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  • SQLAlchemy - relationship limited on more than just the foreign key

    - by Marian
    I have a wiki db layout with Page and Revisions. Each Revision has a page_id referencing the Page, a page relationship to the referenced page; each Page has a all_revisions relationship to all its revisions. So far so common. But I want to implement different epochs for the pages: If a page was deleted and is recreated, the new revisions have a new epoch. To help find the correct revisions, each page has a current_epoch field. Now I want to provide a revisions relation on the page that only contains its revisions, but only those where the epochs match. This is what I've tried: revisions = relationship('Revision', primaryjoin = and_( 'Page.id == Revision.page_id', 'Page.current_epoch == Revision.epoch', ), foreign_keys=['Page.id', 'Page.current_epoch'] ) Full code (you may run that as it is) However this always raises ArgumentError: Could not determine relationship direction for primaryjoin condition ...`, I've tried all I had come to mind, it didn't work. What am I doing wrong? Is this a bad approach for doing this, how could it be done other than with a relationship?

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  • Alternative design for a synonyms table?

    - by Majid
    I am working on an app which is to suggest alternative words/phrases for input text. I have doubts about what might be a good design for the synonyms table. Design considerations: number of synonyms is variable, i.e. football has one synonym (soccer), but in particular has two (particularly, specifically) if football is a synonym to soccer, the relation exists in the opposite direction as well. our goal is to query a word and find its synonyms we want to keep the table small and make adding new words easy What comes to my mind is a two column design with col a = word and col b = delimited list of synonyms Is there any better alternative? What about using two tables, one for words and the other for relations?

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  • Design for tagging system in GAE-J

    - by tempy
    I need a simple tagging system in GAE-J. As I see it, the entity that is being tagged should have a collection of keys referring to the tags with which it's associated. A tag entity should simply contain the tag string itself, and a collection of keys pointing to the entities associated with the tag. When an entity's list of tags is altered, the system will create a new tag if the tag is unknown, and then append the entity's key to that tag's key collection. If the tag already exists, then the entity's key is simply appended to the tag's key collection. This seems relatively straight-forward and uncontroversial to me, but I would like some feedback on this design, just to be sure.

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  • DB design for master file in enterprise software

    - by Thang Nguyen
    Dear all. I want to write an enterprise software and now I'm in the DB design phase. The software will have some master data such as Suppliers, Customers, Inventories, Bankers... I considering 2 options: Put each of these on one separate table. The advantage: the table will have all necessary information for that kind of master file (Customer: name, address,.../Inventory: Type, Manufacturer, Condition...). Disadvantage: Not flexible. When I want to have a new type of master data, such as Insurer, I have to design another table. Put all in one table and this table have foreign key to another table which have type of each kind of master data (table 1: id, data_type, code, name, address....; table 2: data_type, data_type_name). Advantage: flexible - if I want more master data such as Insurer, I just put in table 2: code: 002, name: Insurer, and then put detail each insurer into table 1). Disadvantage: table 1 must have sufficient field to store all kind of information including: customer name, address, account, inventory's manufacturer, inventory's quality...). So which method do you usually do (or you think work better). Thank you very much

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  • How to track history of db tables that include many-to-many mapping tables?

    - by chacmool
    I have seen several questions here on tracking db history, but can't seem to find one that matches our situation. We need to track the history of several tables, some of which are many-to-many linking tables. Eg say we have this schema: EntityA id name EntityB id name ABLink A_id B_id So, tracking changes to EntityA or EntityB seems pretty straightforward. We can keep a log table with the same columns plus a date stamp and user. But what about the links? How do we maintain the set of links that are valid for a given version of the data? We need to be able to recreate a history of the data showing changes in chronological order. So if a link added or deleted, we indicate that. Etc.

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  • How do I modify an attribute across all rows in a table?

    - by prgmatic
    Hi folks, My apologies for asking such a novice question but, I need help building a script using either PHP or directly in MySQL that can do the following: Take the values of a column in a table (text) Change them into capitalized words (from "this is a title" to "This Is A Title") Replace the old values (uncapitalized) with the new values (capitalized). Thanks for the help and support.

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  • Multiple rows update trigger

    - by sony
    If I have a statement that updates multiple rows, only the trigger will fire only on the first or last row that is being updated (not sure which one). I need to make a trigger that fires for ALL the records that are being updated into a particular table

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  • What's the best way to migrate a Django DB from SQLite to MySQL?

