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• Composite Primary and Cardinality

  - by srini.venigalla

  I have some questions on Composite Primary Keys and the cardinality of the columns. I searched the web, but did not find any definitive answer, so I am trying again. The questions are: Context: Large (50M - 500M rows) OLAP Prep tables, not NOSQL, not Columnar. MySQL and DB2 1) Does the order of keys in a PK matter? 2) If the cardinality of the columns varies heavily, which should be used first. For example, if I have CLIENT/CAMPAIGN/PROGRAM where CLIENT is highly cardinal, CAMPAIGN is moderate, PROGRAM is almost like a bitmap index, what order is the best? 3) What order is the best for Join, if there is a Where clause and when there is no Where Clause (for views) Thanks in advance.

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• Multiple Table Joins to Improve Performance?

  - by EdenMachine

  If I have a table structure like this: Transaction [TransID, ...] Document [DocID, TransID, ...] Signer [SignerID, ...] Signature [SigID, DocID, SignerID, ...] And the business logic is like this: Transactions can have multiple documents Documents can have multiple signatures And the same signer can have multiple signatures in multiple documents within the same transaction So, now to my actual question: If I wanted to find all the documents in a particular transaction, would it be better, performance-wise, if I also stored the TransID and the DocID in the Signer table as well so I have smaller joins. Otherwise, I'd have to join through the Signature Document Transaction Documents to get all the documents in the transaction for that signer. I think it's really messy to have that many relationships in the Signer table though and it doesn't seem "correct" to do it that way (also seems like an update nightmare) but I can see that it might be better performance for direct joins. Thoughts? TIA!

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• SQL help - find the table that has 'somefieldId' as the primary key?

  - by Kettenbach

  Hello All, How can I search my sql database for a table that contains a field 'tiEntityId'. This field is referenced in a stored procedure, but I am unable to identify which table this id is a primary key for? Any suggestions? I currently look through stored procedure definitions for references to text by using something like this Declare @Search varchar(255) SET @Search='[10.10.100.50]' SELECT DISTINCT o.name AS Object_Name,o.type_desc FROM sys.sql_modules m INNER JOIN sys.objects o ON m.object_id=o.object_id WHERE m.definition Like '%'+@Search+'%' ORDER BY 2,1 Any SQL guru's out there know what I need to use to find the table that contains the field, 'preferably the table where that field is the Primary Key. Thanks so much for any tips. Cheers, ~ck in San Diego

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• Including associations optimization in Rails

  - by Vitaly

  Hey, I'm looking for help with Ruby optimization regarding loading of associations on demand. This is simplified example. I have 3 models: Post, Comment, User. References are: Post has many comments and Comment has reference to User (:author). Now when I go to the post page, I expect to see post body + all comments (and their respective authors names). This requires following 2 queries: select * from Post -- to get post data (1 row) select * from Comment inner join User -- to get comment + usernames (N rows) In the code I have: Post.find(params[:id], :include => { :comments => [:author] } But it doesn't work as expected: as I see in the back end, there're still N+1 hits (some of them are cached though). How can I optimize that?

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• Get a DB result with a value between two columns values

  - by vitto

  Hi, I have a database situation where I'd like to get a user profile row by a user age range. this is my db: table_users username age email url pippo 15 [email protected] http://example.com pluto 33 [email protected] http://example.com mikey 78 [email protected] http://example.com table_profiles p_name start_age_range stop_age_range young 10 29 adult 30 69 old 70 inf I use MySQL and PHP but I don't know if there is some specific tacnique to do this and of course if it's possible. # so something like: SELECT * FROM table_profiles AS profiles INNER JOIN table_users AS users # can I do something like this? ON users.age IS BETWEEN profiles.start_age_range AND profiles.stop_age_range

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• VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum relation

  - by vukis

  Hi. I have following situation: I need to join VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum and take VendTable.Vendgroup. In all cases (queries,or even views) Dynamics ax joins tables VendInvoiceJour.OrderAccount<- VendTable.AccountNum not VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum. I`m trying to use this kind of query: qBdSVendJour = element.query().dataSourceTable(tablenum(VendInvoiceJour)); qBdSVendTbl = qBdSVendJour.addDataSource(tablenum(VendTable)); qBdSVendTbl.relations(true); qBdSVendTbl.joinMode(JoinMOde::InnerJoin); qBdSVendTbl.fetchMode(QueryFetchMode::One2One); qBdSVendTbl.addLink(FieldNum(VendInvoiceJour,InvoiceAccount),FieldNum(VendTable,AccountNum));//(Dynamics ax automaticaly corrects InvoiceAccount to orderaccount in reports if trying this link in morphx)

