branches to push to my staging server for testing. Once I am happy that the release code works on the staging server, I can then merge with my master branch and push that to my production server. Pushing to Staging Server: As noted in many introductory git posts, I could run into problems pushing into a non-bare repo, so, as suggested in this response, I plan to push the release branch to a bare repo on the server and have a post-receive hook that clones the bare repo to a non-bare repo that also acts as the web-hosted directory. Pushing to Production Server: Here's my newest source of confusion... In the response that I cited above, it made me curious as to why @Paul states that it's a completely different story when pushing to a live, development server. I guess I don't see the problem. Would it be safe and hassle-free to follow the same steps as above, but for the master branch? Where are the potential pit-falls? Config Files: With respect to configuration files that are unique to each environment (.htaccess, config.php, etc), it seems simplest to .gitignore each of those files in their respective repos on their respective servers. Can you see anything immediately wrong with this? Better solutions? Accessing Data: Finally, as I initially stated, the site uses MySQL databases to store data. How would you suggest I access that data (for testing purposes) from the staging server and localhost? I realize that I may have asked way too many questions for a single post, but since they're all related to the best way to set up this development scheme, I thought it was necessary.

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• Best approach for Java/Maven/JPA/Hibernate build with multiple database vendor support?

  - by HDave

  I have an enterprise application that uses a single database, but the application needs to support mysql, oracle, and sql*server as installation options. To try to remain portable we are using JPA annotations with Hibernate as the implementation. We also have a test-bed instance of each database running for development. The app is building nicely in Maven, and I've played around with the hibernate3-maven-plugin and can auto-generate DDL for a given database dialect. What is the best way to approach this so that individual developers can easily test against all three databases and our Hudson based CI server can build things propertly. More specifically: 1) I thought the hbm2ddl goal in the hibernate3-maven-plugin would just generate a schema file, but apparently it connects to a live database and attempts to create the schema. Is there a way to have this just create the schema file for each database dialect without connecting to a database? 2) If the hibernate3-maven-plug insists on actually creating the database schema, is there a way to have it drop the database and recreate it before creating the schema? 3) I am thinking that each developer (and the hudson build machine) should have their own separate database on each database server. Is this typical? 4) Will developers have to run Maven three times...once for each database vendor? If so, how do I merge the results on the build machine? 5) There is a hbm2doc goal within hibernate3-maven-plugin. It seems overkill to run this three times...I gotta believe it'd be nearly identical for each database.

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• multi-shop orders table and sequential order numbers based on shop

  - by imanc

  Hey, I am looking at building a shop solution that needs to be scalable. Currently it retrieves 1-2000 orders on average per day across multiple country based shops (e.g. uk, us, de, dk, es etc.) but this order could be 10x this amount in two years. I am looking at either using separate country-shop databases to store the orders tables, or looking to combine all into one order table. If all orders exist in one table with a global ID (auto num) and country ID (e.g uk,de,dk etc.), each countries orders would also need to have sequential ordering. So in essence, we'd have to have a global ID and a country order ID, with the country order ID being sequential for countries only, e.g. global ID = 1000, country = UK, country order ID = 1000 global ID = 1001, country = DE, country order ID = 1000 global ID = 1002, country = DE, country order ID = 1001 global ID = 1003, country = DE, country order ID = 1002 global ID = 1004, country = UK, country order ID = 1001 THe global ID would be DB generated and not something I would need to worry about. But I am thinking that I'd have to do a query to get the current country order based ID+1 to find the next sequential number. Two things concern me about this: 1) query times when the table has potentially millions of rows of data and I'm doing a read before a write, 2) the potential for ID number clashes due to simultaneous writes/reads. With a MyISAM table the entire table could be locked whilst the last country order + 1 is retrieved, to prevent ID number clashes. I am wondering if anyone knows of a more elegant solution? Cheers, imanc

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• Do database engines other than SQL Server behave this way?

