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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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  • 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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  • 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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  • 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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  • Help with MySQL database structure - user notification system

    - by Simon
    Hi, I'd like to send global notifications to my users (1000+ users) and allow them to close the notification box once they have read the message. Basically I may send one notification per week globally ie/ each user get the same message and they are not personal in nature. What is the best way to achieve this? Create 2 tables: **tb_messages** message_id massage_title message_content **tb_read_messages** user_id message_id is-read That way i can just show each user the current notifications that are not read? select * from tb_read_messages WHERE user_id = $user_id AND is-read = no OR is there a more efficient way? Thanks!!!

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  • How to use SOCI C++ Database library?

    - by NeDark
    I'm trying to implement soci in my program but I don't know how. I'm using C++ on linux, on a project on netbeans. I have followed the steps in http://soci.sourceforge.net/doc/structure.html to install it, and I tried to copy the files soci.h from /src/core and soci-mysql.h from /src/backends/mysql in my proyect but it gives compilation error (these files include other soci files, but it's illogical to copy all files into the directory...). I have read the guide several time but I don't understand what I'm doing wrong, the examples only include these files. Thanks. Edit: I have given more information in a comment below the answer. I don't know what steps I have to do to implement soci.

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  • database assignment

    - by eric
    Hi, Given the following table: CREATE TABLE T1 (A INTEGER NOT NULL); CREATE TABLE T3 (A SMALLINT NOT NULL); INSERT T1 VALUES (32768.5); SELECT * FROM T1; INSERT T3 SELECT * FROM T1; SELECT * FROM T3; What is the output of above query? If any error occured please declare the line of it?Explain your answer!

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  • database table design

    - by e.b.white
    I design the tables as below for the system which looks like a package delivering system For example, after user received the package, postman should record in system, and the state(history table) is "delivered",and operator is this postman, the current state(state table) is of course "delivered" history table: +---------------+--------------------------+ | Field | Desc | +---------------+--------------------------+ | id | PRIMARY KEY | +---------------+--------------------------+ | package_id | package_tacking_id | +---------------+--------------------------+ | state | package_state | +---------------+--------------------------+ | operators | operators | +---------------+--------------------------+ | create_time| create_time | +---------------+--------------------------+ state table: +---------------+--------------------------+ | Field | Desc | +---------------+--------------------------+ | id | PRIMARY KEY | +---------------+--------------------------+ | package_id | package_tacking_id | +---------------+--------------------------+ | state | latest_package_state | +---------------+--------------------------+ Above is just the basic information to record, some other information( like invoice, destination,...) should be recored as well. But there are different service types like s1 and s2, for s1 it is not needed to record invoice but s1 need, and maybe s1 need some other information to record (like the tel of end user). After all, at delivering way stations there are additional information to record, and for different service type the information type is different. My question is: 1. For different service type, shall I need to declare different tables(option A) or just one big table which can record all information for all types(option B)? 2. If option A, since the basic information above is MUST, how can prevent from declaring there duplicate fields in different tables?

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  • database transaction rollback processing in PHP

    - by user198729
    try { $con->beginTransaction(); $this->doSave($con); $con->commit(); } catch (Exception $e) { $con->rollBack(); throw $e; } The code above is quite standard an approach to deal with transactions, but my question is:what if $con->rollBack() also fails? It may cause db lock,right?If so,what's the perfect way to go?

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  • How to organise a many to many relationship in MongoDB

    - by Gareth Elms
    I have two tables/collections; Users and Groups. A user can be a member of any number of groups and a user can also be an owner of any number of groups. In a relational database I'd probably have a third table called UserGroups with a UserID column, a GroupID column and an IsOwner column. I'm using MongoDB and I'm sure there is a different approach for this kind of relationship in a document database. Should I embed the list of groups and groups-as-owner inside the Users table as two arrays of ObjectIDs? Should I also store the list of members and owners in the Groups table as two arrays, effectively mirroring the relationship causing a duplication of relationship information? Or is a bridging UserGroups table a legitimate concept in document databases for many to many relationships? Thanks

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  • Generating text file from database

    - by Goldmember
    I have a requirement to hand-code an text file from data residing in a SQL table. Just wondering if there are any best practices here. Should I write it as an XMLDocument first and transform using XSL or just use Streamwriter and skip transformation altogether? The generated text file will be in EDIFACT format, so layout is very specific.

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  • Database design -- does it respect 3rd NF?