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• Howto check if a object is connected to another in hibernate

  - by codevourer

  Imagine two domain object classes, A and B. A has a bidirectional one-to-many relationship to B. A is related to thousands of B. The relations must be unique, it's not possible to have a duplicate. To check if an instance of B is already connected to a given instance of A, we could perform an easy INNER JOIN but this will only ensure the already persisted relations. What about the current transient relations? class A { @OneToMany private List<B> listOfB; } If we access the listOfB and perform a check of contains() this will fetch all the connected instances of B lazy from the datasource. I only want to validate them by their primary-key. Is there an easy solution where I can do things like "Does this instance of A is connected with this instance of B?" Without loading all these data into memory and perform a based on collections?

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• Eager loading in EF1.0

  - by Dave Swersky

  I have a many-to-many relationship: Application - Applications_Servers - Server This is set up in my Entity Data Model and all is well. My problem is that I'd like to eager-load the whole graph of Applications so that I have an IEnumerable<Applications>, each Application member populated with the Servers collection associated by the many-to-many relationship. Normally this wouldn't be a problem, but according to my research there must be a navigation property between Application and Server. This is not the case for me because my Applications_Servers join table has more in it than just the two keys. Therefore, there is no navigation property directly between Application and Server, and this doesn't work: var apps = (from a in context.Application.Include("Server") select a).ToList(); I get an error saying there is no navigation property on Application called "Server", and that's correct, there is none. How do I write the query to eager-load my Applications with their Servers in this case?

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• Error 500 on template.render() with jinja2

  - by Asperitas

  I am working on playing with some Python to create a webapp. At first I put the HTML in a string, using %s to fill certain elements. That all worked perfectly. Now I want to put the HTML in a template, so I followed this tutorial. My code looks like this (I deleted irrelevant code for this error): import codecs import cgi import os import jinja2 jinja_environment = jinja2.Environment(loader=jinja2.FileSystemLoader(os.path.join(os.path.dirname(__file__)))) class Rot13Handler(webapp2.RequestHandler): def get(self): template = jinja_environment.get_template('rot13.html') self.response.out.write(template.render({'text': ''})) When I replace just template.render({'text': ''}) a random string, the program works fine. I did add the latest jinja2 library to my app.yaml, and naturally my rot13.html does exist with the {{ text }} added. So could anyone please help me in the right direction? I don't know why it's going wrong.

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• How to handle large table in MySQL ?

  - by Frantz Miccoli

  I've a database used to store items and properties about these items. The number of properties is extensible, thus there is a join table to store each property associated to an item value. CREATE TABLE `item_property` ( `property_id` int(11) NOT NULL, `item_id` int(11) NOT NULL, `value` double NOT NULL, PRIMARY KEY (`property_id`,`item_id`), KEY `item_id` (`item_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; This database has two goals : storing (which has first priority and has to be very quick, I would like to perform many inserts (hundreds) in few seconds), retrieving data (selects using item_id and property_id) (this is a second priority, it can be slower but not too much because this would ruin my usage of the DB). Currently this table hosts 1.6 billions entries and a simple count can take up to 2 minutes... Inserting isn't fast enough to be usable. I'm using Zend_Db to access my data and would really be happy if you don't suggest me to develop any php side part. Thanks for your advices !

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• Add all lines multiplied by another line in another table

  - by russell

  Hi, I hope I can explain this good enough. I have 3 tables. wo_parts, workorders and part2vendor. I am trying to get the cost price of all parts sold in a month. I have this script. $scoreCostQuery = "SELECT SUM(part2vendor.cost*wo_parts.qty) as total_score FROM part2vendor INNER JOIN wo_parts ON (wo_parts.pn=part2vendor.pn) WHERE workorder=$workorder"; What I am trying to do is each part is in wo_parts (under partnumber [pn]). The cost of that item is in part2vendor (under part number[pn]). I need each part price in part2vendor to be multiplied by the quantity sold in wo_parts. The way all 3 tie up is workorders.ident=wo_parts.workorder and part2vendor.pn=wo_parts.pn. I hope someone can assist. The above script does not give me the same total as when added by calculator.

