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• How to avoid Cartesian product in an INNER JOIN query?

  - by flhe

  I have 6 tables, let's call them a,b,c,d,e,f. Now I want to search all the colums (except the ID columns) of all tables for a certain word, let's say 'Joe'. What I did was, I made INNER JOINS over all the tables and then used LIKE to search the columns. INNER JOIN ... ON INNER JOIN ... ON.......etc. WHERE a.firstname ~* 'Joe' OR a.lastname ~* 'Joe' OR b.favorite_food ~* 'Joe' OR c.job ~* 'Joe'.......etc. The results are correct, I get all the colums I was looking for. But I also get some kind of cartesian product, I get 2 or more lines with almost the same results. How can i avoid this? I want so have each line only once, since the results should appear on a web search.

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• Isn't INT more efficient than UNIQUEIDENTIFIER?

  - by ck

  I have a parent table and child table where the columns that join them together are the UNIQUEIDENTIFIER type. The child table has a clustered index on the column that joins it to the parent table (its PK, which is also clustered). I have created a copy of both of these tables but changed the relationship columns to be INTs instead, have rebuilt the indexes so that they are essentially the same structure and can be queried in the same way. When I query for a known 20 records from the parent table, pulling in all the related records from the child tables, I get identical query costs across both, i.e. 50/50 cost for the batches. If this is true, then my giant project to change all of the tables like this appears to be pointless, other than speeding up inserts. Can anyone provide any light on the situation?

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• Rails eager loading

  - by Dimitar Vouldjeff

  HI, I have a Test model, which has_many questions, and Question, which has_many answers... When I make a query for a Test with :include = [:questions, {:questions = :answers}] ActiveRecord makes two more queries to fetch the questions and then to fetch the answers - it doesn`t join them!!! When I do the query with :joins ActiveRecord makes the query, but later when I need the Test.questions or Test.questions.answers ActiveRecord makes again those 2 extra queries!!! And later when I enumerate the questions or answers in the log I see other queries for each object, but it has Cache tag... Is this normal?

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• cakephp and SQL_CALC_FOUND_ROWS

  - by Lizard

  I am trying to add the SQL_CALC_FOUND_ROWS into a query (Please note this isn't for pagination) please note I am trying to add this to a cakePHP query the code I currently have is below: return $this->find('all', array( 'conditions' => $conditions, 'fields'=>array('SQL_CALC_FOUND_ROWS','Category.*','COUNT(`Entity`.`id`) as `entity_count`'), 'joins' => array('LEFT JOIN `entities` AS Entity ON `Entity`.`category_id` = `Category`.`id`'), 'group' => '`Category`.`id`', 'order' => $sort, 'limit'=>$params['limit'], 'offset'=>$params['start'], 'contain' => array('Domain' => array('fields' => array('title'))) )); Note the 'fields'=>array('SQL_CALC_FOUND_ROWS',' this obviously doesn't work as It tries to apply the SQL_CALC_FOUND_ROWS to the table e.g. SELECTCategory.SQL_CALC_FOUND_ROWS, Is there anyway of doing this? Any help would be greatly appreciated, thanks.

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• iPhone Development - Query related records using CoreData

  - by Mustafa

  I have a case where i have three entities with one-to-many and one-to-many relationships: Entity A (Entity B relationhip), Entity B (Entity A relationship, Entity C relationship), Entity C (Entity B relationhip) I have the reference of Entity A, and now i want to fetch all the related Entity C records. How can i do that? (with least amount of code) Edit: Here's another way to put it. Can we perform joins with CoreData. For example, (and this is a very crude example), We have a following entity-relationship: Grand Parent (1)---(m) Parent Parent (1)---(m) Child So, now if i have "Albert" the Grand Parent, and i want to get all his grand children, how can i do that?