  - by Yishai

  I have a stored procedure that goes something like this (pseudo code) storedprocedure param1, param2, param3, param4 begin if (param4 = 'Y') begin select * from SOME_VIEW order by somecolumn end else if (param1 is null) begin select * from SOME_VIEW where (param2 is null or param2 = SOME_VIEW.Somecolumn2) and (param3 is null or param3 = SOME_VIEW.SomeColumn3) order by somecolumn end else select somethingcompletelydifferent end All ran well for a long time. Suddenly, the query started running forever if param4 was 'Y'. Changing the code to this: storedprocedure param1, param2, param3, param4 begin if (param4 = 'Y') begin set param2 = null set param3 = null end if (param1 is null) begin select * from SOME_VIEW where (param2 is null or param2 = SOME_VIEW.Somecolumn2) and (param3 is null or param3 = SOME_VIEW.SomeColumn3) order by somecolumn end else select somethingcompletelydifferent And it runs again within expected parameters (15 seconds or so for 40,000+ records). This is with SQL Server 2005. The gist of my question is this particular "feature" specific to SQL Server, or is this a common feature among RDBMS' in general that: Queries that ran fine for two years just stop working as the data grows. The "new" execution plan destroys the ability of the database server to execute the query even though a logically equivalent alternative runs just fine? This may seem like a rant against SQL Server, and I suppose to some degree it is, but I really do want to know if others experience this kind of reality with Oracle, DB2 or any other RDBMS. Although I have some experience with others, I have only seen this kind of volume and complexity on SQL Server, so I'm curious if others with large complex databases have similar experience in other products.

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• Relational MySQL - fetched properties?

  - by Kelso.b

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

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• Create new or update existing entity at one go with JPA

  - by Alex R

  A have a JPA entity that has timestamp field and is distinguished by a complex identifier field. What I need is to update timestamp in an entity that has already been stored, otherwise create and store new entity with the current timestamp. As it turns out the task is not as simple as it seems from the first sight. The problem is that in concurrent environment I get nasty "Unique index or primary key violation" exception. Here's my code: // Load existing entity, if any. Entity e = entityManager.find(Entity.class, id); if (e == null) { // Could not find entity with the specified id in the database, so create new one. e = entityManager.merge(new Entity(id)); } // Set current time... e.setTimestamp(new Date()); // ...and finally save entity. entityManager.flush(); Please note that in this example entity identifier is not generated on insert, it is known in advance. When two or more of threads run this block of code in parallel, they may simultaneously get null from entityManager.find(Entity.class, id) method call, so they will attempt to save two or more entities at the same time, with the same identifier resulting in error. I think that there are few solutions to the problem. Sure I could synchronize this code block with a global lock to prevent concurrent access to the database, but would it be the most efficient way? Some databases support very handy MERGE statement that updates existing or creates new row if none exists. But I doubt that OpenJPA (JPA implementation of my choice) supports it. Event if JPA does not support SQL MERGE, I can always fall back to plain old JDBC and do whatever I want with the database. But I don't want to leave comfortable API and mess with hairy JDBC+SQL combination. There is a magic trick to fix it using standard JPA API only, but I don't know it yet. Please help.

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• MySQLPython is ignoring my my.cnf file. Where does it get its information?

  - by ?????

  When I try to use MySQLPython (via SQLAlchemy) I get the error File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/MySQL_python-1.2.3c1-py2.6-macosx-10.6-x86_64.egg/MySQLdb/connections.py", line 188, in __init__ super(Connection, self).__init__(*args, **kwargs2) sqlalchemy.exc.OperationalError: (OperationalError) (2002, "Can't connect to local MySQL server through socket '/opt/local/var/run/mysql5/mysqld.sock' (2)") None None but no other mysql client on my machine sees it fine! My my.cnf file states: [client] port = 3306 socket = /tmp/mysql/mysql.sock [safe_mysqld] socket = /tmp/mysql/mysql.sock [mysqld_safe] socket = /tmp/mysql/mysql.sock [mysqld] socket = /tmp/mysql/mysql.sock port = 3306 and the mysql.sock file is, indeed, located in /tmp/mysql I verified that ~/.my.cnf and /var/lib/mysql/my.cnf aren't overriding it. The mysql5 client program, etc, has no trouble connecting and neither does a groovy/grails installation on the same machine using jdbc/mysql connection thrilllap-2:~ swirsky$ mysql5 Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 6 Server version: 5.1.47 Source distribution Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved. This software comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to modify and redistribute it under the GPL v2 license Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | test | +--------------------+ 2 rows in set (0.00 sec) mysql> Why can't MySQLdb for python figure this out? Where would it look if not the my.cnf files?

