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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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• More Tables or More Databases?

  - by BuckWoody

  I got an e-mail from someone that has an interesting situation. He has 15,000 customers, and he asks if he should have a database for their data per customer. Without a LOT more data it’s impossible to say, of course, but there are some general concepts to keep in mind. Whenever you’re segmenting data, it’s all about boundary choices. You have not only boundaries around how big the data will get, but things like how many objects (tables, stored procedures and so on) that will be involved, if there are any cross-sections of data (do they share location or product information) and – very important – what are the security requirements? From the answer to these types of questions, you now have the choice of making multiple tables in a single database, or using multiple databases. A database carries some overhead – it needs a certain amount of memory for locking and so on. But it has a very clean boundary – everything from objects to security can be kept apart. Having multiple users in the same database is possible as well, using things like a Schema. But keeping 15,000 schemas can be challenging as well. My recommendation in complex situations like this is similar to a post on decisions that I did earlier – I lay out the choices on a spreadsheet in rows, and then my requirements at the top in the columns. I  give each choice a number based on how well it meets each requirement. At the end, the highest number wins. And many times it’s a mix – perhaps this person could segment customers into larger regions or districts or products, in a database. Within that database might be multiple schemas for the customers. Of course, he needs to query across all customers, that becomes another requirement. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Using SQL tables for storing user created level stats. Is there a better way?

  - by Ivan

  I am developing a racing game in which players can create their own tracks and upload them to a server. Players will be able to compare their best track times to their friends and see world records. I was going to generate a table for each track submitted to store the best times of each player who plays the track. However, I can't predict how many will be uploaded and I imagine too many tables might cause problems, or is this a valid method? I considered saving each player's best times in a string in a single table field like so: level1:00.45;level2:00.43;level3:00.12 If I did this I wouldn't need a separate table for each level (each level could just have a row in a 'WorldRecords' table). However, this just causes another problem because the text would eventually reach the limit for varchar length. I also considered storing the times data in XML files. This would avoid database issues and server disk space can be increased if needed. But I imagine this would be very slow. To update one players best time on one level, I would have to check every node in the file to find their time record to update. Apologies for the wall of text. Any suggestions would be appreciated.

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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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• More Tables or More Databases?

  - by BuckWoody

  I got an e-mail from someone that has an interesting situation. He has 15,000 customers, and he asks if he should have a database for their data per customer. Without a LOT more data it’s impossible to say, of course, but there are some general concepts to keep in mind. Whenever you’re segmenting data, it’s all about boundary choices. You have not only boundaries around how big the data will get, but things like how many objects (tables, stored procedures and so on) that will be involved, if there are any cross-sections of data (do they share location or product information) and – very important – what are the security requirements? From the answer to these types of questions, you now have the choice of making multiple tables in a single database, or using multiple databases. A database carries some overhead – it needs a certain amount of memory for locking and so on. But it has a very clean boundary – everything from objects to security can be kept apart. Having multiple users in the same database is possible as well, using things like a Schema. But keeping 15,000 schemas can be challenging as well. My recommendation in complex situations like this is similar to a post on decisions that I did earlier – I lay out the choices on a spreadsheet in rows, and then my requirements at the top in the columns. I  give each choice a number based on how well it meets each requirement. At the end, the highest number wins. And many times it’s a mix – perhaps this person could segment customers into larger regions or districts or products, in a database. Within that database might be multiple schemas for the customers. Of course, he needs to query across all customers, that becomes another requirement. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• SQL Server database with clustered GUID PKs - switch clustered index or switch to sequential (comb)

  - by Eyvind

  We have a database in which all the PKs are GUIDs, and most of the PKs are also the clustered index for the table. We know that this is bad (due to the random nature of GUIDs). So, it seems there are basically two options here (short of throwing out GUIDs as PKs altogether, which we cannot do (at least not at this time)). We could change the GUID generation algorithm to e.g. the one that NHibernate uses, as detailed in this post, or we could, for the tables that are under the heaviest use, change to a different clustered index, e.g. an IDENTITY column, and keep the "random" GUIDs as PKs. Is it possible to give any general recommendations in such a scenario? The application in question has 500+ tables, the largest one presently at about 1,5 million rows, a few tables around 500 000 rows, and the rest significantly lower (most of them well below 10K). Furthermore, the application is installed at several customer sites already, so we have to take any possible negative effects for existing customer into consideration. Thanks!

