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• Database schema for a library

  - by ABach

  Hi all - I'm designing a library management system for a department at my university and I wanted to enlist your eyes on my proposed schema. This post is primarily concerned with how we store multiple copies of each book; something about what I've designed rubs me the wrong way, and I'm hoping you all can point out better ways to tackle things. For dealing with users checking out books, I've devised three tables: book, customer, and book_copy. The relationships between these tables are as follows: Every book has many book_copies (to avoid duplicating the book's information while storing the fact that we have multiple copies of that book). Every user has many book_copies (the other end of the relationship) The tables themselves are designed like this: ------------------------------------------------ book ------------------------------------------------ + id + title + author + isbn + etc. ------------------------------------------------ ------------------------------------------------ customer ------------------------------------------------ + id + first_name + first_name + email + address + city + state + zip + etc. ------------------------------------------------ ------------------------------------------------ book_copy ------------------------------------------------ + id + book_id (FK to book) + customer_id (FK to customer) + checked_out + due_date + etc. ------------------------------------------------ Something about this seems incorrect (or at least inefficient to me) - the perfectionist in me feels like I'm not normalizing this data correctly. What say ye? Is there a better, more effective way to design this schema? Thanks!

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• c# reading integer fields from database

  - by arnoldino

  what is wrong with this code? try { if (cmd == null) getConnection(); cmd.CommandText = "Select id from HMonthInventary where machine_id=37"; SQLiteDataReader reader = cmd.ExecuteReader(); if (reader.HasRows==true) { reader.Read(); string s = reader[0].ToString(); // return first element reader.Close(); return s; } reader.Close(); return null; } catch (Exception e) { MessageBox.Show("Caught exception: " + e.Message+"|"+cmd.CommandText); return null; } I checked the sql statement, it turns the right value. why can't I read it? the returnvalue is "".

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• design an extendable database model

  - by wishi_

  Hi! Currently I'm doing a project whose specifications are unclear - well who doesn't. I wonder what's the best development strategy to design a DB, that's going to be extended sooner or later with additional tables and relations. I want to include "changeability". My main concern is that I want to apply design patterns (it's a university project) and I want to separate the constant factors from those, that change by choosing appropriate design patterns - in my case MVC and a set of sub-patterns at model level. When it comes to the DB however, I may have to resdesign my model in my MVC approach, because my domain model at a later stage my require a different set of classes representing the DB tables. I use Hibernate as an abstraction layer between DB and application. Would you start with a very minimal DB, just a few tables and relations? And what if I want an efficient DB, too? I wonder what strategies are applied in the real world. Stakeholder analysis for example isn't a sufficient planing solution when it comes to changing requirements. I think - at a DB level - my design pattern ends. So there's breach whose impact I'd like to minimize with a smart strategy.

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• Using a singleton database class in functions and multiple scripts(PHP) - best use methods

  - by dscher

  I have a singleton db connection which I get with: $dbConnect = myDatabase::getInstance(); which is easy enough. My question is what is the least rhetorical and legitimate way of using this connection in functions and classes? It seems silly to have to declare the variable global, pass it into every single function, and/or recreate this variable within every function. Is there another answer for this? Obviously I'm a noob and I can work my way around this problem 10 different ways, none of which is really attractive to me. It would be a lot easier if I could have that $dbConnect variable accessible in any function without needing to declare it global or pass it in. I do know I can add the variable to the $_SERVER array...is there something wrong with doing this? It seems somewhat inappropriate to me. Another quick question: Is it bad practice to do this: $result = myDatabase::getInstance()-query($query); from directly within a function?

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• Database Design for One to One relationships

  - by Greelmo

  I'm trying to finalize my design of the data model for my project, and am having difficulty figuring out which way to go with it. I have a table of users, and an undetermined number of attributes that apply to that user. The attributes are in almost every case optional, so null values are allowed. Each of these attributes are one to one for the user. Should I put them on the same table, and keep adding columns when attributes are added (making the user table quite wide), or should I put each attribute on a separate table with a foreign key to the user table. I have decided against using the EAV model. Thanks!

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• Container for database-like searches

  - by Milan Babuškov

  I'm looking for some STL, boost, or similar container to use the same way indexes are used in databases to search for record using a query like this: select * from table1 where field1 starting with 'X'; or select * from table1 where field1 like 'X%'; I thought about using std::map, but I cannot because I need to search for fields that "start with" some text, and not those that are "equal to". I could create a sorted vector or list and use binary search (breaking the set in 2 in each step by reading the element in the middle and seeing if it's more or less than 'X'), but I wonder if there is some ready-made container I could use without reinventing the wheel?

