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• emca fails with "Database instance is unavailable" though available

  - by Giri Mandalika

  The following example shows the symptoms of failure, and the exact error message. $ emca -repos create ... Password for SYSMAN user: Do you wish to continue? [yes(Y)/no(N)]: Y Nov 19, 2012 10:33:42 AM oracle.sysman.emcp.DatabaseChecks \ checkDbAvailabilityImpl WARNING: ORA-01034: ORACLE not available Nov 19, 2012 10:33:42 AM oracle.sysman.emcp.DatabaseChecks \ throwDBUnavailableException SEVERE: Database instance is unavailable. Fix the ORA error thrown and run EM Configuration Assistant again. Some of the possible reasons may be : 1) Database may not be up. 2) Database is started setting environment variable ORACLE_HOME with trailing '/'. Reset ORACLE_HOME and bounce the database. For eg. Database is started setting environment variable ORACLE_HOME=/scratch/db/ . Reset ORACLE_HOME=/scratch/db and bounce the database. Fix: Ensure that the ORACLE_HOME is pointing to the right location in $ORACLE_HOME/bin/emca file. Rather than installing from scratch, if ORACLE_HOME was copied over from another location, likely it results in wrong location for ORACLE_HOME in several Enterprise Manager (EM) specific scripts and files. It usually happens when the directory structure on the target machine is not identical to the structure on the original/source machine, including the top level directory location where Oracle RDBMS was installed properly using the installer.

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• Grid Infrastructure Management Repository (GIMR) database now mandatory in Oracle GI 12.1.0.2

  - by Mike Dietrich

  During the installation of Oracle Grid Infrastructure 12.1.0.1 you've had the following option to choose YES/NO to install the Grid Infrastructure Management Repository (GIMR) database MGMTDB: With Oracle Grid Infrastructure 12.1.0.2 this choice has become obsolete and the above screen does not appear anymore. The GIMR database has become mandatory.  What gets stored in the GIMR? See the documentation here See the changes in Oracle Clusterware 12.1.0.2 here: Automatic Installation of Grid Infrastructure Management Repository The Grid Infrastructure Management Repository is automatically installed with Oracle Grid Infrastructure 12c release 1 (12.1.0.2). The Grid Infrastructure Management Repository enables such features as Cluster Health Monitor, Oracle Database QoS Management, and Rapid Home Provisioning, and provides a historical metric repository that simplifies viewing of past performance and diagnosis of issues. This capability is fully integrated into Oracle Enterprise Manager Cloud Control for seamless management. Furthermore what the doc doesn't say explicitly: The -MGMTDB has now become a single-tenant deployment having a CDB with one PDB This will allow the use of a Utility Cluster that can hold the CDB for a collection of GIMR PDBs When you've had already an Oracle 12.1.0.1 GIMR this database will be destroyed and recreated Preserving the CHM/OS data can be acchieved with OCULMON to dump it out into node view The data files associated with it will be created within the same disk group as OCR and VOTING  In a future release there may be an option offered to put in into a separate disk group Some important MOS Notes: MOS Note 1568402.1FAQ: 12c Grid Infrastructure Management Repository, states there's no supported procedure to enable Management Database once the GI stack is configured MOS Note 1589394.1How to Move GI Management Repository to Different Shared Storage(shows how to delete and recreate the MGMTDB) MOS Note 1631336.1Cannot delete Management Database (MGMTDB) in 12.1 -Mike

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• Remote Access to MSSQL Database From 1&1 Hosting [duplicate]

  - by Zerkey

  This question already has an answer here: How to find web hosting that meets my requirements? 5 answers I just paid ($6 /month) for shared Windows hosting through 1&1 hosting. I was having trouble connecting to my database from home, so I sent an email to support. I received the following response: As we checked your concern here in our end, please be advised that due to limitation of Shared Hosting services, there is no option to connect the database to your SQL Management Studio or through Visual Studio. It is only possible for Dedicated Server package. You may only access the database using MyLittleAdmin at the Control Panel. A dedicated server is like $200 per month! What is the point of having database access only through a web console? I feel I am missing something here, or maybe the support agent is. Is there a way to access my MS SQL database on their servers through Visual Studio or SQL Management Studio from my machine? If not, is there a web host who allows this for less than $200 a month? EDIT: Marked as duplicate... I'm not asking for a list of web hosts, I'm asking how to remotely connect to my MSSQL database through 1&1's services.