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• Counting number of children in hierarchical SQL data

  - by moontear

  for a simple data structure such as so: ID parentID Text Price 1 Root 2 1 Flowers 3 1 Electro 4 2 Rose 10 5 2 Violet 5 6 4 Red Rose 12 7 3 Television 100 8 3 Radio 70 9 8 Webradio 90 For reference, the hierarchy tree looks like this: ID Text Price 1 Root |2 Flowers |-4 Rose 10 | |-6 Red Rose 12 |-5 Violet 5 |3 Electro |-7 Television 100 |-8 Radio 70 |-9 Webradio 90 I'd like to count the number of children per level. So I would get a new column "NoOfChildren" like so: ID parentID Text Price NoOfChildren 1 Root 8 2 1 Flowers 3 3 1 Electro 3 4 2 Rose 10 1 5 2 Violet 5 0 6 4 Red Rose 12 0 7 3 Television 100 0 8 3 Radio 70 1 9 8 Webradio 90 0 I read a few things about hierarchical data, but I somehow get stuck on the multiple inner joins on the parentIDs. Maybe someone could help me out here. moon

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• AppDomain.CurrentDomain.DomainUnload not be raised in Console app

  - by Guy

  I have an assembly that when accessed spins up a single thread to process items placed on a queue. In that assembly I attach a handler to the DomainUnload event: AppDomain.CurrentDomain.DomainUnload += new EventHandler(CurrentDomain_DomainUnload); That handler joins the thread to the main thread so that all items on the queue can complete processing before the application terminates. The problem that I am experiencing is that the DomainUnload event is not getting fired when the console application terminates. Any ideas why this would be? Using .NET 3.5 and C#

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• Feeding a Drill Down Menu with categories, subcategories and subSubcategories from a database

  - by Hassan

  Hi everyone, I have a Drill Down menu and I want to have it gets its elements from a database, I am using php and MySQL and the table (categories) looks like this : http://yfrog.com/jctablehsj I can't figure out how I can extract these information in a way I could put it inside the Drill Down Menu ! I found the recursive method (with LEFT JOINs) and the nested method which I barely understood and again I couldn't apply it to the Drill Down Menu. I found that some people found out a solution with left join and group by but couldn't understand or copy their example ! I would be more than gratefull if you could give me the extact of the query. Thanks a lot for your hard work, Hassan

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• SQL Server Table locks in long query - Solution: NoLock?

  - by Kovu

  a report in my application runs a query that needs between 5 - 15 seconds (constrained to count of rows that will be returned). The query has 8 joins to nearly all main-tables of my application (Customers, sales, units etc). A little tool shows me, that in this time, all those 8 tables are locked with a shared table lock. That means, no update operation will be done in this time. A solution from a friend is, to have every join in the query, which is not mandetory to have 100% correct data (dirty read), with a NoLock, so only 1 of this 8 tables will be locked completly. Is that a good solution? For a report in which 99% of data came from one table, unlock the less prio tables?

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• MsSQL 2005 query performance

  - by Max

  I have the following query: select ............. from //one table and about 20 left joins// where ( ( this_.driverName like 'blah*' or this_.renterName like 'blah*' ) or exists ( select this0__.id as y0_ from ThirdParty this0__ where this0__.name like 'blah*' and this0__.claim_id=this_.id ) ) order by this_.id asc And I have two environment: One with 175 000 records in table "this_" and second with 25 000 records in table "this_". This query works right on 175k database and it works smth about 2 seconds, but on base with 25k this query freezes. and if drop one the folloing item from where clause: ( this_.driverName like 'blah*' or this_.renterName like 'blah*' ) or exists ( select this0__.id as y0_ from ThirdParty this0__ where this0__.name like 'blah*' and this0__.claim_id=this_.id ) query runs normally. How can I to increase performance of this query?

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• Codeigniter: Combining activeRecord with manual queries?

  - by Industrial

  Hi everybody, I've though a bit about the activerecord vs. manual queries in Codeigniter. ActiveRecord is awesome when it's all about standard queries and holds development time really low. However, when there's a need to add some complexity to the queries, the ActiveRecord gets quite complicated to work with. Sub queries or complex joins gives atleast me a lot of headache. Since the current "$this-db-query" -call immediately executes the set query, it can't be combined with normal activeRecord calls. So, what can I do to combine the two methods? Thanks!

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• How to create a custom ADO Multi Dimensional Catalog with no database

  - by Alan Clark

  Does anyone know of an example of how to dynamically define and build ADO MD (ActiveX Data Objects Multidimensional) catalogs and cube definitions with a set of data other than a database? Background: we have a huge amount of data in our application that we export to a database and then query using the usual SQL joins, groups, sums etc to produce reports. The data in the application is originally in objects and arrays. The problem is the amount of data is so large the export can take 2 hours. So I am trying to figure out a good way of querying the objects in memory, either by a custom OLAP algorithm or library, or ADO MD. But I haven't been able to find an example of using ADO MD without a database behind it. We are using Delphi 2010 so would use ADO ActiveX but I imagine the ADO.NET MD is similar. I realize that if the application data was already stored in a database the problem would solve itself. Also if Delphi had LINQ capability I could query the objects and arrays that way.

