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• Rails advanced queries with join and sum calculation

  - by Dustin Brewer

  I have two models: companies and expenses. Companies have many expenses and expenses belong to companies. My expense model has an 'amount' column. I was wondering if there is a way to perform a find based on a date range and the amount column of the expenses. Something like top 3 companies by total expense amounts over a 7 day period. I've tried for the better part of the day to get this to work, I've attempted joins, chaining named scopes, raw sql, etc. and I'm not having any luck. Thanks for the help.

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• Hibernate Criteria: Return different entity type than rooted entity?

  - by Gilean

  I have entities similar to: ProductLine: id, name ProductLineContents: content_id, product_line_id Content: id, text, updated_time What I'd like to do is: for each product line, get the latest content (so if theres two content entries associated to one product line, the latest updated_time is rturned, and if one content item is associated to two product lines, it is returned twice). Something similar to: select content.* from productline inner join productlinecontents inner join content; However I can't seem to figure out how to have Hibernate Criteria return a different entity than the original one it was created with. So if I wanted to start the criteria at the product line with createCriteria(ProductLine.class) along with the proper joins, then it only returns ProductLine objects, but I need Content objects. What's the best way to accomplish this? The actual data model is much more complex and can't be modified

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• How to search in this activerecord example?

  - by Horace Ho

  Two models: Invoice :invoice_num string :date datetime . . :disclaimer_num integer (foreign key) Disclaimer :disclaimer_num integer :version integer :body text For each disclaimer there are multiple versions and will be kept in database. This is how I write the search (simplified): scope = Invoice.scoped({ :joins => [:disclaimer] }) scope = scope.scoped :conditions => ["Invoice.invoice_num = ?", "#{params[:num]}"] scope = scope.scoped :conditions => ["Disclaimer.body LIKE ?", "%#{params[:text]}%"] However, the above search will search again all versions of the disclaimer. How can I limit the search to only the last disclaimer (i.e. the version integer is the maximum). Please note: Invoice does not keep the version number. New disclaimers will be added to disclaimer table and keep old versions.

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• NHibernate, each property is filled with a different select statement

  - by Eitan

  I'm retrieving a list of nhibernate entites which have relationships to other tables/entities. I've noticed instead of NHibernate performing JOINS and populating the properties, it retrieves the entity and then calls a select for each property. For example if a user can have many roles and I retrieve a user from the DB, Nhibernate retrieves the user and then populates the roles with another select statement. The problem is that I want to retrieve oh let's say a list of products which have various many-to-many relationships and relationships to items which have their own relationships. In the end I'm left with over a thousand DB calls to retrieve a list of 30 products. Thanks. I've also set default lazy loading to false because whenever I save the list of entities to a session, I get an error when trying to retrieve it on another page: LazyInitializationException: could not initialize proxy If anybody could shed any light I would truly appreciate it. Thanks. Eitan

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• OracleDataAdapter returns no rows, but the query string works in SQLDeveloper

  - by belzebu

  visual studion 2008 oracle db 11.1.0.7 oracle client for .NET I have a relatively simple query, that selects the rows from across multiple tables (up to 4) using joins. OracleDataAdapter returns no rows for the only dataset's table, but if I copy and paste that query in SQLDeveloper then I get the desired results. I can get the data from other tables using the adapter with no problem, but it seems like it struggles with the bit longer selection query (string length is ~ 300 (not that much at all)) Connection string for the connection is 100% correct. Any ideas? thank you...

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• Int PK inner join Vs Guid PK inner Join on SQL Server. Execution plan.

  - by bigb

  I just did some testing for Int PK join Vs Guid PK. Tables structure and number of records looking like that: Performance of CRUD operations using EF4 are pretty similar in both cases. As we know Int PK has better performance rather than strings. So SQL server execution plan with INNER JOINS are pretty different Here is an execution plan. As i understand according with execution plan from attached image Int join has better performance because it is taking less resources for Clustered index scan and it is go in two ways, am i right? May be some one may explain this execution plan in more details?