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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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• MS SQL Database with clustered GUID PKs - switch clustered index or switch to sequential (comb) GUID

  - by Eyvind

  We have a database in which all the PKs are GUIDs, and most of the PKs are also the clustered index for the table. We know that this is bad (due to the random nature of GUIDs). So, it seems there are basically two options here (short of throwing out GUIDs as PKs altogether, which we cannot do (at least not at this time)). We could change the GUID generation algorithm to e.g. the one that NHibernate uses, as detailed in this post, or we could, for the tables that are under the heaviest use, change to a different clustered index, e.g. an IDENTITY column, and keep the "random" GUIDs as PKs. Is it possible to give any general recommendations in such a scenario? The application in question has 500+ tables, the largest one presently at about 1,5 million rows, a few tables around 500 000 rows, and the rest significantly lower (most of them well below 10K). Furthermore, the application is installed at several customer sites already, so we have to take any possible negative effects for existing customer into consideration. Thanks!

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• Adapt beginner C# SQL Server INSERT example to work with my database

  - by Mike Bertelsen

  I have read TONS of tutorials, articles and whatever regarding my issue and honestly, due to my lack of experience I can't twist my fingers around this one so I hope some of you guys can help me out :) I am working on a project (simply to learn how to program so it's probably very basic), but I have this "News" page where I can update and delete data using a GridView. Now I would like to INSERT something into my database using 3 textboxes and 1 submit button. I have 3 rows that has to be inserted: Headline Date Content/the news itself. Which are stored under NyhedTB from the connectionstring: BoligStjernenConnectionString My query looks like this: INSERT INTO [NyhedTB] ([NyhedDato], [NyhedTitel], [NyhedTekst]) VALUES (@NyhedDato, @NyhedTitel, @NyhedTekst) I read on the internet that this code should do the magic for me (I will have to insert my own values ofc.): static void Insert() { try { string connectionString = "server=.;" + "initial catalog=employee;" + "user id=sa;" + "password=sa123"; using (SqlConnection conn = new SqlConnection(connectionString)) { conn.Open(); using (SqlCommand cmd = new SqlCommand("INSERT INTO EmployeeDetails VALUES(" + "@Id, @Name, @Address)", conn)) { cmd.Parameters.AddWithValue("@Id", 1); cmd.Parameters.AddWithValue("@Name", "Amal Hashim"); cmd.Parameters.AddWithValue("@Address", "Bangalore"); int rows = cmd.ExecuteNonQuery(); //rows number of record got inserted } } } catch (SqlException ex) { //Log exception //Display Error message } } I looked at this code and thought it should be easy enough but really, I can't figure it out.

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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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• 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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• 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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• Displaying Many-To-Many Database relationship in VB.NET 2008 with DataGrid, MS SQL 2008

  - by user337501

  Computer bombed while posting this, couldnt find a duplicate question but if there is one, forgive me. So, I've run into a wall. And rather than use a ladder to avoid it, I'd like go through it. I'm setting up what I can best describe as a many-to-many relationship in a database. To examplify, imagine I have three primary tables: Items, Categories, Sections(nevermind the potential redundancy) Then I have another table, Properties. Items, Categories, and Sections can be associated with many properties. A single property can be associated with one, all, or none of the other tables. The best way I can figure to do this is to have join tables make the relationship. i.e. tblItems----(Foreign Key)----tblItems_To_Properties----(Foreign Key)----tblProperties In this example, tblItems simply has an "ItemID" Primary Key. tblItems_To_Properties has its own Primary Key(tblItems_To_PropertiesID), a Foreign Key to the Item(ItemID) and a Foreign key to the Property(PropertyID). The Properties table simply has its primary key(PropertyID) I hope this example isnt too confusing...if I have to I can find a way to put a diagram up or something. My problem is, I want to display this in a DataGrid using the Master-Detail method(DevExpress GridControl). I use the tblItems as a test, and I can see the Items in the parent view, but in the child view I see(understandably) the join table and that is it. My goal is to make it so the Grid ignores the join table and shows the Properties table as the only child. Any help on this method or insight into another solution would be muuuuuuuch appreciat