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• Advantage Database Server: in-memory queries.

  - by ie

  As far as I know, ADS v.10 tries to keep result of query in memory until it is a quite huge. The same should be true for the __output table and for temporary tables. When the result becoming large, swapping stated. The question is what memory limit is set for a query, a worker, whatever? Could this limit be configured? Thanks.

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• Is there a flat-file database that is supported by Silverlight?

  - by Anton Kanevsky

  I am looking for a flat-file (or serverless) database that I can connect to a C# Silverlight application. There has to be one, but I can't find anything. EDIT: SQLite is an example of a flat-file database. A flat-file database in my view is any database that does not require a server. Unfortunately, SQLite does not work with Silverlight. What I want to achieve is to be able to store, update and delete entries from the database. In my application, there is a chart with sectors and nodes. I want to be able to edit sectors and store their settings in the database, and I want to be able to add/retrieve/edit/delete nodes on the chart. The database needs to be free for educational purposes. Thanks.

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• How to Implement Web Based Find File Database Text Search

  - by neversaint

  I have series of files like this: foo1.txt.gz foo2.txt.gz bar1.txt.gz ..etc.. and a tabular format files that describe the file foo1 - Explain foo1 foo2 - Explain foo2 bar1 - Explain bar1 ..etc.. What I want to do is to have a website with a simple search bar and allow people to type foo1 or just foo and finally return the gzipped file(s) and the explanation of the file(s). What's the best way to implement this. Sorry I am totally new in this area.

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• 0.00 decimal fields in MySQL database giving empty value when in a PHP array

  - by SamD

  The fields read as 0.00 in phpMyAdmin, but when put into an array, the value is blank, is there a way to get it to show just '0'? Thanks Sam

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• How to Implement Web Based Find File Database Via Text Search

  - by neversaint

  I have series of files like this: foo1.txt.gz foo2.txt.gz bar1.txt.gz ..etc.. and a tabular format file that describe those files: foo1 - Explain foo1 foo2 - Explain foo2 bar1 - Explain bar1 ..etc.. What I want to do is to have a website with a simple search bar and allow people to type foo1 or just foo and finally return the gzipped file(s) and the related explanation of the file(s). What's the best way to implement this and what kind of tools should I use. Sorry I am totally new in this area.

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• How to insert an n:m-relationship with technical primary keys generated by a sequence?

  - by bitschnau

  Let's say I have two tables with several fields and in every table there is a primary key which is a technical id generated by a database sequence: table1 table2 ------------- ------------- field11 <pk> field21 <pk> field12 field22 field11 and field21 are generated by sequences. Also there is a n:m-relationship between table1 und table2, designed in table3: table3 ------------- field11 <fk> field21 <fk> The ids in table1 und table2 are generated during the insert statement: INSERT INTO table1 VALUES (table1_seq1.NEXTVAL, ... INSERT INTO table2 VALUES (table2_seq1.NEXTVAL, ... Therefore I don't know the primary key of the added row in the data-access-layer of my program, because the generation of the pk happens completely in the database. What's the best practice to update table3 now? How can I gain access to the primary key of the rows I just inserted?

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• Help needed in database design for application of Timetable Generation

  - by Himadri

  I am planning for an application of time-table generation. I wanted the data such as standardname, teachername, standard wise subjects and also relate the corresponding teacher with the subject and standard. I had think like, StandardMaster(stdid,stdname) TeacherMaster(teacherid,teachername) SubjectMaster(subid,subname,stdid) What more I need? Any corrections needed in these three tables?

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• How would I implement separate databases for reading and writing operations?

  - by Matt

  I am interested in implementing an architecture that has two databases one for read operations and the other for writes. I have never implemented something like this and have always built single database, highly normalised systems so I am not quite sure where to begin. I have a few parts to this question. 1. What would be a good resource to find out more about this achitecture? 2. Is it just a question of replicating between two identical schemas, or would your schemas differ depending on the operations, would normalisation vary too? 3. How do you insure that data written to one database is immediately available for reading from the second? Any further help, tips, resources would be appreciated. Thanks.

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• Exporting database on oracle

  - by Adomas

  Hi, I have a DB on oracle on Windows Server 2003. How do I export it with all the data and put it into other Windows server?

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• Database structure for versioning and multiple languages

  - by phobia

  How can I solve the issue of content existing in multiple versions and multiple languages? My current structure: Each content can only have one active version in each language, and that's how I'm curious on how to best solve. Right now I have a column of the contentversions table, which means for each change of active version I have to run a update and set active=false on all version and then a update to set active=true for the piece of content in question.