    - by Flavius
    Hi I have the following relations (tables) in a relational model Person person_id, first_name, last_name, address Student person_id, matr_nr Teacher person_id, salary Lecture lecture_id, lect_name, lect_description Attendees lecture_id, person_id, date I'm wondering about the functional dependencies of Student and Teacher. Do these tables respect the 3rd normal form? Which should be the primary keys of these tables?

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  • Database model for storing expressions and their occurrence in text

    - by lisak
    Hey, I'm doing a statistical research application. I need to store words according to 2 initial letters which is 676 combinations and each word has its number of occurrences (minimal, maximal, average) in text. I'm not sure how the model/schema should look like. There will be a lot of checking whether the keyword was already persisted. I appreciate your suggestions. Edit: I'll be using either mysql or postgresql + spring templates

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  • Unstructured database design

    - by Linh
    Hi all, According to normal way, we design the table with fields. Example with an article the table can contain fields as follows: title, content, author..... But how does everybody think if we add up some fields to a field?

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  • Do I need a spatial index in my database?

    - by Sanoj
    I am designing an application that needs to save geometric shapes in a database. I haven't choosen the database management system yet. In my application, all database queries will have an bounding box as input, and as output I want all shapes within that database. I know that databases with a spatial index is used for this kind of application. But in my application there will not be any queries of type "give me objects nearby x/y" or other more complex queries that are useful in a GIS application. I am planning of having a database without a spatial index and have queries looking like: SELECT * FROM shapes WHERE x < max_x AND x > min_x AND y < max_y AND y > min_y And have an index on the columns x (double) and y (double). As long I can see, I don't really need a database with an spatial index, howsoever my application is close to that kind of applications. And even if I would like to have nearby queries, then I could create a big enough bounding box around that point. Or will this lead to poor performance? Do I really need a spatial database? And when is a spatial index needed?

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  • Generic Database table design

    - by Gazeth
    Just trying to figure out the best way to design my table for the following scenario: I have several areas in my system (documents, projects, groups and clients) and each of these can have comments logged against them. My question is should I have one table like this: CommentID DocumentID ProjectID GroupID ClientID etc Where only one of the ids will have data and the rest will be NULL or should I have a seperate CommentType table and have my comments table like this: CommentID CommentTypeID ResourceID (this being the id of the project/doc/client) etc My thoughts are that option 2 would be more efficient from an indexing point of view?

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  • Lookups in Multi-Tenant Database

    - by Huthaifa Afanah
    I am developing a SaaS application and I am looking for the best way to design lookup tables, taking in consideration: The look-up tables will have predefined data shared among all the tenants Each tenant must have the ability to extend the look-up table with his own data e.g adding a car class not defined I am thinking about adding TenantID column to each lookup and add the predefined data with setting that column to some value which represents the "Super Tenant" that belongs to the system itself

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  • Customers and suppliers database design issue

    - by hectorsq
    I am developing a web application in which I will have customers and suppliers. Initially I thought on using a Customers table and a Suppliers table. Then when I was thinking on bank transactions, I noticed that each transaction needs to refer to a customer or a supplier, so I thought on using a single table named Business in which I will save both customers and suppliers. If I use Customers and Suppliers tables when I want to list the bank transactions I will have to search in both tables to get the company name. If I use a Businesses table I will have to use a business type column, and have the union of possible fields for all businesses types. Any suggestions on the design?

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  • Comma separated values in a database field

    - by John Doe
    I have a products table. Each row in that table corresponds to a single product and it's identified by a unique Id. Now each product can have multiple "codes" associated with that product. For example: Id | Code ---------------------- 0001 | IN,ON,ME,OH 0002 | ON,VI,AC,ZO 0003 | QA,PS,OO,ME What I'm trying to do is create a stored procedure so that I can pass in a codes like "ON,ME" and have it return every product that contains the "ON" or "ME" code. Since the codes are comma separated, I don't know how I can split those and search them. Is this possible using only TSQL? Edit: It's a mission critical table. I don't have the authority to change it.

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  • Using Multiple Databases

    - by sergiuoala
    A company is hired by another company for helping in a certain field. So I created the following tables: Companies: id, company name, company address Administrators: (in relation with companies) id, company_id, username, email, password, fullname Then, each company has some workers in it, I store data about workers. Hence, workers has a profession, Agreement Type signed and some other common things. Now, the parent tables and data in it for workers (Agreement Types, Professions, Other Common Things) are going to be the same for each company. Should I create 1 new database for each company? Or store All data into the same database? Thanks.

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  • Simple question on database query.

    - by GK
    I have been asked in an interview, To write a sql query which fetches the first three records with highest value on some column from a table. i had written a query which fetched all the records with highest value, but didnt get how exactly i can get only first three records of those. could you help me in this. thanks.

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