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• SQL SERVER – Validating Unique Columnname Across Whole Database

  - by pinaldave

  I sometimes come across very strange requirements and often I do not receive a proper explanation of the same. Here is the one of those examples. Asker: “Our business requirement is when we add new column we want it unique across current database.” Pinal: “Why do you have such requirement?” Asker: “Do you know the solution?” Pinal: “Sure I can come up with the answer but it will help me to come up with an optimal answer if I know the business need.” Asker: “Thanks – what will be the answer in that case.” Pinal: “Honestly I am just curious about the reason why you need your column name to be unique across database.” (Silence) Pinal: “Alright – here is the answer – I guess you do not want to tell me reason.” Option 1: Check if Column Exists in Current Database IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn') BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END Option 2: Check if Column Exists in Current Database in Specific Table IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn' AND OBJECT_ID = OBJECT_ID(N'tableName')) BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END I guess user did not want to share the reason why he had a unique requirement of having column name unique across databases. Here is my question back to you – have you faced a similar situation ever where you needed unique column name across a database. If not, can you guess what could be the reason for this kind of requirement?  Additional Reference: SQL SERVER – Query to Find Column From All Tables of Database Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL System Table, SQL Tips and Tricks, T SQL, Technology

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• Migration a database from 32bit to 64bit

  - by Mike Dietrich

  Database migrations from an 32bit environment to an 64bit environment keeping the same platform architecture (e.g. moving an Oracle 10.2.0.5 database from MS Windows XP 32bit to MS Windows Server 2003 64bit) does not happen that often anymore. But still we see them getting done. And there are a few things to note when doing such a move. First of all the important question is:Will you upgrade your database as part of this move - Yes or No? If you say "Yes" then you are almost done with that topic as we will take care of that bitnes move during the upgrade. The only thing you have to take care is OLAP in case you are using OLAP Option with Analytic Workspaces (AW) by yourself. Those store data in Binary LOBs - and in order to move AWs from 32bit to 64bit you have to export your AWs prior to the move - and import them later on. People who don't use OLAP don't have to take care on this. But if you say "No" (meaning: no upgrade actions involved - you keep your database version) then you have to make sure to invalidate all packages and stored code in the database before you shutdown your database in the 32bit environment and prior to moving it over. And the same rule as above for OLAP applies once you use the OLAP Option. In the source environment: startup upgrade;    -- [or startup migrate; -- for Oracle 9i] @?/rdbms/admin/utlirp.sqlshutdown immediate In the destination environment: startup upgrade @?/olap/admin/xumuts.plb --Only if OLAP Option is installed@?/rdbms/admin/utlrp.sql The script utlirp.sql will invalidate all packages and stored code, utlrp.sql will recompile - and xumuts.plb will rebuild the OLAP Analytic Workspaces in case you have the OLAP Option installed.