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• Help with linq to sql compiled query

  - by stackoverflowuser

  Hi I am trying to use compiled query for one of my linq to sql queries. This query contains 5 to 6 joins. I was able to create the compiled query but the issue I am facing is my query needs to check if the key is within a collection of keys passed as input. But compiled queries do not allow passing of collection (since collection can have varying number of items hence not allowed). For instance input to the function is a collection of keys. Say: List<Guid> InputKeys List<SomeClass> output = null; var compiledQuery = CompiledQueries.Compile<DataContext, IQueryable<SomeClass>>( (context) => from a in context.GetTable<A>() where InputKeys.Contains(a.Key) select a); using(var dataContext = new DataContext()) { output = compiledQuery(dataContext).ToList(); } return output; Is there any work around or better way to do the above?

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• SQL constructs translated to OOP

  - by python dude

  As someone who comes from the world of Object Orientation, I find it rather difficult to wrap my head around SQL. Recently, however, I realized that the classical SQL construct select X from Y where Z is basically equivalent to the following OOP construct: List<SomeType> results = db.query(new Matcher<SomeType> () { public boolean match(SomeType candidate) { return ...; // checks condition Z on candidate, returns true for match } }; So my question is: What are the OOP equivalents for other SQL constructs, such as joins?

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• Profiling statements inside a User-Defined Function

  - by Craig Walker

  I'm trying to use SQL Server Profiler (2005) to track down some application performance problems. One of the calls being made is to a table-valued user-defined function. This function wraps a select that joins several tables together. In SQL Server Profiler, the call to the UDF is logged. However, the select that underlies the UDF isn't being logged at all. Because of this, I'm not getting useful data on which tables & indexes are being hit. I'd like to feed this info into the Database Tuning Advisor for some indexing advice. Is there any way (short of unwrapping the queries themselves) to log the tables called by UDFs in Profiler?

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• Many-to-Many Relationships in MySQL

  - by Kaji

  I've been reading up on foreign keys and joins recently, and have been pleasantly surprised that many of the basic concepts are things I'm already putting into practice. For example, with one project I'm currently working on, I'm organizing word lists, and have a table for the sets, like so: `words` Table `word_id` `headword` `category_id` `categories` Table `category_id` `category_name` Now, generally speaking this would be a one-to-many relationship, with several words being placed under a single category with the foreign key category_id. Let's assume for a moment, however, that a user chooses to add another category to a word, making it many-to-many—Is there a way to set up my words table to handle additional categories for words without creating extra columns like category_2, category_3, etc.?

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• Generate Info (wrapper) Class from stored procedure

  - by Adem

  Hello everybody I am in a crucial project and I am trying to speed up the development phase by using codesmith for generating the business class DAL and info class for the tables of my project. There are about 50 tables with relationships parent child many to many and for retrieving data I have to code several inner joins in stored procedures. I have to combine fields from many tables and this makes working with the info class difficult. Is there anyway to generate info class from stored procedures or to be more exact is there a way to parse the result set of the stored procedure and to generate the info class with properties for every column in that result set. Please if anyone can give me some advice and tell me how to achieve this. Best Regards

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• What are appropriate ways to represent relationships between people in a database table?

  - by Emilio

  I've got a table of people - an ID primary key and a name. In my application, people can have 0 or more real-world relationships with other people, so Jack might "work for" Jane and Tom might "replace" Tony and Bob might "be an employee of" Rob and Bob might also "be married to" Mary. What's the best way to represent this in the database? A many to many intersect table? A series of self joins? A relationship table with one row per relationship pair and type, where I insert records for the relationship in both directions?

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• Django and conditional aggregates

  - by piquadrat

  I have two models, authors and articles: class Author(models.Model): name = models.CharField('name', max_length=100) class Article(models.Model) title = models.CharField('title', max_length=100) pubdate = models.DateTimeField('publication date') authors = models.ManyToManyField(Author) Now I want to select all authors and annotate them with their respective article count. That's a piece of cake with Django's aggregates. Problem is, it should only count the articles that are already published. According to ticket 11305 in the Django ticket tracker, this is not yet possible. I tried to use the CountIf annotation mentioned in that ticket, but it doesn't quote the datetime string and doesn't make all the joins it would need. So, what's the best solution, other than writing custom SQL?