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• Converting delimited string to multiple values in mysql

  - by epo

  I have a mysql legacy table which contains an client identifier and a list of items, the latter as a comma-delimited string. E.g. "xyz001", "foo,bar,baz". This is legacy stuff and the user insists on being able to edit a comma delimited string. They now have a requirement for a report table with the above broken into separate rows, e.g. "xyz001", "foo" "xyz001", "bar" "xyz001", "baz" Breaking the string into substrings is easily doable and I have written a procedure to do this by creating a separate table, but that requires triggers to deal with deletes, updates and inserts. This query is required rarely (say once a month) but has to be absolutely up to date when it is run, so e.g. the overhead of triggers is not warranted and scheduled tasks to create the table might not be timely enough. Is there any way to write a function to return a table or a set so that I can join the identifier with the individual items on demand?

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• Best way to construct this query?

  - by Andrew

  I have two tables set up similar to this (simplified for the quest): actions- id - user_id - action - time users - id - name I want to output the latest action for each user. I have no idea how to go about it. I'm not great with SQL, but from what I've looked up, it should look something like the following. not sure though. SELECT `users`.`name`, * FROM users, actions JOIN < not sure what to put here > ORDER BY `actions`.`time` DESC < only one per user_id > Any help would be appreciated.

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• Automatic open Colorbox modal window

  - by user1631168

  I'm using the Colorbox module in Drupal 7. I'm opening an external website. I can make it work with a link. Click here, then click the "colorbox popup" link at the bottom, middle column. The client would like this to open automatically when the page opens. I've created a block and added the following code (from the colorbox site). <script type="text/javascript"> // Display a welcome message on first visit, and set a cookie that expires in 30 days: if (document.cookie.indexOf('visited=true') === -1) { var expires = new Date(); expires.setDate(expires.getDate()+30); document.cookie = "visited=true; expires="+expires.toUTCString(); jQuery.colorbox({html:"http://join.raretearepublic.com/popup/", width:887, height:638}); } </script> But it does not work. Any help would be greatly appreciated.

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• mongoDB many to many with one query?

  - by PowderKeg

  in mysql i use JOIN and one query is no problem. what about mongo? imagine categories and products. products may have more categories. categories may have more product. (many to many structure) and administrator may edit categories in administration (categories must be separated) its possible write product with categories names in one query? i used this structure categories { name:"categoryName", product_id:["4b5783300334000000000aa9","5783300334000000000aa943","6c6793300334001000000006"] } products { name:"productName", category_id:["4b5783300334000000000bb9","5783300334000000000bb943","6c6793300334001000000116"] } now i can simply get all product categories, and product in some category and categories alone for editation. but if i want write product with categories names i need two queries - one to get product categories id and second to get categories names from categories by that ids. is this the right way? or this structure is unsuitable? i would like to have only one query but i dont know if its possible.

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• Ordering by multiple columns in mysql with subquery

  - by Scarface

  Hey guys I have a query that selects data and organizes but not in the correct order. What I want to do is select all the comments for a user in that week and sort it by each topic, then sort the cluster by the latest timestamp of each comment in their respective cluster. My current query selects the right data, but in seemingly random order. Does anyone have any ideas? select * from ( SELECT topic.topic_title, topic.topic_id FROM comments JOIN topic ON topic.topic_id=comments.topic_id WHERE comments.user='$user' AND comments.timestamp>$week order by comments.timestamp desc) derived_table group by topic_id

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• Designing a peer to peer network

  - by Varun

  I am designing a simple peer to peer network. The basic architecture will be as follows: A central server- that keeps track of all the peers. The job of this server is to keep track of all the peers that join the network. Every peer could do things: a. Download a file from it's peer b. Push a file (send a file) to it's peer. Could anybody please tell me what would be the best design for such a system? What would be the problems that i might run into and so on. I am planning to use Java as the programming language to implement. Would it be a good choice? Also, is it necessary that i would need a Linux box to develop the system? or is it fine if i use a Windows machine? Your help will be much appreciated! Thanks!

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• How to split movie and play parts to look as a whole?

  - by luksow

  I'm writing software which is demonstraiting video on demand service. One of the feature is something similiar to IIS Smooth Streaming - I want to adjust quality to the bandwith of the client. My idea is, to split single movie into many, let's say - 2 seconds parts, in different qualities and then send it to the client and play them. The point is that for example first part can be in very high quality, and second in really poor (if the bandwith seems to be poor). The question is - do you know any software that allows me to cut movies precisly? For example ffmpeg splits movies in a way that join is visible and really annoying (seconds are the measure of precision). I use qt + phonon as a player if it matters. Or maybe you know any better way to provide such feature, without splitting movie into parts?

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• Help needed in AdventureWorks in a sql query.