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• Storing info in a PostgreSQl database issue

  - by MrEnder

  Ok I am making a registry for my website. First page asks for some personal info if($error==false) { $query = pg_query("INSERT INTO chatterlogins(firstName, lastName, gender, password, ageMonth, ageDay, ageYear, email, createDate) VALUES('$firstNameSignup', '$lastNameSignup', '$genderSignup', md5('$passwordSignup'), $monthSignup, $daySignup, $yearSignup, '$emailSignup', now());"); $query = pg_query("INSERT INTO chatterprofileinfo(email, lastLogin) VALUES('$emailSignup', now());"); $userNameSet = $emailSignup; $_SESSION['$userNameSet'] = $userNameSet; header('Location: signup_step2.php'.$rdruri); } The first query works. The second query works but doesn't save the email... the session doesn't work but the header works and sends me to the next page I get no errors even if I comment out header next page @session_start(); $conn = pg_connect("host=localhost dbname=brittains_db user=brittains password=XXXX" ); $signinCheck = false; $checkForm = ""; if(isset($_SESSION['$userName'])) { $userName = $_SESSION['$userName']; $signinCheck = true; $query = pg_query("UPDATE chatterprofileinfo SET lastLogin='now()' WHERE email='$userName'"); } if(isset($_SESSION['$userNameSet'])) { $userName = $_SESSION['$userNameSet']; $signinCheck = true; $query = pg_query("UPDATE chatterprofileinfo SET lastLogin='now()' WHERE email='$userName'"); } This is the top starting the session depending on if your logged in or not. then if I enter in the info here and put it through this if($error==false) { $query = pg_query("UPDATE chatterprofileinfo SET aboutSelf='$aboutSelf', hobbies='$hobbies', music='$music', tv='$tv', sports='$sports', lastLogin='now()' WHERE email='$userName'") or exit(pg_last_error()); //header('Location: signup_step3.php'.$rdruri); } nothing shows up for on my database from this. I have no idea where I went wrong the website is http://opentech.durhamcollege.ca/~intn2201/brittains/chatter/

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• The Date type and the Android database

  - by cdonner

  I understand that SQLite stores dates as long integers. When I read rows into a cursor using the standard method (i.e. using the query() method that reads data into a cursor), the result is a date string that includes the time. If I want a different format, I have to parse the string back into a date - possible, but a bit backwards. By using a ViewBinder (as suggested in this question), I can pretty much do anything I want, but the date is already a string at the time the method executes. The accepted answer to the above question also suggests that storing dates as longs would help avoid this problem. I don't want to do that, just in case I want to interpret my data with something else than this application. Maybe I want to expose it via a provider. Is there a way to handle this in the database adapter instead, i.e. controlling the date format that the cursor contains, so that I don't have to change the schema, and don't have to parse the default output back into a Date type?

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• Is Berkeley DB XML a viable database backend?

  - by w00t

  Apparently, BDB-XML has been around since at least 2003 but I only recently stumbled upon it on Oracle's website: Berkeley DB XML. Here's the blurb: Oracle Berkeley DB XML is an open source, embeddable XML database with XQuery-based access to documents stored in containers and indexed based on their content. Oracle Berkeley DB XML is built on top of Oracle Berkeley DB and inherits its rich features and attributes. Like Oracle Berkeley DB, it runs in process with the application with no need for human administration. Oracle Berkeley DB XML adds a document parser, XML indexer and XQuery engine on top of Oracle Berkeley DB to enable the fastest, most efficient retrieval of data. To me it seems that the underlying ideas are technically sound and probably more mature than the newer document-based DBs like CouchDB or MongoDB. It has support for C, C++, Ruby and Perl, as far as I can determine. It even has HA-capabilities like automatic replication using a master/slave model with automatic election. However, I can't seem to find any projects that use it. Is there something fundamentally wrong with it? Is the license too onerous? Is it too complicated? Why is it not being used?