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• How to join data frames in R (inner, outer, left, right)?

  - by Dan Goldstein

  Given two data frames df1 = data.frame(CustomerId=c(1:6),Product=c(rep("Toaster",3),rep("Radio",3))) df2 = data.frame(CustomerId=c(2,4,6),State=c(rep("Alabama",2),rep("Ohio",1))) > df1 CustomerId Product 1 Toaster 2 Toaster 3 Toaster 4 Radio 5 Radio 6 Radio > df2 CustomerId State 2 Alabama 4 Alabama 6 Ohio How can I do database style, i.e., sql style, joins? That is, how do I get: An inner join of df1 and df1 An outer join of df1 and df2 A left outer join of df1 and df2 A right outer join of df1 and df2 P.S. IKT-JARQ (I Know This - Just Adding R Questions) Extra credit: How can I do a sql style select statement?

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• Calling sp and Performance strategy.

  - by Costa

  Hi I find my self in a situation where I have to choose between either creating a new sp in database and create the middle layer code. so loose some precious development time. also the procedure is likely to contain some joins. Or use two existing sp(s), the problem of this approach is that I am doing two round trips to database. which can be poor performance especially if I have database in another server. Which approach you will go?, and why? thanks

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• Strange: Planner takes decision with lower cost, but (very) query long runtime

  - by S38

  Facts: PGSQL 8.4.2, Linux I make use of table inheritance Each Table contains 3 million rows Indexes on joining columns are set Table statistics (analyze, vacuum analyze) are up-to-date Only used table is "node" with varios partitioned sub-tables Recursive query (pg = 8.4) Now here is the explained query: WITH RECURSIVE rows AS ( SELECT * FROM ( SELECT r.id, r.set, r.parent, r.masterid FROM d_storage.node_dataset r WHERE masterid = 3533933 ) q UNION ALL SELECT * FROM ( SELECT c.id, c.set, c.parent, r.masterid FROM rows r JOIN a_storage.node c ON c.parent = r.id ) q ) SELECT r.masterid, r.id AS nodeid FROM rows r QUERY PLAN ----------------------------------------------------------------------------------------------------------------------------------------------------------------- CTE Scan on rows r (cost=2742105.92..2862119.94 rows=6000701 width=16) (actual time=0.033..172111.204 rows=4 loops=1) CTE rows -> Recursive Union (cost=0.00..2742105.92 rows=6000701 width=28) (actual time=0.029..172111.183 rows=4 loops=1) -> Index Scan using node_dataset_masterid on node_dataset r (cost=0.00..8.60 rows=1 width=28) (actual time=0.025..0.027 rows=1 loops=1) Index Cond: (masterid = 3533933) -> Hash Join (cost=0.33..262208.33 rows=600070 width=28) (actual time=40628.371..57370.361 rows=1 loops=3) Hash Cond: (c.parent = r.id) -> Append (cost=0.00..211202.04 rows=12001404 width=20) (actual time=0.011..46365.669 rows=12000004 loops=3) -> Seq Scan on node c (cost=0.00..24.00 rows=1400 width=20) (actual time=0.002..0.002 rows=0 loops=3) -> Seq Scan on node_dataset c (cost=0.00..55001.01 rows=3000001 width=20) (actual time=0.007..3426.593 rows=3000001 loops=3) -> Seq Scan on node_stammdaten c (cost=0.00..52059.01 rows=3000001 width=20) (actual time=0.008..9049.189 rows=3000001 loops=3) -> Seq Scan on node_stammdaten_adresse c (cost=0.00..52059.01 rows=3000001 width=20) (actual time=3.455..8381.725 rows=3000001 loops=3) -> Seq Scan on node_testdaten c (cost=0.00..52059.01 rows=3000001 width=20) (actual time=1.810..5259.178 rows=3000001 loops=3) -> Hash (cost=0.20..0.20 rows=10 width=16) (actual time=0.010..0.010 rows=1 loops=3) -> WorkTable Scan on rows r (cost=0.00..0.20 rows=10 width=16) (actual time=0.002..0.004 rows=1 loops=3) Total runtime: 172111.371 ms (16 rows) (END) So far so bad, the planner decides to choose hash joins (good) but no indexes (bad). Now after doing the following: SET enable_hashjoins TO false; The explained query looks like that: QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- CTE Scan on rows r (cost=15198247.00..15318261.02 rows=6000701 width=16) (actual time=0.038..49.221 rows=4 loops=1) CTE rows -> Recursive Union (cost=0.00..15198247.00 rows=6000701 width=28) (actual time=0.032..49.201 rows=4 loops=1) -> Index Scan using node_dataset_masterid on node_dataset r (cost=0.00..8.60 rows=1 width=28) (actual time=0.028..0.031 rows=1 loops=1) Index Cond: (masterid = 3533933) -> Nested Loop (cost=0.00..1507822.44 rows=600070 width=28) (actual time=10.384..16.382 rows=1 loops=3) Join Filter: (r.id = c.parent) -> WorkTable Scan on rows r (cost=0.00..0.20 rows=10 width=16) (actual time=0.001..0.003 rows=1 loops=3) -> Append (cost=0.00..113264.67 rows=3001404 width=20) (actual time=8.546..12.268 rows=1 loops=4) -> Seq Scan on node c (cost=0.00..24.00 rows=1400 width=20) (actual time=0.001..0.001 rows=0 loops=4) -> Bitmap Heap Scan on node_dataset c (cost=58213.87..113214.88 rows=3000001 width=20) (actual time=1.906..1.906 rows=0 loops=4) Recheck Cond: (c.parent = r.id) -> Bitmap Index Scan on node_dataset_parent (cost=0.00..57463.87 rows=3000001 width=0) (actual time=1.903..1.903 rows=0 loops=4) Index Cond: (c.parent = r.id) -> Index Scan using node_stammdaten_parent on node_stammdaten c (cost=0.00..8.60 rows=1 width=20) (actual time=3.272..3.273 rows=0 loops=4) Index Cond: (c.parent = r.id) -> Index Scan using node_stammdaten_adresse_parent on node_stammdaten_adresse c (cost=0.00..8.60 rows=1 width=20) (actual time=4.333..4.333 rows=0 loops=4) Index Cond: (c.parent = r.id) -> Index Scan using node_testdaten_parent on node_testdaten c (cost=0.00..8.60 rows=1 width=20) (actual time=2.745..2.746 rows=0 loops=4) Index Cond: (c.parent = r.id) Total runtime: 49.349 ms (21 rows) (END) - incredibly faster, because indexes were used. Notice: Cost of the second query ist somewhat higher than for the first query. So the main question is: Why does the planner make the first decision, instead of the second? Also interesing: Via SET enable_seqscan TO false; i temp. disabled seq scans. Than the planner used indexes and hash joins, and the query still was slow. So the problem seems to be the hash join. Maybe someone can help in this confusing situation? thx, R.