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• Looking to reimplement build toolchain from bash/grep/sed/awk/(auto)make/configure to something more

  - by wash

  I currently maintain a few boxes that house a loosely related cornucopia of coding projects, databases and repositories (ranging from a homebrew *nix distro to my class notes), maintained by myself and a few equally pasty-skinned nerdy friends (all of said cornucopia is stored in SVN). The vast majority of our code is in C/C++/assembly (a few utilities are in python/perl/php, we're not big java fans), compiled in gcc. Our build toolchain typically consists of a hodgepodge of make, bash, grep, sed and awk. Recent discovery of a Makefile nearly as long as the program it builds (as well as everyone's general anxiety with my cryptic sed and awking) has motivated me to seek a less painful build system. Currently, the strongest candidate I've come across is Boost Build/Bjam as a replacement for GNU make and python as a replacement for our build-related bash scripts. Are there any other C/C++/asm build systems out there worth looking into? I've browsed through a number of make alternatives, but I haven't found any that are developed by names I know aside from Boost's. (I should note that an ability to easily extract information from svn commandline tools such as svnversion is important, as well as enough flexibility to configure for builds of asm projects as easily as c/c++ projects)

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• Building out a well-structured service layer

  - by Chris Stewart

  First, I want to say that it has been awhile since I've gotten into the kind of detail I am at currently. Lately, I've been very much in the SharePoint world and my entire thought process was focused there for quite some time. I'm very glad to be creating databases again, writing "lower level" code to deal with data access, and so forth. I'm working on a very simple web application and taking the opportunity to reacquaint myself with the way I used to structure my projects and various layers of code. For instance, I might have created something like this the last time I went about building something basic from scratch: - MyProject/ -- Domain/ --- Impl/ ---- Person -- Model/ --- IPersonRepository --- Impl/ ---- PersonRepository : IPersonRepository -- Services --- IPersonService --- Impl/ ---- PersonService : IPersonService That would have been the project I did the real work in, and then referenced in the ASP.NET project. My approach was very much inspired by what I saw from the CodeCampServer project as at that time ASP.NET MVC was still very new and it was the only open project I could find actively being developed, and by solid people at that. What ways are you going about structuring your projects and code, when it comes to a general problem you're working on? Certainly various problems can put constraints on this, but assume it's a basic problem without specific needs that affect the structure and layout of your code.

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• Question about the benefit of using an ORM

  - by johnny

  I want to use an ORM for learning purposes and am try nhibernate. I am using the tutorial and then I have a real project. I can go the "old way" or use an ORM. I'm not sure I totally understand the benefit. On the one hand I can create my abstractions in code such that I can change my databases and be database independent. On the other it seems that if I actually change the database columns I have to change all my code. Why wouldn't I have my application without the ORM, change my database and change my code, instead of changing my database, orm, and code? Is it that they database structure doesn't change that much? I believe there are real benefits because ORMs are used by so many. I'm just not sure I get it yet. Thank you. EDIT: In the tutorial they have many files that are used to make the ORM work http://www.hibernate.org/362.html In the event of an application change, it seems like a lot of extra work just to say that I have "proper" abstraction layers. Because I'm new at it it doesn't look that easy to maintain and again seems like extra work, not less.