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• Guice, JDBC and managing database connections

  - by pledge

  I'm looking to create a sample project while learning Guice which uses JDBC to read/write to a SQL database. However, after years of using Spring and letting it abstract away connection handling and transactions I'm struggling to work it our conceptually. I'd like to have a service which starts and stops a transaction and calls numerous repositories which reuse the same connection and participate in the same transaction. My questions are: Where do I create my Datasource? How do I give the repositories access to the connection? (ThreadLocal?) Best way to manage the transaction (Creating an Interceptor for an annotation?) The code below shows how I would do this in Spring. The JdbcOperations injected into each repository would have access to the connection associated with the active transaction. I haven't been able to find many tutorials which cover this, beyond ones which show creating interceptors for transactions. I am happy with continuing to use Spring as it is working very well in my projects, but I'd like to know how to do this in pure Guice and JBBC (No JPA/Hibernate/Warp/Reusing Spring) @Service public class MyService implements MyInterface { @Autowired private RepositoryA repositoryA; @Autowired private RepositoryB repositoryB; @Autowired private RepositoryC repositoryC; @Override @Transactional public void doSomeWork() { this.repositoryA.someInsert(); this.repositoryB.someUpdate(); this.repositoryC.someSelect(); } } @Repository public class MyRepositoryA implements RepositoryA { @Autowired private JdbcOperations jdbcOperations; @Override public void someInsert() { //use jdbcOperations to perform an insert } } @Repository public class MyRepositoryB implements RepositoryB { @Autowired private JdbcOperations jdbcOperations; @Override public void someUpdate() { //use jdbcOperations to perform an update } } @Repository public class MyRepositoryC implements RepositoryC { @Autowired private JdbcOperations jdbcOperations; @Override public String someSelect() { //use jdbcOperations to perform a select and use a RowMapper to produce results return "select result"; } }

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• NHibernate Legacy Database Mappings Impossible?

  - by Corey Coogan

  I'm hoping someone can help me with mapping a legacy database. The problem I'm describing here has plagued others, yet I was unable to find a real good solution around the web. DISCLAIMER: this is a legacy DB. I have no control over the composite keys. They suck and can't be changed no matter much you tell me they suck. I have 2 tables, both with composite keys. One of the keys from one table is used as part of the key to get a collection from the other table. In short, the keys don't fully match between the table. ClassB is used everywhere I would like to avoid adding properties for the sake of this mapping if possible. public class ClassA { //[PK] public string SsoUid; //[PK] public string PolicyNumber; public IList<ClassB> Others; //more properties.... } public class ClassB { //[PK] public string PolicyNumber; //[PK] public string PolicyDateTime; //more properties } I want to get an instance of ClassA and get all ClassB rows that match PolicyNumber. I am trying to get something going with a one-to-many, but I realize that this may technically be a many-to-many that I am just treating as one-to-many. I've tried using an association class but didn't get far enough to see if it works. I'm new to these more complex mappings and am looking for advice. I'm open to pretty much any ideas. Thanks, Corey

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• Using Oracle hint "FIRST_ROWS" to improve Oracle database performances

  - by bobetko

  I have a statement that runs on Oracle database server. The statement has about 5 joins and there is nothing unusual there. It looks pretty much like below: SELECT field1, field2, field3, ... FROM table1, table2, table3, table4, table5 WHERE table1.id = table2.id AND table2.id = table3.id AND ... table5.userid = 1 The problem (and what is interesting) is that statement for userid = 1 takes 1 second to return 590 records. Statement for userid = 2 takes around 30 seconds to return 70 records. I don't understand why is difference so big. It seems that different execution plan is chosen for statement with userid = 1 and different for userid = 2. After I implemented Oracle Hint FIRST_ROW, performance become significantly better. Both statements (for both ids 1 and 2) produce return in under 1 second. SELECT /*+ FIRST_ROWS */ field1, field2, field3, ... FROM table1, table2, table3, table4, table5 WHERE table1.id = table2.id AND table2.id = table3.id AND ... table5.userid = 1 Questions: 1) What are possible reasons for bad performance when userid = 2 (when hint is not used)? 2) Why would execution plan be different for one vs another statement (when hint is not used)? 3) Is there anything that I should be careful about when deciding to add this hint to my queries? Thanks

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• Non-Relational Database Design