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• Combining database tables

  - by zSysop

  Hi all, I have two tables which look kind of similar and i was thinking about combining them and thought i would get some input from everyone. Here's what they currently look like: Issues Id | IssueCategory | IssueType | Status | etc.. ------------------------------------------------- 123 | Copier | Broken | Open | 124 | Hardware | Missing | Open | CopierIssueDetails Id | IssueId | SerialNumber | Make | Model | TonerNumber | LastCount --------------------------------------------------------------------- 1 | 123 | W12134 | Dell | X1234 | 12344555 | 500120 HardwareTicketDetails Id | IssueId | EquipmentNumber | Make | Model | Location | Toner | Monitor | Mouse ----------------------------------------------------------------------------------- 1 | 124 | X1123113 | Dell | XXXX | 1st floor | 0 | 1 | 0 What do you guys think about combining these two tables into one. Would it be a good idea or is it better to keep them separated like this? Thanks in advance for any suggestions.

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• Muti-Schema Privileges for a Table Trigger in an Oracle Database

  - by sisslack

  I'm trying to write a table trigger which queries another table that is outside the schema where the trigger will reside. Is this possible? It seems like I have no problem querying tables in my schema but I get: Error: ORA-00942: table or view does not exist when trying trying to query tables outside my schema. EDIT My apologies for not providing as much information as possible the first time around. I was under the impression this question was more simple. I'm trying create a trigger on a table that changes some fields on a newly inserted row based on the existence of some data that may or may not be in a table that is in another schema. The user account that I'm using to create the trigger does have the permissions to run the queries independently. In fact, I've had my trigger print the query I'm trying to run and was able to run it on it's own successfully. I should also note that I'm building the query dynamically by using the EXECUTE IMMEDIATE statement. Here's an example: CREATE OR REPLACE TRIGGER MAIN_SCHEMA.EVENTS BEFORE INSERT ON MAIN_SCHEMA.EVENTS REFERENCING OLD AS OLD NEW AS NEW FOR EACH ROW DECLARE rtn_count NUMBER := 0; table_name VARCHAR2(17) := :NEW.SOME_FIELD; key_field VARCHAR2(20) := :NEW.ANOTHER_FIELD; BEGIN CASE WHEN (key_field = 'condition_a') THEN EXECUTE IMMEDIATE 'select count(*) from OTHER_SCHEMA_A.'||table_name||' where KEY_FIELD='''||key_field||'''' INTO rtn_count; WHEN (key_field = 'condition_b') THEN EXECUTE IMMEDIATE 'select count(*) from OTHER_SCHEMA_B.'||table_name||' where KEY_FIELD='''||key_field||'''' INTO rtn_count; WHEN (key_field = 'condition_c') THEN EXECUTE IMMEDIATE 'select count(*) from OTHER_SCHEMA_C.'||table_name||' where KEY_FIELD='''||key_field||'''' INTO rtn_count; END CASE; IF (rtn_count > 0) THEN -- change some fields that are to be inserted END IF; END; The trigger seams to fail on the EXECUTE IMMEDIATE with the previously mentioned error. EDIT I have done some more research and I can offer more clarification. The user account I'm using to create this trigger is not MAIN_SCHEMA or any one of the OTHER_SCHEMA_Xs. The account I'm using (ME) is given privileges to the involved tables via the schema users themselves. For example (USER_TAB_PRIVS): GRANTOR GRANTEE TABLE_SCHEMA TABLE_NAME PRIVILEGE GRANTABLE HIERARCHY MAIN_SCHEMA ME MAIN_SCHEMA EVENTS DELETE NO NO MAIN_SCHEMA ME MAIN_SCHEMA EVENTS INSERT NO NO MAIN_SCHEMA ME MAIN_SCHEMA EVENTS SELECT NO NO MAIN_SCHEMA ME MAIN_SCHEMA EVENTS UPDATE NO NO OTHER_SCHEMA_X ME OTHER_SCHEMA_X TARGET_TBL SELECT NO NO And I have the following system privileges (USER_SYS_PRIVS): USERNAME PRIVILEGE ADMIN_OPTION ME ALTER ANY TRIGGER NO ME CREATE ANY TRIGGER NO ME UNLIMITED TABLESPACE NO And this is what I found in the Oracle documentation: To create a trigger in another user's schema, or to reference a table in another schema from a trigger in your schema, you must have the CREATE ANY TRIGGER system privilege. With this privilege, the trigger can be created in any schema and can be associated with any user's table. In addition, the user creating the trigger must also have EXECUTE privilege on the referenced procedures, functions, or packages. Here: Oracle Doc So it looks to me like this should work, but I'm not sure about the "EXECUTE privilege" it's referring to in the doc.