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• MySQL Stored Procedures : Use a variable as the database name in a cursor declaration

  - by Justin

  I need to use a variable to indicate what database to query in the declaration of a cursor. Here is a short snippet of the code : CREATE PROCEDURE `update_cdrs_lnp_data`(IN dbName VARCHAR(25), OUT returnCode SMALLINT) cdr_records:BEGIN DECLARE cdr_record_cursor CURSOR FOR SELECT cdrs_id, called, calling FROM dbName.cdrs WHERE lrn_checked = 'N'; # Setup logging DECLARE EXIT HANDLER FOR SQLEXCEPTION BEGIN #call log_debug('Got exception in update_cdrs_lnp_data'); SET returnCode = -1; END; As you can see, I'm TRYING to use the variable dbName to indicate in which database the query should occur within. However, MySQL will NOT allow that. I also tried things such as : CREATE PROCEDURE `update_cdrs_lnp_data`(IN dbName VARCHAR(25), OUT returnCode SMALLINT) cdr_records:BEGIN DECLARE cdr_record_cursor CURSOR FOR SET @query = CONCAT("SELECT cdrs_id, called, calling FROM " ,dbName, ".cdrs WHERE lrn_checked = 'N' "); PREPARE STMT FROM @query; EXECUTE STMT; # Setup logging DECLARE EXIT HANDLER FOR SQLEXCEPTION BEGIN #call log_debug('Got exception in update_cdrs_lnp_data'); SET returnCode = -1; END; Of course this doesn't work either as MySQL only allows a standard SQL statement in the cursor declaration. Can anyone think of a way to use the same stored procedure in multiple databases by passing in the name of the db that should be affected?

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• Guid Primary /Foreign Key dilemma SQL Server

  - by Xience

  Hi guys, I am faced with the dilemma of changing my primary keys from int identities to Guid. I'll put my problem straight up. It's a typical Retail management app, with POS and back office functionality. Has about 100 tables. The database synchronizes with other databases and receives/ sends new data. Most tables don't have frequent inserts, updates or select statements executing on them. However, some do have frequent inserts and selects on them, eg. products and orders tables. Some tables have upto 4 foreign keys in them. If i changed my primary keys from 'int' to 'Guid', would there be a performance issue when inserting or querying data from tables that have many foreign keys. I know people have said that indexes will be fragmented and 16 bytes is an issue. Space wouldn't be an issue in my case and apparently index fragmentation can also be taken care of using 'NEWSEQUENTIALID()' function. Can someone tell me, from there experience, if Guid will be problematic in tables with many foreign keys. I'll be much appreciative of your thoughts on it...

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• PHP code displayed in browser

  - by Drake

  so, I'm working on a databases project, and i'm trying to code incrementally. the problem is, when i go to test the php in browser, it displays the php code after my use of "-". the html printing is displayed properly, which is AFTER the point where the - is. here is the php: <?php function getGraphicNovel(){ include_once("./connect.php"); $db_connection = new mysqli($SERVER, $USERNAME, $PASSWORD, $DATABASE); if (mysqli_connect_errno()) { echo("Can't connect to MySQL Server. Error code: " . mysqli_connect_error()); return null; } $stmt = $db_connection->stmt_init(); $returnValue = "invalid"; if($stmt.prepare("select series from graphic_novel_main natural join graphic_novel_misc")) { $stmt->execute(); $stmt->bind_result($series); while ($stmt->fetch()) { echo "<tr><td>" . $series . "</td></tr>"; } $stmt->close(); } $db_connection->close(); } getGraphicNovel(); ?> here is a link to the page. hopefully it works for people outside the school's network. http://plato.cs.virginia.edu/~paw5k/cainedb/viewall.html if anyone knows why this is happening, your input would be great!

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• Making a database backup to SDCard on Android

  - by Pentium10

  I am using the below code to write a backup copy to SDCard and I get java.io.IOException: Parent directory of file is not writable: /sdcard/mydbfile.db private class ExportDatabaseFileTask extends AsyncTask<String, Void, Boolean> { private final ProgressDialog dialog = new ProgressDialog(ctx); // can use UI thread here protected void onPreExecute() { this.dialog.setMessage("Exporting database..."); this.dialog.show(); } // automatically done on worker thread (separate from UI thread) protected Boolean doInBackground(final String... args) { File dbFile = new File(Environment.getDataDirectory() + "/data/com.mypkg/databases/mydbfile.db"); File exportDir = new File(Environment.getExternalStorageDirectory(), ""); if (!exportDir.exists()) { exportDir.mkdirs(); } File file = new File(exportDir, dbFile.getName()); try { file.createNewFile(); this.copyFile(dbFile, file); return true; } catch (IOException e) { Log.e("mypck", e.getMessage(), e); return false; } } // can use UI thread here protected void onPostExecute(final Boolean success) { if (this.dialog.isShowing()) { this.dialog.dismiss(); } if (success) { Toast.makeText(ctx, "Export successful!", Toast.LENGTH_SHORT).show(); } else { Toast.makeText(ctx, "Export failed", Toast.LENGTH_SHORT).show(); } } void copyFile(File src, File dst) throws IOException { FileChannel inChannel = new FileInputStream(src).getChannel(); FileChannel outChannel = new FileOutputStream(dst).getChannel(); try { inChannel.transferTo(0, inChannel.size(), outChannel); } finally { if (inChannel != null) inChannel.close(); if (outChannel != null) outChannel.close(); } } }