  - by Ian Varley

  I'm interested in hearing about design strategies you have used with non-relational "nosql" databases - that is, the (mostly new) class of data stores that don't use traditional relational design or SQL (such as Hypertable, CouchDB, SimpleDB, Google App Engine datastore, Voldemort, Cassandra, SQL Data Services, etc.). They're also often referred to as "key/value stores", and at base they act like giant distributed persistent hash tables. Specifically, I want to learn about the differences in conceptual data design with these new databases. What's easier, what's harder, what can't be done at all? Have you come up with alternate designs that work much better in the non-relational world? Have you hit your head against anything that seems impossible? Have you bridged the gap with any design patterns, e.g. to translate from one to the other? Do you even do explicit data models at all now (e.g. in UML) or have you chucked them entirely in favor of semi-structured / document-oriented data blobs? Do you miss any of the major extra services that RDBMSes provide, like relational integrity, arbitrarily complex transaction support, triggers, etc? I come from a SQL relational DB background, so normalization is in my blood. That said, I get the advantages of non-relational databases for simplicity and scaling, and my gut tells me that there has to be a richer overlap of design capabilities. What have you done? FYI, there have been StackOverflow discussions on similar topics here: the next generation of databases changing schemas to work with Google App Engine choosing a document-oriented database

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• GAE python database object design for simple list of values

  - by Joey

  I'm really new to database object design so please forgive any weirdness in my question. Basically, I am use Google AppEngine (Python) and contructing an object to track user info. One of these pieces of data is 40 Achievement scores. Do I make a list of ints in the User object for this? Or do I make a separate entity with my user id, the achievement index (0-39) and the score and then do a query to grab these 40 items every time I want to get the user data in total? The latter approach seems more object oriented to me, and certainly better if I extend it to have more than just scores for these 40 achievements. However, considering that I might not extend it, should I even consider just doing a simple list of 40 ints in my user data? I would then forgo doing a query, getting the sorted list of achievements, reading the score from each one just to process a response etc. Is doing this latter approach just such a common practice and hand-waved as not even worth batting an eyelash at in terms of thinking it might be more costly or complex processing wise?

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• SEO on a Database Driven Website

  - by Ryan Giglio

  I have a question about a site I'm developing. It is a database driven directory site where people can make a profile and list themselves in one or many area codes and in one or many fields of work. When someone is looking for a person to hire, they enter one or more area codes to look in (or select them with checkboxes) and when the form submits, it saves these as a cookie so the site remembers what location you were searching in. You then narrow down your search by category and field (which are links) and get a listing of all the profiles that match your search. What I am concerned about is this: because a search engine can't type in or select area codes to search in, how is it going to find and index any of the profile pages? It doesn't allow the user to search for people without first selecting an area code, because there's no practical purpose to do so. There would also be no practical purpose from a user experience/usability standpoint of simply having a list of each area code as a link to the categories page, but as far as I know, isn't that the only way for search engines to see every person? How does a site like Facebook accomplish this? There isn't some sort of master directory with a link to ever single Facebook user's profile page, and yet they're often the #1 search result for a person's name.

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• How to create database records for a financial year

  - by David A Gibson

  Hello, I need to create entities (specifically contracts) in a database table that are associated with a financial year. These contracts will be applied to projects. Any contract variation will be recorded by creating a new contract record for the same financial year but the original will remain associated with the project as a history. The projects can last several years and so at any one time a project will have a live contract record for each year as well as any number of historic contracts for that year. All of which is incidental but I'm trying to provide some context. If the contracts where for the year - it would be easy and I'd just store the Year either as a date field with the 1st of January or just an Integer. However the contracts run for financial years and I don't know how to approach this. I don't want a separate table containing the financial years as I don't want the users to have to maintain this. I don't want to store the financial year as a string "2009/2010" as this is not ideal for sorting/extracting the data. Any ideas will be helpful, my best so far is to have starting and ending year in 2 columns and just "KNOW" that starting is April of the year etc Thanks

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• Movies recommendation engine conceptual database design