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• choosing row (from group) with max value in a SQL Server Database

  - by sriehl

  I have a large database and am putting together a report of the data. I have aggregated and summed the data from many tables to get two tables that look like the following. id | code | value id | code | value 13 | AA | 0.5 13 | AC | 2.0 13 | AB | 1.0 14 | AB | 1.5 14 | AA | 2.0 13 | AA | 0.5 15 | AB | 0.5 15 | AB | 3.0 15 | AD | 1.5 15 | AA | 1.0 I need to get a list of id's, with the code (sumed from both tables) with the largest value. 13 | AC 14 | AA 15 | AB There are 4-6 thousand records and it is not possible to change the original tables. I'm not too worried about performance as I only need to run it a few times a year. edit: Let me see if I can explain a bit more clearly, imagine the id is the customer id, the code is who they ordered from and the value is how much they spent there. I need a list of the all the customer id's and the store that customer spent the most money at (and if they spent the same at two different stores, put a value such as 'ZZ' in for the store name).

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• SQL database problems with addressbook table design

  - by Sebastian Hoitz

  Hello! I am writing a addressbook module for my software right now. I have the database set up so far that it supports a very flexible address-book configuration. I can create n-entries for every type I want. Type means here data like 'email', 'address', 'telephone' etc. I have a table named 'contact_profiles'. This only has two columns: id Primary key date_created DATETIME And then there is a table called contact_attributes. This one is a little more complex: id PK #profile (Foreign key to contact_profiles.id) type VARCHAR describing the type of the entry (name, email, phone, fax, website, ...) I should probably change this to a SET later. value Text (containing the value for the attribute). I can now link to these profiles, for example from my user's table. But from here I run into problems. At the moment I would have to create a JOIN for each value that I want to retrieve. Is there a possibility to somehow create a View, that gives me a result with the type's as columns? So right now I would get something like #profile type value 1 email [email protected] 1 name Sebastian Hoitz 1 website domain.tld But it would be nice to get a result like this: #profile email name website 1 [email protected] Sebastian Hoitz domain.tld The reason I do not want to create the table layout like this initially is, that there might always be things to add and I want to be able to have multiple attributes of the same type. So do you know if there is any possibility to convert this dynamically? If you need a better description please let me know. Thank you!

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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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• 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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• 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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• 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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• 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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• Properly populating tables in an Object Relational database

  - by chaosTechnician

  I've got a homework assignment that requires that I use Oracle 10g Express to implement an Object Relational database to track phone billing data. I have a superclass of Communications with subclasses of Call, Text, and Data. I'm hitting a snag with properly populating these tables so that I can find the appropriate data in the various tables. My Types and Tables are declared as such: create type CommunicationType as object ( -- column names here ) not final; create type CallType under CommunicationType ( -- column names here ); create type TextType under CommunicationType ( -- column names here ); create type DataType under CommunicationType ( -- column names here ); create table Communications of CommunicationType ( -- Primary and Foreign key constraints here ); create table Calls of CallType; create table Texts of TextType; create table Datas of DataType; When I try to insert data into one of the subclasses, its entry doesn't appear in the superclass. Likewise if I insert into the superclass, it doesn't show up in the appropriate subclass. For example, insert into Calls values (CallType( -- Values -- )); doesn't show any data in Communications. Nor does insert into Communications values (CallType( -- Values -- )); show anything in Calls. What am I doing wrong?

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