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• Join ACM, join IEEE, or read programming books?

  - by Laura

  I read blogs and listen to podcasts, and I own many of the "classic" programming books. For the money, what kind of printed material would you say is the most valuable to keep current in software engineering -- books, or magazines from professional organizations such as ACM and IEEE? Which organization has the best periodicals?

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• Database structure - To join or not to join

  - by Industrial

  Hi! We're drawing up the database structure with the help of mySQL Workbench for a new app and the number of joins required to make a listing of the data is increasing drastically as the many-to-many relationships increases. The application will be quite read-heavy and have a couple of hundred thousand rows per table. The questions: Is it really that bad to merge tables where needed and thereby reducing joins? Should we start looking at horizontal partitioning? (in conjunction with merging tables) Is there a better way then pivot tables to take care of many-to-many relationships? We discussed about instead storing all data in serialized text columns and having the application make the sorting instead of the database, but this seems like a very bad idea, even though that the database will be heavily cached. What do you think? Thanks!

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• nHibernate Self Join Mapping

  - by kmoo01

  Hi Guys, This is probably incredibly simple, but I just cant see the wood for the trees at the moment. For brevity, I would like to model a word object, that has related words to it (synonyms), In doing so I could have the following mappings: <class name="Word" table="bs_word"> <id name="Id" column="WordId" type="Int32" unsaved-value="-1"> <generator class="native"> <param name="sequence"></param> </generator> </id> <property name="Key" column="word" type="String" length="50" /> <many-to-one name="SynonymGroup" class="BS.Core.Domain.Synonym, BS.Core" column="SynonymId" lazy="false"/> <class name="Synonym" table="bs_Synonym"> <id name="Id" column="SynonymId" type="Int32" unsaved-value="-1"> <generator class="native"> <param name="sequence"></param> </generator> </id> <property name="Alias" column="Alias" type="String" length="50" /> <bag name="Words" cascade="none" lazy="false" inverse="true"> <key column="SynonymId" /> <one-to-many class="Word" /> </bag> Mapping it like this would mean for a given word, I can access related words (synonyms) like this: word.SynonymGroup.Words However I would like to know if it is possible to map a bag of objects on an instance of a word object...if that makes sense, so I can access the related words like this: word.Words I've tried playing around with the map element, and composite elements, all to no avail - so I was wondering if some kind person could point me in the right direction? ta, kmoo01

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• boost thread, test if thread is ready to join

  - by aaa

  hi. I would like to know if there is a way to test whenever thread finished execution and is waiting for joining. My guess was the use time_join. is there explicit way to test it?

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• Mysql JOIN problem

  - by FinalDestiny

  I have 2 mysql tables : Question with the following columns : id, question, nranswers Nranswers must be a number from 1 to 5 And the other table is Answers with the following columns: userid, answer . Now the problem is that I want to get the replies for each answer for one question(id 22 let's say) . P.S. If the nranswers is 3, the result should look like this: (the right number means how many times the reply number was chosen) 1 - 2 2 - 8 3 - 7 If the nranswers is 5, the result should look like this: 1 - 3 2 - 8 3 - 14 4 - 19 5 - 8 Please help me out with the query, atm he's not counting the answers that weren't chosen, only the ones that were chosen at least one time.

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• SQL join: where clause vs. on clause

  - by BCS

  After reading it, this is not a duplicate of Explicit vs Implicit SQL Joins. The answer may be related (or even the same) but the question is different. What is the difference and what should go in each? If I understand the theory correctly, the query optimizer should be able to use both interchangeably.