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• Way to store a large dictionary with low memory footprint + fast lookups (on Android)

  - by BobbyJim

  I'm developing an android word game app that needs a large (~250,000 word dictionary) available. I need: reasonably fast look ups e.g. constant time preferable, need to do maybe 200 lookups a second on occasion to solve a word puzzle and maybe 20 lookups within 0.2 second more often to check words the user just spelled. EDIT: Lookups are typically asking "Is in the dictionary?". I'd like to support up to two wildcards in the word as well, but this is easy enough by just generating all possible letters the wildcards could have been and checking the generated words (i.e. 26 * 26 lookups for a word with two wildcards). as it's a mobile app, using as little memory as possible and requiring only a small initial download for the dictionary data is top priority. My first naive attempts used Java's HashMap class, which caused an out of memory exception. I've looked into using the SQL lite databases available on android, but this seems like overkill. What's a good way to do what I need?

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• How do people handle foreign keys on clients when synchronizing to master db

  - by excsm

  Hi, I'm writing an application with offline support. i.e. browser/mobile clients sync commands to the master db every so often. I'm using uuid's on both client and server-side. When synching up to the server, the servre will return a map of local uuids (luid) to server uuids (suid). Upon receiving this map, clients updated their records suid attributes with the appropriate values. However, say a client record, e.g. a todo, has an attribute 'list_id' which holds the foreign key to the todos' list record. I use luids in foreign_keys on clients. However, when that attribute is sent over to the server, it would dirty the server db with luids rather than the suid the server is using. My current solution, is for the master server to keep a record of the mappings of luids to suids (per client id) and for each foreign key in a command, look up the suid for that particular client and use the suid instead. I'm wondering wether others have come across thus problem and if so how they have solved it? Is there a more efficient, simpler way? I took a look at this question "Synchronizing one or more databases with a master database - Foreign keys (5)" and someone seemed to suggest my current solution as one option, composite keys using suids and autoincrementing sequences and another option using -ve ids for client ids and then updating all negative ids with the suids. Both of these other options seem like a lot more work. Thanks, Saimon

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• MySQL " identify storage engine statement"

  - by sammysmall

  This IS NOT a Homework question! While building my current student database project I realized that I may want to identify comprehensive information about a database design in the future. More-so if I am fortunate enough to get a job in this field and were handed a database project how could I break down certain elements for identification... In all of my previous designs I have been using MySQL Community Server (GPL) 5.1.42, I thought (duh) that I was using the MyISAM based on most of my text-book instruction and MySQL 5.0 Reference Manual :: 13 Storage Engines :: 13.1 The MyISAM Storage Engine I determined that this was in fact incorrect for this version and the use of "SHOW ENGINES" at the console... No problem, figured out why they have "versions" the need to pay attention to what version is being used, and the need for a means to determine what I am about to mess up "if" I do not pay attention to detail... Q1. Specifically what statement will identify the version used by someone elses initial database creation? (since I created my own databases I know what version I used) Q2. Specifically what statement will identify the storage engine that the developer used when creating the database. (I specified a particular database in my collection then tried SHOW Engine, did not work, then tried to just get the metadata from one table in that database: mysql SELECT duck_cust, table_type, engine - FROM INFORMATION_SCHEMA.tables - WHERE table_schema = 'tp' - ORDER BY table_type ASC, table_name DESC; as this was not really what I wanted (and did not work) I am looking for some direction from the pros... Q3. (If you really have the inclination to continue helping) If I were to access a database from an earlier/later "version" are there backward/forward compatibility issues for maintaining/updating data between versions? Please and Thank you in advance for your time and efforts! sammysmall