  - by Supyxy

  I am working at an movie recommendations engine and i'm facing a DB design issue. My actual database looks like this: MOVIES [ID,TITLE] KEYWORDS_TABLE [ID,KEY_ID] - where ID is Foreign Key for MOVIES.id and KEY_ID is a key for a text keywords table This is not the entire DB, but i showed here what's important for my problem. I have about 50,000 movies and about 1,3 milion keywords correlations, and basically my algorithm consists in extracting all the who have the same keywords with a given movie, then ordering them by the number of keywords correlations. For example i looked for a movie similar to 'Cast away' and it returned 'Six days and six nights' because it had the most keywords correlations (4 keywords): Island Airplane crash Stranded Pilot The algorithm is based on more factors, but this one is the most important and the most difficult for the approach. Basically what i do now is getting all the movies that have at least one keyword similar to the given movie and then ordering them by other factors which are not important for a moment. There wouldn't be any problem if there weren't so many records, a query lasts in many cases up to 10-20 seconds and some of them return even over 5000 movies. Someone already helped me on here (thanks Mark Byers) with optimizing the query but that's not enough because it takes too longer SELECT DISTINCT M.title FROM keywords_table K1 JOIN keywords_table K2 ON K2.key_id = K1.key_id JOIN movies M ON K2.id = M.id WHERE K1.id = 4 So i thought it would be better if i pre-made those lists with movies recommendations for each movie, but i'm not sure how to design the tables.. whatever is it a good idea or how would you take this approach?

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• Best practices for managing updating a database with a complex set of changes

  - by Sarge

  I am writing an application where I have some publicly available information in a database which I want the users to be able to edit. The information is not textual like a wiki but is similar in concept because the edits bring the public information increasingly closer to the truth. The changes will affect multiple tables and the update needs to be automatically checked before affecting the public tables. I'm working on the design and I'm wondering if there are any best practices that might help with some particular issues. I want to provide undo capability. I want to show the user the combined result of all their changes. When the user says they're done, I need to check the underlying public data to make sure it hasn't been changed by somebody else. My current plan is to have the user work in a set of tables setup to be a private working area. Once they're ready they can kick off a process to check everything and update the public tables. Undo can be recorded using Command pattern saving to a table. Are there any techniques I might have missed or useful papers or patterns? Thanks in advance!

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• Database relationships using phpmyAdmin (composite keys)

  - by Cool Hand Luke UK

  Hi, I hope this question is not me being dense. I am using phpmyAdmin to create a database. I have the following four tables. Don't worry about that fact place and price are optional they just are. Person (Mandatory) Item (Mandatory) Place (Optional) Price (Optional) Item is the main table. It will always have person linked. * I know you do joins in mysql for the tables. If I want to link the tables together I could use composite keys (using the ids from each table), however is this the most correct way to link the tables? It also means item will have 5 ids including its own. This all cause null values (apparently a big no no, which I can understand) because if place and price are optional and are not used on one entry to the items table I will have a null value there. Please help! Thanks in advance. I hope this makes sense.

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• Establishing persistent connection to a database in Java

  - by gmile

  I've ran through several examples over the web, and found that every single time I need something from the DB, I should write the following code: try { // Step 1: Load the JDBC driver. Class.forName("mysql_driver_name"); // Step 2: Establish the connection to the database. String url = "jdbc:string_to_mysql_server"; Connection conn = DriverManager.getConnection(url,"user1","password"); // fetch from the DB ... } catch (Exception e) { System.err.println("Got an exception! "); System.err.println(e.getMessage()); } It's very annoying to put up this code every time I want something from the DB, so the question is - is there a way to only once connect entirely all my app to the DB somehow at the very start point, avoiding copy-pasting mentioned code, and then be able to do everything I want with DB? I've quickly looked through NetBeans's Project menu, but didn't find any clue on how to configurate a persistent connection to a selected DB. If it's important, i'm writing a purely desktop app, i.e. using Java EE. Also, it's worth mentioning that I'm a kinda beginner in Java.