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• Help with MySQL Join Statement

  - by JasonS

  Hi, I just built a website and have realised that I need to have a top 3 highest rated albums.. I haven't built in something that keeps track of the ratings. Ratings are stored separately. Can someone show me how to put these together please. SELECT id, name FROM albums LIMIT 3 SELECT rating FROM ratings WHERE url=CONCAT('albums/show/', album.id) Let me just flesh it out a bit. I need to get back the following: From the albums table. id, name. From the ratings table I need to get back the average rating. ROUND((rating+rating+rating) / total ratings) The ratings. Users can rate everything on my website so I have a generic ratings table. The rating is stored with the url of the page it applies to. Hence, to get album ratings I need to have 'albums/show/{album_id}'. In hind sight I should have had a type and id field but it is a bit late now with a lunch iminient. Any help is much appreciated.

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• Join one row to multiple rows in another table

  - by Ghostrider

  I have a table to entities (lets call them people) and properties (one person can have an arbitrary number of properties). Ex: People Name Age -------- Jane 27 Joe 36 Jim 16 Properties Name Property ----------------- Jane Smart Jane Funny Jane Good-looking Joe Smart Joe Workaholic Jim Funny Jim Young I would like to write an efficient select that would select people based on age and return all or some of their properties. Ex: People older than 26 Name Properties Jane Smart, Funny, Good-looking Joe Smart, Workaholic It's also acceptable to return one of the properties and total property count. The query should be efficient: there are millions of rows in people table, hundreds of thousands of rows in properties table (so most people have no properties). There are hundreds of rows selected at a time. Is there any way to do it?

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• SQL Join Statement

  - by mouthpiec

  Hi I have the following SQL SELECT statement SELECT bar_id, bar_name, town_name, advert_text FROM bar, towns, baradverts WHERE town_id = town_id_fk AND bar_id = bar_id_fk My problem is that since not every bar has an advert in table "baradverts", these bars are not coming up in the results. In other words I need a NULL for those bars that do not have an advert string.

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• Using attr_accessible in a join model with has_many :through relationship

  - by Paulo Oliveira

  I have a USER that creates a COMPANY and become an EMPLOYEE in the process. The employees table has an :user_id and a :company_id. class User has_many :employees has_many :companies, :through => :employees class Employee belongs_to :user belongs_to :company attr_accessible :active class Company has_many :employees has_many :users, :through => employees Pretty basic. But here's the thing, the resource EMPLOYEE has other attributes than its foreign keys, like the boolean :active. I would like to use attr_accessible, but this causes some problems. The attribute :user_id is set right, but :company_id is nil. @user.companies << Company.new(...) Employee id:1 user_id:1 company_id:nil So my question is: if :user_id is set right, despite it is not an attr_accessible, why :company_id isn't set right just the same? It shouldn't be an attr_accessible. I'm using Rails 3.0.8, and have also tested with 3.0.7.

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• To join or not to join - database structure

  - by Industrial

  Hi! We're drawing up the database structure with the help of mySQL Workbench for a new app and the number of joins required to make a listing of the data is increasing drastically as the many-to-many relationships increases. The questions: Is it really that bad to merge tables where needed and thereby reducing joins? Is there a better way then pivot tables to take care of many-to-many relationships? We discussed about instead storing all data in serialized text columns and having the application make the sorting instead of the database, but this seems like a very bad idea, even though that the database will be heavily cached. What do you think? Thanks!

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• MySQL join problem

  - by David

  Table1 has u_name, Table2 has u_name, u_type and u_admin Table1.u_name is unique. But neither of the 3 fields in Table2 is unique. For any value of Table1.u_name, there are 0 to many entries in Table2 that Table2.u_name equals to that value. For any value of Table1.u_name, there are 0 to 1 entries in Table2 that Table2.u_name equals to that value AND Table2.u_type='S' What I want: Use Table1.u_name to get Table1.*, Table2.u_admin where Table1.u_name=Tabl2.u_name and Table2.u_type='S'. If there is no such entry in Table2 we still need to get Table1.* Please help give me some hints. Thank you so much!