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• Architecture for database analytics

  - by David Cournapeau

  Hi, We have an architecture where we provide each customer Business Intelligence-like services for their website (internet merchant). Now, I need to analyze those data internally (for algorithmic improvement, performance tracking, etc...) and those are potentially quite heavy: we have up to millions of rows / customer / day, and I may want to know how many queries we had in the last month, weekly compared, etc... that is the order of billions entries if not more. The way it is currently done is quite standard: daily scripts which scan the databases, and generate big CSV files. I don't like this solutions for several reasons: as typical with those kinds of scripts, they fall into the write-once and never-touched-again category tracking things in "real-time" is necessary (we have separate toolset to query the last few hours ATM). this is slow and non-"agile" Although I have some experience in dealing with huge datasets for scientific usage, I am a complete beginner as far as traditional RDBM go. It seems that using column-oriented database for analytics could be a solution (the analytics don't need most of the data we have in the app database), but I would like to know what other options are available for this kind of issues.

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• Just 2 free months 2 learn or improve my skills

  - by microspino

  On the 30 of June I will leave my every day work to start as freelance developer. I'd like to set a period of 2 months apart to improve my dev skills. At work I code in C# and during my spare time I enjoyed building Ruby on Rails web applications and creating some Arduino prototypes. I'm something more than junior but I don't feel really a senior developer because I never had a big corporate project built and designed by me with help of other juniors (although I don't think this is really a good definiton of a "senior", It helps describing my feelings). Using a scale from 0 (ignorant) to 10 (proficient like a "samurai") the list below describes my skills that I would like to improve with just 2 months. I've already bought some nice and updated books on all the subjects hereunder: The order doesn't matter C = 1 C# & .Net = 6 Arduino & Processing = 2 Ruby = 5 Rails = 5 HTML/XHTML/CSS = 9 Javascript = 6 Objective-C/iPhone dev = 2 Python = 4 Django = 4 Desing Patterns = 3 Algorythms = 3 Git = 5 I haven't included SQL or Databases in general nor Networking because I spent 10 years working in the past with them and I feel pretty solid for now. As an aside, I've made up some interest in Redis, Node.js, HTML5 reading about them on the web. After two months, since I have to pay my bills, I could go searching for some new job. If learning and developing were really good maybe I could also invest on something I gave birth during them. Can You give me some piece of advice on which you think It's better to improve or develop a learning project on (something like a "summer of code" thing)? The all point Is to see my weeknesses and work on them.

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• How would you start automating my job?

  - by Jurily

  At my new job, we sell imported stuff. In order to be able to sell said stuff, currently the following things need to happen for every incoming shipment: Invoice arrives, in the form of an email attachment, Excel spreadsheet Monkey opens invoice, copy-pastes the relevant part of three columns into the relevant parts of a spreadsheet template, where extremely complex calculations happen, like =B2*550 Monkey sends this new spreadsheet to boss (email if lucky, printer otherwise), who sets the retail price Monkey opens the reply, then proceeds to input the data into the production database using a client program that is unusable on so many levels it's not even worth detailing Monkey fires up HyperTerminal, types in "AT", disconnect Monkey sends text messages and emails to customers using another part of the horrible client program, one at a time I want to change Monkey from myself to software wherever possible. I've never written anything that interfaces with email, Excel, databases or SMS before, but I'd be more than happy to learn if it saves me from this. Here's my uneducated wishlist: Monkey asks Thunderbird (mail server perhaps?) for the attachment Monkey tells Excel to dump the spreadsheet into a more Jurily-friendly format, like CSV or something Monkey parses the output, does the complex calculations // TODO: find a way to get the boss-generated prices with minimal manual labor involved Monkey connects to the database, inserts data Monkey spams costumers Is all this feasible? If yes, where do I start reading? How would you improve it? What language/framework do you think would be ideal for this? What would you do about the boss?

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