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• Database Patterns

  - by Onorio Catenacci

  Does anyone know of papers/books/etc. that document patterns for databases? For example, one common rule of thumb is that every table should have a primary key and that the key should be devoid of information content. So I was wondering if anyone had written a book or published papers regarding design patterns for designing relational databases?

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• Database Error django

  - by Megan

  DatabaseError at /admin/delmarva/event/ no such column: delmarva_event.eventdate I created a class in my models.py file: from django.db import models from django.contrib.auth.models import User class Event(models.Model): eventname = models.CharField(max_length = 100) eventdate = models.DateField() eventtime = models.TimeField() address = models.CharField(max_length = 200) user = models.ForeignKey(User) def __unicode__(self): return self.eventname and now when i try to view my events in my admin or my main_page it gives me the error that there is no eventdate. I tried syncing the db again but nothing changed. Also, I hashtagged eventdate out to see if I get a different error and then it states that delmarva_event.eventtime does not exist as well. I It is weird because it does not have a problem with eventname. Any suggestions would be greatly appreciated!

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• General question: Filesystem or database?

  - by poeschlorn

  Hey guys, i want to create a small document management system. there are several users who store their files. each file which is uploaded contains an info which user uploaded it and the document content itself. In a view there are displayed all files of ONE specific user, ordered by date. What would be better: 1) giving the documents a name or metadata(XML) which contain the date and user (and iterate through them to get the metadata) or 2) giving the files a random/unique name and store metadata in a DB? something like this: date | user | filename What would you say and why? The used programming language is java and the DB is MySQL.

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• Compressing a database to a single file?

  - by Assimilater

  Hi all. In my contact manager program I have been storing information by reading and writing comma delimited files for each individual contact, and storing notes in a file for each note, and I'm wondering how I could go about shrinking them all into one file effectively. I have attempted using data entry tools in the visual studio toolbox and template class, though I have never quite figured out how to use them. What would be especially convenient is if I could store data as data type IOwner (a class I created) as opposed to strings. I'd also need to figure out how to tell the program what to do when a file is opened (I've noticed in the properties how to associate a file type with the program though am not sure how to tell it what to do when it's opened). Edit: How about rephrasing the question: I have a class IContact with various properties some of them being lists of other class objects. I have a public list of IContact. Can I write Contacts as List(Of IContact) to a file as opposed to a bunch of strings? Second part of the question: I have associated .cms files with my program. But if a user opens the file, what code should the program run through in an attempt to deal with the file? This file is going to contain data that the program needs to read, how do I tell it to read a file when the program is opened vicariously because the file was opened? Does this make the question clearer?

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• designing database tables using JDBC

  - by Noona

  I am creating a users table using JDBC and mysql, each user has a permissions list that comprises Integer values, I am wondering if I should use an array for storing these values and then have only 1 record for this user in the table, or simply create a new table that comprises 2 columns: user ID and permissions, and then have multiple records for each user that specify the user name in one columns and one permission value in the second column, the second option seems to be redundant since a permission value is a simple object that isn't associated with any other objects (like a student and courses list for example, because the course is associated with many other objects, like grade, teacher, etc, so in this case it is natural to have multiple records), but the first one seems to be a bit unnatural to me, so if someone has experience with these things and direct me? thanks

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• Mysql Master Slave Replication on Large Database table (how to sync initial data)

  - by Brian Lovett

  We have a production server and a dev server. We have found that backups are nearly impossible on the production server because of the query volume we experience. So, we're looking at setting up replication with our dev server being the slave. This is ideal because we can afford to lock the tables on that server and additionally it will be nice to have up to date data for the developers. Now, the issues. The production server can't really be taken down or locked at this point, at least not easily. We have a high query volume and fairly large 30+ GB innodb tables. Both servers are running all innodb and are also both on mysql 5.1. What can we do to sync the data initially to get replication started? I've tried a few options, but so far, none have worked.

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• Voting Script, Possibility of Simplifying Database Queries

  - by Sev

  I have a voting script which stores the post_id and the user_id in a table, to determine whether a particular user has already voted on a post and disallow them in the future. To do that, I am doing the following 3 queries. SELECT user_id, post_id from votes_table where postid=? AND user_id=? If that returns no rows, then: UPDATE post_table set votecount = votecount-1 where post_id = ? Then SELECT votecount from post where post_id=? To display the new votecount on the web page Any better way to do this? 3 queries are seriously slowing down the user's voting experience Edit In the votes table, vote_id is a primary key In the post table, post_id is a primary key. Any other suggestions to speed things up?

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