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• Updating rows using "in" operator in "where" clause

  - by doublep

  Hi. I stumbled upon SQL behavior I don't understand. I needed to update several rows in a table at once; started with just finding them: SELECT * FROM some_table WHERE field1 IN (SELECT ...) This returned a selection of about 60 rows. Now I was pretty confident I got the subquery right, so I modified the first part only: UPDATE some_table SET field2 = some_value WHERE field1 IN (SELECT ...) In other words, this was exactly as the first query after the WHERE. However, it resulted in 0 rows updated, whereas I would expect those 60. Note that the statement above would change field2, i.e. I verified that some_value was not present in the selected rows. The subquery was a modestly complicated SQL piece with 2 (different) tables, 1 view, joins and its own WHERE clause. In case this matters, it happened with Oracle Database 10g. So, the question is, why UPDATE didn't touch the rows returned by SELECT?

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• ssrs: one static row matrix, multiple columns will not filter out nulls

  - by pbarton99

  Using a ssrs 2005 matrix client side. I want to list the multiple addresses of one person, hence one row, multiple columns. The Column field is =Fields!StreetName.Value. The data details field is =First(Fields!StreetPrefix.Value) & " " & First(Fields!StreetName.Value). The datasource has a row for each address; however, some rows will have nulls since the datasource is composed of outer joins. The column grouping works, but the first column is always empty, (first 2 rows of datasource are null) addresses appear only after the empty column. I want to filter out nulls on the matrix, but its like the filter is ignored. I have also tried having the dataset return an empty string for a null streetname and setting the filter to =Fields!StreetName.Value != ="" but no difference. What am I missing?

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• What are some "mental steps" a developer must take to begin moving from SQL to NO-SQL (CouchDB, Fath

  - by Byron Sommardahl

  I have my mind firmly wrapped around relational databases and how to code efficiently against them. Most of my experience is with MySQL and SQL. I like many of the things I'm hearing about document-based databases, especially when someone in a recent podcast mentioned huge performance benefits. So, if I'm going to go down that road, what are some of the mental steps I must take to shift from SQL to NO-SQL? If it makes any difference in your answer, I'm a C# developer primarily (today, anyhow). I'm used to ORM's like EF and Linq to SQL. Before ORMs, I rolled my own objects with generics and datareaders. Maybe that matters, maybe it doesn't. Here are some more specific: How do I need to think about joins? How will I query without a SELECT statement? What happens to my existing stored objects when I add a property in my code? (feel free to add questions of your own here)

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• How to optimize an SQL query with many thousands of WHERE clauses

  - by bugaboo

  I have a series of queries against a very mega large database, and I have hundreds-of-thousands of ORs in WHERE clauses. What is the best and easiest way to optimize such SQL queries? I found some articles about creating temporary tables and using joins, but I am unsure. I'm new to serious SQL, and have been cutting and pasting results from one into the next. SELECT doc_id, language, author, title FROM doc_text WHERE language='fr' OR language='es' SELECT doc_id, ref_id FROM doc_ref WHERE doc_id=1234567 OR doc_id=1234570 OR doc_id=1234572 OR doc_id=1234596 OR OR OR ... SELECT ref_id, location_id FROM ref_master WHERE ref_id=098765 OR ref_id=987654 OR ref_id=876543 OR OR OR ... SELECT location_id, location_display_name FROM location SELECT doc_id, index_code, FROM doc_index WHERE doc_id=1234567 OR doc_id=1234570 OR doc_id=1234572 OR doc_id=1234596 OR OR OR x100,000 These unoptimized query can take over 24 hours each. Cheers.

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• How do I find the user that has both a cat and a dog?

  - by brad

  I want to do a search across 2 tables that have a many-to-one relationship, eg class User << ActiveRecord::Base has_many :pets end class Pet << ActiveRecord::Base belongs_to :users end Now let's say I have some data like so users id name 1 Bob 2 Joe 3 Brian pets id user_id animal 1 1 cat 2 1 dog 3 2 cat 4 3 dog What I want to do is create an active record query that will return a user that has both a cat and a dog (i.e. user 1 - Bob). My attempt at this so far is User.joins(:pets).where('pets.animal = ? AND pets.animal = ?','dog','cat') Now I understand why this doesn't work - it's looking for a pet that is both a dog and a cat so returns nothing. I don't know how to modify this to give me the answer I want however. Does anyone have any suggestions? This seems like it should be easy - it doesn't seem like an especially unusual situation.