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• MySQL Select Statement - Two Tables, Sort One Table by Count of Other Table

  - by Robert Boka

  So I have built a voting system for a custom post system i wrote. I want to be able to sort by "most voted", "Most liked", etc. I have two tables. Entry: ID, Title, Post Vote: ID, EntryID, Result I want to be able to query the vote table for each entry and see how many vote's there are, and then sort the entry's by how many vote's each table had. I have messed around with joins, etc. and cannot seem to figure it out. Any suggestions?

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• Oracle join query

  - by Jasim

  There are three tables in my db ITEM_MASTER, PRICE_MASTER, COMP_MASTER ITEM_MASTER STORE_CODE ITEM_CODE ITEM_DESC 011 914004 desccc PRICE_MASTER STORE_CODE ITEM_CODE COMP_CODE 011 914004 01 011 914004 02 011 914004 03 011 914004 04 COMP_MASTER COMP_CODE COMP_DESC STORE_CODE 01 comp1 011 02 comp2 011 03 comp3 011 04 comp4 011 I want to get all these for an ITEM_CODE in single query STORE_CODE ITEM_CODE ITEM_DESC COMP_DESC1 COMP_DESC2 COMP_DESC3 COMP_DESC4 011 914004 desccc comp1 comp2 comp3 comp4 How can i write a oracle SQL query for this??

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• sfDoctrineGuard - how to ALWAYS join sfGuardProfile to sfGuardUser

  - by prodigitalson

  I want to make it so that anytime the db is queried for an sfGuardUserProfile it is autmoatically joined and hydrated with its related sfGuardUser. If i was using propel i would normally override the doSelectStmt method of the sfGuardUserProfilePeer class to inspect the Criteria and modify it as necessary as well as modifying the hydrate method of the sfGuardUserProfile class. Im not sure how to go about doing this in Doctrine though.

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• Ruby on Rails updating join table records

  - by Eef

  Hey, I have two models Users and Roles. I have setup a many to many relationship between the two models and I have a joint table called roles_users. I have a form on a page with a list of roles which the user checks a checkbox and it posts to the controller which then updates the roles_users table. At the moment in my update method I am doing this because I am not sure of a better way: role_ids = params[:role_ids] user.roles.clear role_ids.each do |role| user.roles << Role.find(role) end unless role_ids.nil? So I am clearing all the entries out then looping threw all the role ids sent from the form via post, I also noticed that if all the checkboxes are checked and the form posted it keeps adding duplicate records, could anyone give some advice on a more efficent way of doing this?

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• How to add condition on multiple-join table

  - by Jean-Philippe

  Hi, I have those two tables: client: id (int) #PK name (varchar) client_category: id (int) #PK client_id (int) category (int) Let's say I have those datas: client: {(1, "JP"), (2, "Simon")} client_category: {(1, 1, 1), (2, 1, 2), (3, 1, 3), (4,2,2)} tl;dr client #1 has category 1, 2, 3 and client #2 has only category 2 I am trying to build a query that would allow me to search multiple categories. For example, I would like to search every clients that has at least category 1 and 2 (would return client #1). How can I achieve that? Thanks!

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• MySQL: 4 Table "has-many-through" Join?

  - by Nebs

  Let's say I have the following 4 tables (for examples' sake): Owners, Trucks, Boxes, Apples. An owner can have many trucks, a truck can have many boxes and a box can have many apples. Owners have an id. Trucks have an id and owner_id. Boxes have an id and truck_id. Apples have an id and box_id. Let's say I want to get all the apples "owned" by an owner with id = 34. So I want to get all the boxes that are in boxes that are in trucks that owner 34 owns. There is a "hierarchy" if you will of 4 tables that each only has reference to its direct "parent". How can I quickly filter boxes while satisfying conditions across the other 3 tables? I hope that made sense somewhat. Thanks.

