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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Query scope within a table trigger in an Oracle database

    - by sisslack
    I'm been trying to write a table trigger the 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. The documentation seems to elude to this notion, but it's not 100% clear to me.

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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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