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• Implementing Tagging using Core Data on the iPhone

  - by Jonathan Penn

  I have an application that uses CoreData and I'm trying to figure out the best way to implement tagging and filtering by tag. For my purposes, if I was doing this in raw SQLite I would only need three tables, tags, item_tags and of course my items table. Then filtering would be as simple as joining between the three tables where only items are related to the given tags. Quite straightforward. But, is there a way to do this in CoreData and utilizing NSFetchedResultsController? It doesn't seem that NSPredicate give you the ability to filter through joins. NSPredicate's aren't full SQL anyway so I'm probably barking up the wrong tree there. I'm trying to avoid reimplementing my app using SQLite without CoreData since I'm enjoying the performance CoreData gives me in other areas. Yes, I did consider (and built a test implementation) diving into the raw SQLite that CoreData generates, but that's not future proof and I want to avoid that, too. Has anyone else tried to tackle tagging/filtering with CoreData in a UITableView with NSFetchedResultsController

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• rails data aggregation

  - by ash34

  Hi, I have to create a hash of the form h[:bill] = ["Billy", "NA", 20, "PROJ_A"] by login where 20 is the cumulative number of hours reported by the login for all task transactions returned by the query where each login has multiple reported transactions. Did I do this in a bad way or this seems alright. h = Hash.new Task.find_each(:include => [:user], :joins => :user, :conditions => ["from_date >= ? AND from_date <= ? AND category = ?", Date.today - 30, Date.today + 30, 'PROJ1']) do |t| h[t.login.intern] = [t.user.name, 'NA', h[t.login.intern].nil? ? (t.hrs_per_day * t.num_days) : h[t.login.intern][2] + (t.hrs_day * t.workdays), t.category] end Also if I have to aggregate this data not just by login but login and category how do I accomplish this? thanks, ash

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• How do I replace NOT EXISTS with JOIN?

  - by YelizavetaYR

  I've got the following query: select distinct a.id, a.name from Employee a join Dependencies b on a.id = b.eid where not exists ( select * from Dependencies d where b.id = d.id and d.name = 'Apple' ) and exists ( select * from Dependencies c where b.id = c.id and c.name = 'Orange' ); I have two tables, relatively simple. The first Employee has an id column and a name column The second table Dependencies has 3 column, an id, an eid (employee id to link) and names (apple, orange etc). the data looks like this Employee table looks like this id | name ----------- 1 | Pat 2 | Tom 3 | Rob 4 | Sam Dependencies id | eid | Name -------------------- 1 | 1 | Orange 2 | 1 | Apple 3 | 2 | Strawberry 4 | 2 | Apple 5 | 3 | Orange 6 | 3 | Banana As you can see Pat has both Orange and Apple and he needs to be excluded and it has to be via joins and i can't seem to get it to work. Ultimately the data should only return Rob

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• Rails 3 Join Question for Votes Table

  - by Dex

  I have a table posts and a polymorphic table votes. The votes table looks like this: create_table :votes do |t| t.references :user # user_id t.vote # the vote value t.references :votable # votable_type and votable_id end I want to list all posts that the user has not yet voted on. Right now I'm basically taking all the posts they've already voted on and subtracting that from the entire set of posts. It works but it's not very convenient as I currently have it. def self.where_not_voted_on_by(user) sql = "SELECT P.* FROM posts P LEFT OUTER JOIN (" sql << where_voted_on_by(user).to_sql sql << ") ALREADY_VOTED_FOR ON P.id = ALREADY_VOTED_FOR.id WHERE (user_id is null)" puts sql resultset = connection.select_all(sql) results = [] resultset.each do |r| results << Post.new(r) end results end def self.where_voted_on_by(user) joins(:votes.outer).where("user_id = #{user.id}").select("posts.*, votes.user_id") end

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• How do I find where id does not match any of an array?