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• ActiveRecord fundamentally incompatible with composite keys?

  - by stimms

  I have been attempting to use subsonic for a project on which I'm working. All was going quite well until I encountered a link table with a composite primary key. That is a key made up of the primary keys of the two tables it joins. Subsonic failed to recognize both keys which was problematic. I was going to adjust subsonic to support compound keys but I stopped and though "Maybe there is a reason for this". Normally active record relies on a single primary key field for every record, even in link tables. But is this necessary? Should I just give up on active record for this project or continue with my modifications?

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• Query Concatenated Field (using SubSonic)

  - by jwynveen

  Is there a way to query against a concatenated field using MS SQL? For instance, what I want to do is something like: Select FirstName+' '+LastName as FullName from Attendees where FullName like '%Joe Schmoe%' The above doesn't work. What I have found works is: Select * from Attendee where FirstName+' '+LastName like '%Joe Schmoe%' but I can't figure out how to do that using a SubSonic SqlQuery. I have a number of joins and OR statements added dynamically that I don't want to have to write out the sql manually. Any help/ideas?

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• Why might SQL execute more quickly on SQL Server 2000 when NOT using a stored procedure?

  - by Kofi Sarfo

  I could see nothing wrong with the execution plan. Besides, as I understand it, SQL Server 2000 extended many of the performance benefits of stored procedures to all SQL statements by recognising new T-SQL statements against T-SQL statements of existing execution plans (by retaining execution plans for all SQL statements in the procedure cache, not just stored procedure execution plans) It's a fairly straight forward SELECT statement with sensible table joins, no transactions included or linked servers being referenced within the query and WITH (NOLOCK) table hints applied. The stored procedure was created by dbo and the user has all the necessary permissions. So my question is this: What are the likely reasons for a query to take only a few seconds to run but then take several minutes when identical T-SQL is run via a stored procedure?

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