    - by Inshim
    I need to migrate my db from sqlite to mysql, and the various tools/scripts out there are too many for me to easily spot the safest and most elegant solution. This seemed to me nice http://djangosnippets.org/snippets/14/ but appears to be 3 years since getting an update which is worrying.. Can you recommend a solution that is known to be reliable with Django 1.1.1 ?

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  • Preg_match differences?

    - by sky
    Hi, i want to ask, what is the meaning or difference between these two line? if( preg_match_all('/\#([?-?À-ÿ?-??-?a-z0-9\-_]{1,50})/iu', $message, $matches, PREG_PATTERN_ORDER) ) { if( preg_match_all('/\#([?-?a-z0-9\-_\x{4e00}-\x{9fa5}]{1,50})/iu', $message, $matches, PREG_PATTERN_ORDER) ) { and what does the number 3 mean in this line? (Arrow pointing) if( preg_match_all('/\@([a-zA-Z0-9\-_\x{4e00}-\x{9fa5}]{->3,30})/u', $message, $matches, PREG_PATTERN_ORDER) ) { Thanks!

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  • What is the scope of TRANSACTION in Sql server

    - by Shantanu Gupta
    I was creating a stored procedure and i got stuck in the writing methodology of me and my collegue. I am using SQL Server 2005 I was writing Stored procedure like this BEGIN TRAN BEGIN TRY INSERT INTO Tags.tblTopic (Topic, TopicCode, Description) VALUES(@Topic, @TopicCode, @Description) INSERT INTO Tags.tblSubjectTopic (SubjectId, TopicId) VALUES(@SubjectId, @@IDENTITY) COMMIT TRAN END TRY BEGIN CATCH DECLARE @Error VARCHAR(1000) SET @Error= 'ERROR NO : '+ERROR_NUMBER() + ', LINE NO : '+ ERROR_LINE() + ', ERROR MESSAGE : '+ERROR_MESSAGE() PRINT @Error ROLLBACK TRAN END CATCH And my collegue was writing it like the below one BEGIN TRY BEGIN TRAN INSERT INTO Tags.tblTopic (Topic, TopicCode, Description) VALUES(@Topic, @TopicCode, @Description) INSERT INTO Tags.tblSubjectTopic (SubjectId, TopicId) VALUES(@SubjectId, @@IDENTITY) COMMIT TRAN END TRY BEGIN CATCH DECLARE @Error VARCHAR(1000) SET @Error= 'ERROR NO : '+ERROR_NUMBER() + ', LINE NO : '+ ERROR_LINE() + ', ERROR MESSAGE : '+ERROR_MESSAGE() PRINT @Error ROLLBACK TRAN END CATCH Here the only difference that you will find is the position of writing Begin TRAN. According to me the methodology of my collegue should not work when an exception occurs i.e. Rollback should not get executed because TRAN does'nt have scope. But when i tried to run both the code, both was working in the same way. I am confused to know how does TRANSACTION works. Is it scope free or what ?

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  • Hierarchical Data in MySQL is fast to retrieve?

    - by ajsie
    i've got a list of all countries - states - cities (- subcities/villages etc) in a XML file and to retrieve for example a state's all cities it's really quick with XML (using xml parser). i wonder, if i put all this information in mysql, is retrieving a state's all cities as fast as with XML? cause XML is designed to store hierarchical data while relational databases like mysql are not. the list contains like 500 000 entities. so i wonder if its as fast as XML using either of: Adjacency list model Nested Set model And which one should i use? Cause (theoretically) there could be unlimited levels under a state. And which is fastest for this huge dataset? Thanks!

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  • Hierarchical Data in MySQL is as fast as XML to retrieve?

    - by ajsie
    i've got a list of all countries - states - cities (- subcities/villages etc) in a XML file and to retrieve for example a state's all cities it's really quick with XML (using xml parser). i wonder, if i put all this information in mysql, is retrieving a state's all cities as fast as with XML? cause XML is designed to store hierarchical data while relational databases like mysql are not. the list contains like 500 000 entities. so i wonder if its as fast as XML using either of: Adjacency list model Nested Set model And which one should i use? Cause (theoretically) there could be unlimited levels under a state (i heard that adjacency isn't good for unlimited child-levels). And which is fastest for this huge dataset? Thanks!