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• Java login form with database connection

  - by Muhammed Yoosuf

  I am creating a login form in java by having a database connection, and I need 2 open DIFFERENT forms for each user. However, all of the three forms open except for one. The forms I have are, MAinWindow Nursery Primary Secondary ALL THE FORMS OPEN except for the nursery form, when I enter the correct username it displays the Primary form. ANY HELP SOON char[] DBUserArray; DBUserArray=name.toCharArray(); char [] DBPassArray; DBPassArray=pass.toCharArray(); char AdminArray []=AdminUser.toCharArray(); char NurArray []=NurHead.toCharArray(); char[] PriArray =PriHead.toCharArray(); char[] SecArray=SecHead.toCharArray(); char[] input = txtpassword.getPassword(); String user=txtusername.getText(); char [] userString; userString=user.toCharArray(); if(userString.length!=DBUserArray.length && input.length!=DBPassArray.length) { JOptionPane.showMessageDialog(null, "Username and Password Wrong","User Login",JOptionPane.ERROR_MESSAGE); } else { if(userString.length!=AdminArray.length) { if(userString.length!=PriArray.length) { if(userString.length!=NurArray.length) { if(userString.length!=SecArray.length) { } else { new Secondary().setVisible(true); setVisible(false); } } else { new Nursery().setVisible(true); setVisible(false); } } else { new Primary().setVisible(true); setVisible(false); } } else { new MainWindow().setVisible(true); setVisible(false); } }

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• Hierarchical/Nested Database Structure for Comments

  - by Stephen Melrose

  Hi, I'm trying to figure out the best approach for a database schema for comments. The problem I'm having is that the comments system will need to allow nested/hierarchical comments, and I'm not sure how to design this out properly. My requirements are, Comments can be made on comments, so I need to store the tree hierarchy I need to be able to query the comments in the tree hierarchy order, but efficiently, preferably in a fast single query, but I don't know if this is possible I'd need to make some wierd queries, e.g. pull out the latest 5 root comments, and a maximum of 3 children for each one of those I read an article on the MySQL website on this very subject, http://dev.mysql.com/tech-resources/articles/hierarchical-data.html The "Nested Set Model" in theory sounds like it will do what I need, except I'm worried about querying the thing, and also inserting. If this is the right approach, How would I do my 3rd requirement above? If I have 2000 comments, and I add a new sub-comment on the first comment, that will be a LOT of updating to do. This doesn't seem right to me? Or is there a better approach for the type of data I'm wanting to store and query? Thank you

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• Django Database design -- Is this a good stragety for overriding defaults

  - by rh0dium

  Hi SO's I have a question on good database design practices and I would like to leverage you guys for pointers. The project started out simple. Hey we have a bunch of questions we want answered for every project (no problem) Which turned into... Hey we have so many questions can we group them into sections (yup we can do that) Which lead into.. Can we weight these questions and I don't really want some of these questions for my project (Yes but we are getting difficult) And then I'm thinking they will want to have each section have it's own weight.. Requirements So there's the requirements - For n number of project Allow a admin member the ability select the questions for a project Allow the admin member to re-weigh or use the default weights for the questions Allow the admin member to re-weight the sections Allow team members to answer the questions. So here is what I came up with. Please feel free to comment and provide better examples models.py from django.db import models from django.contrib.sites.models import Site from django.conf import settings class Section(models.Model): """ This describes the various sections for a checklist: """ name = models.CharField(max_length=64) description = models.TextField() class Question(models.Model): """ This simply provides a simple way to list out the questions. """ question = models.CharField(max_length=255) answer_type = models.CharField(max_length=16) description = models.TextField() section = models.ForeignKey(Section) class ProjectQuestion(models.Model): """ These are the questions relevant to the project """ question = models.ForeignKey(Question) answer = models.CharField(max_length=255) required = models.BooleanField(default=True) weight = models.FloatField(default = XXX) class Project(models.Model): """ Here is where we want to gather our questions """ questions = models.ManyToManyField(ProjectQuestion) Immediate questions: - When I start a project - any ideas on how to "pre-populate" the questions (and ultimately the weights) for the project? - Is there a generally accepted method for doing this process that I am missing? Basically the idea that you refer to the questions overide your own default weight, and store the answer? - It appears that a good chuck of the work will be done in the views and that a lot of checking will need to occur there? Is that OK? Again - feel free to give me better strategies!! Thanks

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• Simple Database normalization question...