  - by vaibhav

  I was just playing with adventureworks database in sqlserver. I got stuck in a query. I wanted to Select all titles from HumanResources.Employee which are either 'Male' or 'Female' but not both. i.e if title Accountant is Male and Female both I want to leave that title. I need only those titles where Gender is either Male or Female. I have done this till yet. select distinct(title) from humanresources.employee where gender='M' select distinct(title) from humanresources.employee where gender='F' Probably a join between these two queries, would work. But If you have any other solution, please let me know. It is not a homework. :) Thanks in advance.

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• Do I need to include all fields in my entity framework model

  - by Jim B

  Quick question for everyone: Do I need to include all the database table fields on my EF model? For example; I've created a sub-model that only deals with tblPayment and associated tables. Now, I need to write a LINQ query to get some information about items. I would typically get this by joining tblPayment to tblInvoice to tblInvoiceItem to finally tblOrderItem. I'm wondering if when I add in those other tables, do I need to include all the fields for tblInvoice and tblInvoiceItem? Ideally; I'd just like to keep the fields I'd need to join on, as that would limit the possibility of my sub-model breaking if other fields on those tables are modified/deleted. Can I do this?

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• Partioning the Table into .net - Creating columner database.

  - by Omky

  Hello Geeks, I am developing some tool for BI. There are terms like Fact, Dimensions and Measures. My application will connect to the normal database and read the data from that table. Now, I want to convert all this data into columnar database. That is all the columns from this table will be transfer into 3 tables each. Consider below table:- ID Product 1 XYZ 2 ABC 3 ABC Now, I want to convert the Product column i.e. dimension into 3 tables. dim_product_table:- ID Product 1 XYZ 2 ABC dim_product_fmk(fact map by key):- Where we will store key-value pair of Key Row 1 1 1 2 2 3 dim_product_fmr(fact map by row):- The above table will be reversed. Row Key 1 1 2 1 3 2 The another requirement is all above table should be generated dynamically and I should be able to JOIN all those. Can anybody help me? Thanks in advance.

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• How do I do multiple has_and_belongs_to_many associations between the same two classes?

  - by Ermin

  I have the following setup: class Publication < ActiveRecord::Base has_and_belongs_to_many :authors, :class_name=>'Person', :join_table => 'authors_publications' has_and_belongs_to_many :editors, :class_name=>'Person', :join_table => 'editors_publications' end class Person < ActiveRecord::Base has_and_belongs_to_many :publications end With this setup I can do stuff like Publication.first.authors. But if I want to list all publications in which a person is involved Person.first.publications, an error about a missing join table people_publications it thrown. How could I fix that? Should I maybe switch to separate models for authors and editors? It would however introduce some redundancy to the database, since a person can be an author of one publication and an editor of another.

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• What are good resources for computer graphics basics?

  - by Hanno Fietz

  During Flex programming, I recently ran into several questions (about box models, ways to join lines and misaligning pixels [on doctype]) regarding computer graphics and layout, where I felt that I lacked some basic background on things like concepts like the box model approaches mapping real numbers to a pixel raster (like font anti-aliasing) conventions found across drawing engines, like do you count y coordinates from top or bottom, and why I feel that reading some basic Wikipedia articles, books or tutorials on these subjects might help in phrasing my questions more specifically and debugging my code more systematically. I have repeatedly found myself writing tiny test apps in Flex, just to find out how the APIs do very basic stuff. My assumption would be that if I knew the right vocabulary and some general concepts, I could solve these questions much faster.

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• How to display how many times each records in a table used by other table

  - by Fredy

  I have a problem with my query, below are two tables that tbl_tag and tbl_tag_usedby. I want to show how much of each record in tbl_tag used by record in tbl_tag_usedby. Here is a query that I use: SELECT t.*, COUNT(u.tagid) AS totale FROM tbl_tag t LEFT JOIN tbl_tag_usedby u ON u.tagid = t.id AND t.status =1 GROUP BY u.tagid and the results are as below: In this case the record id from 2 to 6 do not appear in the query results, I want record id from 2 to 6 are also shown and on the field "totale" its value is 0. Can anyone help me?

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• Browser based online game question

  - by Emre

  I am developing a small browser based game in asp.net. Think of a game room which has a capaticy of 22 players and players join the room by clicking a button. ( I am saving the number of players in the room in database) I need to call a method when the number of players in the room is 22. The problem is I don't know how to control the number of players in the room. I mean I think like there need to be a bacground code which has to run all the time at the server and that code controls the number and call the function. It's my first web project(school project) and I hope you all can help me.

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