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  • Need help with SQL Query

    - by StackOverflowNewbie
    Say I have 2 tables: Person - Id - Name PersonAttribute - Id - PersonId - Name - Value Further, let's say that each person had 2 attributes (say, gender and age). A sample record would be like this: Person->Id = 1 Person->Name = 'John Doe' PersonAttribute->Id = 1 PersonAttribute->PersonId = 1 PersonAttribute->Name = 'Gender' PersonAttribute->Value = 'Male' PersonAttribute->Id = 2 PersonAttribute->PersonId = 1 PersonAttribute->Name = 'Age' PersonAttribute->Value = '30' Question: how do I query this such that I get a result like this: 'John Doe', 'Male', '30'

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  • sql 2008 express connection problems

    - by user163457
    Hi, I've just installed a fresh copy of SQL 2008 Express. before I did anything I opened Management Studio and successfully connected using Window Authentication. However I tried to run the following on the command line "telnet localhost 1433" and got the error "Could not open connection to the host, on port 1433: Connect failed" I checked netstat and there is nothing listening on port 1433. Before I go any further, is there a problem with the install? thanks, Shane

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  • Using a remote PHP service with Flex (Flash Builder) AIR Application?

    - by Chrisc
    Hello, I'm developing a Adobe AIR application using Flash Builder 4. This app needs to access a remote PHP service which is being hosted on a remote web server. I am having troubles figuring out how to add a PHP data service which uses a remote service. I can add the PHP data service in Flash Builder as a service hosted on localhost, but given that this will not be feasible when the application is deployed, will not work. Does anyone know how to connect a Flash Builder (Flex) project to a remote PHP data service? Thanks, Chris

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  • Is it possible to partition more than one way at a time in SQL Server?

    - by meeting_overload
    I'm considering various ways to partition my data in SQL Server. One approach I'm looking at is to partition a particular huge table into 8 partitions, then within each of these partitions to partition on a different partition column. Is this even possible in SQL Server, or am I limited to definining one parition column+function+scheme per table? I'm interested in the more general answer, but this strategy is one I'm considering for Distributed Partitioned View, where I'd partition the data under the first scheme using DPV to distribute the huge amount of data over 8 machines, and then on each machine partition that portion of the full table on another parition key in order to be able to drop (for example) sub-paritions as required.

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  • mysql GROUP_CONCAT

    - by user301766
    I want to list all users with their corropsonding user class. Here are simplified versions of my tables CREATE TABLE users ( user_id INT NOT NULL AUTO_INCREMENT, user_class VARCHAR(100), PRIMARY KEY (user_id) ); INSERT INTO users VALUES (1, '1'), (2, '2'), (3, '1,2'); CREATE TABLE classes ( class_id INT NOT NULL AUTO_INCREMENT, class_name VARCHAR(100), PRIMARY KEY (class_id) ); INSERT INTO classes VALUES (1, 'Class 1'), (2, 'Class 2'); And this is the query statement I am trying to use but is only returning the first matching user class and not a concatenated list as hoped. SELECT user_id, GROUP_CONCAT(DISTINCT class_name SEPARATOR ",") AS class_name FROM users, classes WHERE user_class IN (class_id) GROUP BY user_id; Actual Output +---------+------------+ | user_id | class_name | +---------+------------+ | 1 | Class 1 | | 2 | Class 2 | | 3 | Class 1 | +---------+------------+ Wanted Output +---------+---------------------+ | user_id | class_name | +---------+---------------------+ | 1 | Class 1 | | 2 | Class 2 | | 3 | Class 1, Class 2 | +---------+---------------------+ Thanks in advance

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  • Non-Access or -base QBE tool?

    - by idbin.cath0br0
    Hello. I'm currently looking for a QBE tool that can execute queries on PostgreSQL or MySQL. OS doesn't really matter. Reason is that we've got to do QBE at school but I don't want to use neither Microsoft Access nor OpenOffice.org Base (lack of features). Any help would be appreciated.

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  • Any disadvantages to this tagging approach

    - by donpal
    I have a table of tags ID tag --- ------ 1 tagt 2 tagb 3 tagz 4 tagn In my items table, I'm using those tags in serialized format, comma delimited ID field1 tags ---- ------ ----- 1 value1 tagt,tagb 2 value2 tagb 3 value3 tagb,tagn 4 value4 When I need to find items that have this tag, I plan to deserialize the tags. But I'm not actually sure how to do it, and if it's better to have a third table for associations instead between the tags and the items.

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  • cached data base

    - by radi
    hi , in my project i need a tow tables each of it has about 2000 row , i want my application to be speed so my db should load into memory (cached) when the app start and before it close the db have to be saved on the disk . i am using java and i want to use sql

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