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• LINQ Left Join And Right Join

  - by raja

  Hi, I need a help, I have two dataTable called A and B , i need all rows from A and matching row of B Ex: A: B: User | age| Data ID | age|Growth 1 |2 |43.5 1 |2 |46.5 2 |3 |44.5 1 |5 |49.5 3 |4 |45.6 1 |6 |48.5 I need Out Put: User | age| Data |Growth ------------------------ 1 |2 |43.5 |46.5 2 |3 |44.5 | 3 |4 |45.6 |

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• problem with join SQL Server 2000

  - by eyalb

  I have 3 tables - Items, Props, Items_To_Props i need to return all items that match all properties that i send example items 1 2 3 4 props T1 T2 T3 items_to_props 1 T1 1 T2 1 T3 2 T1 3 T1 when i send T1,T2 i need to get only item 1

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• Need help building SQL Query (simple JOIN)

  - by Newbie

  Hello! In my database, I have a "users", a "quests" and a "questings" table. A user can solve a quest. Solving a quest will save the "user_id" and the "quest_id" in my "questings" table. Now, I want to select all quests, a user has NOT solved (meaning there is no entry for this user and quest in "questings" table)! Let's say the user has the id 14. How to write this query? After solving this query, I want to filter the results, too. A quest and a user has a city, too. What to do for writing a query which returns all quests, a user has NOT solved yet, in the users city (user city == quest city)?

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• Grails - Need to restrict fetched rows based on condition on join table

  - by sector7

  Hi guys, I have these two domains Car and Driver which have many-to-many relationship. This association is defined in table tblCarsDrivers which has, not surprisingly, primary keys of both the tables BUT additionally also has a new boolean field deleted. Herein lies the problem. When I find/get query on domain Car, I am fetched all related drivers irrespective of their deleted status in tblCarsDrivers, which is expected. I need to put a clause/constraint to exclude the deleted drivers from the list of fetched records. PS: I tried using an association domain CarDriver in joinTable name but that seems not to work. Apparently it expects only table names, not maps. PPS: I know its unnatural to have any other fields besides the mapping keys in mapping table but this is how I got it and it cant be changed. Car domain is defined as such - class Car { Integer id String name static hasMany = [drivers:Driver] static mapping = { table 'tblCars' version false drivers joinTable:[name: 'tblCarsDrivers',column:'driverid',key:'carid'] } } Thanks!

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• mysql join on two indexes takes long time!!

  - by Alaa

  Hi All I have a custom query in dripal, this query is: select count(distinct B.src) from node A, url_alias B where concat('node/',A.nid)= B.src; now, nid in node is primary key and i have made src as an index in url_alias table. after waiting for more than a minute i got this: +-----------------------+ | count(distinct B.src) | +-----------------------+ | 325715 | +-----------------------+ 1 row in set (1 min 24.37 sec) now my question is: why did this query take this long, and how to optimize it?? Thanks for your help

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• Fetch last item in a category that fits specific criteria

  - by Franz

  Let's assume I have a database with two tables: categories and articles. Every article belongs to a category. Now, let's assume I want to fetch the latest article of each category that fits a specific criteria (read: the article does). If it weren't for that extra criteria, I could just add a column called last_article_id or something similar to the categories table - even though that wouldn't be properly normalized. How can I do this though? I assume there's something using GROUP BY and HAVING?

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• Finding group maxes in SQL join result

  - by Gene

  Two SQL tables. One contestant has many entries: Contestants Entries Id Name Id Contestant_Id Score -- ---- -- ------------- ----- 1 Fred 1 3 100 2 Mary 2 3 22 3 Irving 3 1 888 4 Grizelda 4 4 123 5 1 19 6 3 50 Low score wins. Need to retrieve current best scores of all contestants ordered by score: Best Entries Report Name Entry_Id Score ---- -------- ----- Fred 5 19 Irving 2 22 Grizelda 4 123 I can certainly get this done with many queries. My question is whether there's a way to get the result with one, efficient SQL query. I can almost see how to do it with GROUP BY, but not quite. In case it's relevant, the environment is Rails ActiveRecord and PostgreSQL.

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