  - by Nick5a1

  I have a Workout model that has and belongs to many Equipment models. I have an array of some Equipment IDs. I want to find all Workouts that don't have any Equipment assigned that matches any of the array of Equipment IDs. So, if my array = [2,3,5] I want to find all workouts where the assigned equipment ids does not include 2, 3 or 5. EDIT: Workout.joins(:equipment).where("equipment.id not in(?)",[2,3,5]).uniq Assuming five instances of Equipment, the code above returns workouts with equipment.ids 1 and 4 (good), but also returns partial matches for example Workouts with equipment.id = [1,2], [1,2,3].

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• SQL Query over three different tables

  - by choise

  i got three tables CATS id name ------------------------------ 1 category1 2 category2 3 category3 4 category4 PRODUCT id name ------------------------------ 1 product1 2 product2 ZW-CAT-PRODUCT id_cats id_product ------------------------------ 1 1 3 1 4 2 now i want to get my products and their categories product1 => category1,category3 product2 => category4 is there a way to get this array (or object or something) with one mysql query? i tried a bit with JOINS, but it seems thats this is not exactly what i need, or? currently i'm using 3 querys (i think thats too much). any suggestions?

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• MySQL Query WHERE Including CASE or IF?

  - by handfix

  Strange problem. My Query looks like SELECT DISTINCT ID, `etcetc`, `if/elses over muliple joined tables` FROM table1 AS `t1` # some joins, eventually unrelated in that context WHERE # some standard where statements, they work/ CASE WHEN `t1`.`field` = "foo" THEN (`t1`.`anOtherField` != 123 AND `t1`.`anOtherField` != 456 AND `t1`.`anOtherOtherField` != "some String") WHEN `t1`.`field` = "bar" THEN `t1`.`aSecondOtherField` != 12345 END #ORDER BY CASE etc. Standard Stuff Apperantly MySQL returns a wrong rowcount and I think my problem is in the logic of the WHERE ... CASE statement. Maybe with the brackets? Maybe I should go for operator OR and not AND? Should my the second WHEN include brackets also, even when I only compare one field? Should I use IF and not CASE? Basically I want to exclude some rows with specific values IF theres a specific value in field foo or bar I would try that all out, but it takes a huge amount of time to complete that query... :(

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• Seeking free ODBC database optimization tool for non-experts

  - by mawg

  I'm a database n00b and am reading as many books as I can. I have been given responsibility for an ODBC tool where the databases were designed by a hardware engineer with some VB experience - which made him a s/w guru in the small firm at that time. Things are running slowly and I suspect that the db could have been designed better. I hope to learn enough to use Explain/Describe, etc maybe add some indices, but, in the meantime, is there any free for commercial use tool which can examine an ODBC database and suggest improvements. I'm just talking about db schema here, but maybe I should also be looking at optimizing Selects with Joins? Is there a tool for that? ODBC compliant.

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• django modeling

  - by SledgehammerPL

  Concept: Drinks are made of components. E.g. 10ml of Vodka. In some receipt the component is very particular (10ml of Finlandia Vodka), some not (10 ml of ANY Vodka). I wonder how to model a component to solve this problem - on stock I have particular product, which can satisfy more requirements. The model for now is: class Receipt(models.Model): name = models.CharField(max_length=128) (...) components = models.ManyToManyField(Product, through='ReceiptComponent') def __unicode__(self): return self.name class ReceiptComponent(models.Model): product = models.ForeignKey(Product) receipt = models.ForeignKey(Receipt) quantity = models.FloatField(max_length=9) unit = models.ForeignKey(Unit) class Admin: pass def __unicode__(self): return unicode(self.quantity!=0 and self.quantity or '') + ' ' + unicode(self.unit) + ' ' + self.product.genitive class Product(models.Model): name = models.CharField(max_length = 128) (...) class Admin: pass def __unicode__(self): return self.name class Stock(Store): products = models.ManyToManyField(Product) class Admin: pass def __unicode__(self): return self.name I think about making some table which joins real product (on stock) with abstract product (receiptcomponent). But maybe there's easy solution?