  - by user365531

  Hi all, I have a quick question regarding a database that I am designing and making sure it is normalized... I have a customer table, with a primary key of customerId. It has a StatusCode column that has a code which reflects the customers account status ie. 1 = Open, 2 = Closed, 3 = Suspended etc... Now I would like to have another field in the customer table that flags whether the account is allowed to be suspended or not... certain customers will be automatically suspended if they break there trading terms... others not... so the relevant table fields will be as so: Customers (CustomerId(PK):StatusCode:IsSuspensionAllowed) Now both fields are dependent on the primary key as you can not determine the status or whether suspensions are allowed on a particular customer unless you know the specific customer, except of course when the IsSuspensionAllowed field is set to YES, the the customer should never have a StatusCode of 3 (Suspended). It seems from the above table design it is possible for this to happen unless a check contraint is added to my table. I can't see how another table could be added to the relational design to enforce this though as it's only in the case where IsSuspensionAllowed is set to YES and StatusCode is set to 3 when the two have a dependence on each other. So after my long winded explanation my question is this: Is this a normalization problem and I'm not seeing a relational design that will enforce this... or is it actually just a business rule that should be enforced with a check contraint and the table is in fact still normalized. Cheers, Steve

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• how to get Contact database schema.

  - by kamiomar

  Dear, is there any link that provide me the Contact Schema. when i store new phone number in mobile, the informaion store in the database. so i need schema to create my own table for back purpose. i have alreay get People table column by the follwoing code. boolean displayFlag = false; String str = ""; Uri CONTACT_URI = People.CONTENT_URI; Cursor cursor = mContext.getContentResolver().query(CONTACT_URI, null, null, null, null); String columnNames = ""; if (cursor != null) { try { cursor.getCount(); if (cursor.moveToFirst()) { String[] columns = cursor.getColumnNames(); for (int i = 0; i < columns.length; i++) { columnNames += "colName" + cursor.getColumnName(i) + " : " + cursor.getString(i) + "colValue"; } } } finally { cursor.close(); } } createImage(columnNames); if (displayFlag) { Toast.makeText(mContext, str, Toast.LENGTH_SHORT).show(); } } Thanks

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• How do I query SQLite Database in Android?

  - by kunjaan

  I successfully created the Database and inserted a row however I cannot Query it for some reason. My Droid crashes everytime. String DATABASE_NAME = "myDatabase.db"; String DATABASE_TABLE = "mainTable"; String DATABASE_CREATE = "create table if not exists " + DATABASE_TABLE + " ( value VARCHAR not null);"; SQLiteDatabase myDatabase = null; myDatabase = openOrCreateDatabase(DATABASE_NAME, Context.MODE_PRIVATE, null); myDatabase.execSQL(DATABASE_CREATE); // Create a new row of values to insert. ContentValues newValues = new ContentValues(); // Assign values for each row. newValues.put("value", "kunjan"); // Insert the row into your table myDatabase.insert(DATABASE_TABLE, null, newValues); String[] result_columns = new String[] { "value" }; Cursor allRows = myDatabase.query(true, DATABASE_TABLE, result_columns, null, null, null, null, null, null); if (allRows.moveToFirst()) { String value = allRows.getString(1); TextView foo = (TextView) findViewById(R.id.TextView01); foo.setText(value); } allRows.close(); myDatabase.close();

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