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• Oracle curcular join sometimes give duplicates, but sometimes does not

  - by Kaushik

  By mistake I wrote a query like this: select * from a,b,c where a.col=b.col and b.col2=c.col2 and c.col3=a.col4 So there is a circular join here. Now the thing is sometimes this query returns duplicate result, sometimes it returns unique(correct) results. I am trying to understand why it does not give duplicate results always. Also if circular joins are not allowed, how come Oracle does not throw an error. EDIT: This is the actual query. After reading ti carefully, I am not sure anymore if this is a circular join or not.It does not seem so...but why I get duplicates only sometime? select * from a,b,c,d where a.col=b.col and b.col=c.col and c.col2=d.col2 and d.col2 =a.col2

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• mysql multiple where and inner join query combination

  - by bandhunt

  I'm a little lost as how to run two mysql queries as one(return one result set to be sorted etc). I understand how to do multiple JOINS but need to combine the below which is more than just a multiple join - it would include a multiple where etc. 1st query sql = "SELECT s.id, s.song_name FROM `songs` as s INNER JOIN `artists` as a ON s.artist_id = a.id WHERE ((`a`.id = #{search}))" 2nd query sql = "SELECT s.id, s.song_name FROM `songs` as s INNER JOIN `similarments` as si ON s.artist_id = si.artist_id WHERE ((`si`.similar_id = #{search}))" And then run both queries at once so I can ORDER them etc. Or combine them as one big query (maybe put an OR somewhere)? Thanks!

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• web page db query optimisation

  - by morpheous

  I am putting together a web page which is quite 'expensive' in terms of Db hits. I dont want to start optimizing at this stage - though with me trying to hit a deadline, I may end up not optimising at all. Currently the page requires 18 (thats right eighteen) hits to the db. I am already using joins, and some of the queries are UNIONed to minimize the trips to the db. My local dev machine can handle this (page is not slow) however, I feel if I release this into the wild, the number of queries will quickly overwhelm my database (mySQL). I could always use memcache or something similar, but I would much rather continue with my other dev work that needs to be completed before the deadline - at least retrieving the page work, its simply a matter of optimization. My question therefore is - is 18 db queries for a single page retrieval completely outrageous - (i.e. I should put everything on hold and optimize the hell of the retrieval logic), or shall I continue as normal, meet the deadline and release on schedule and see what happens?

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• Repetitive SQL: What does it mean?

  - by Lijo

  Hi In a different post I got a reply that tells about Repetitive SQL. Could you please explain what is Repetitive SQL? http://stackoverflow.com/questions/2657459/sql-code-smells I thought to make it a new post as it is a different subject. The reply says that use of "multiple stored procedures that perform the exact same joins but different filters" can be avoided using VIEWs. Could you please give an example that can only be achieved using repetitive queries, if we are using Stored Proecure? [The same can be achieved without repetition when used VIEWS] Thanks Lijo

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• Rails + simple role system through associative table

  - by user202411

  So I have the Ninja model which has many Hovercrafts through ninja_hovercrafts (which stores the ninja_id and the hovercraft_id). It is of my understanding that this kind of arrangement should be set in a way that the associative table stores only enough information to bind two different classes. But I'd like to use the associative table to work as a very streamlined authorization hub on my application. So i'd also like this table to inform my system if this binding makes the ninja the pilot or co-pilot of a given hovercraft, through a "role" field in the table. My questions are: Is this ugly? Is this normal? Are there methods built into rails that would help me to automagically create Ninjas and Hovercrafts associations WITH the role? For exemple, could I have a nested form to create both ninjas and hcs in a way that the role field in ninjas_hovercrafts would be also filled? If managing my application roles this way isn't a good idea, whats the non-resource heavy alternative (my app is being designed trying to avoid scalability problems such as excessive joins, includes, etc) thank you

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