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• Technology Plan - Which tools should I use?

  - by Armadillo

  Hi, Soon, I'll start my own software company. My primary product/solution will be a Billing/Invoice Software. In a near future, I pretend to expand this first module to an ERP. My app should be able to run as a stand-alone application and as a Web-based application (so there will be, probably two GUI for the same Database). My problem, now, is to choose the right tools; I'm talking about what programming language(s) should I use, what kind of database should I choose, and stuff like that. I'm primarily a VB6 programmer, so probably I'll choose the .net framework (vb/c#). But I'm seriously thinking about Java. Java has 2 "pros" that I really like: write once, run anywhere and it is free (I think...). I've been thinking about RIAs too, but I just don't have any substantial feedback about them... Then, I'll need a report tool. Crystal Reports? HTML based Reports? Other? Databases: I'm not sure if I should use SQL-Server Express or PostgreSQL (or other). I'd be happy to hear any comments and advices Thanks

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• Algorithm for optimally choosing actions to perform a task

  - by Jules

  There are two data types: tasks and actions. An action costs a certain time to complete, and a set of tasks this actions consists of. A task has a set of actions, and our job is to choose one of them. So: class Task { Set<Action> choices; } class Action { float time; Set<Task> dependencies; } For example the primary task could be "Get a house". The possible actions for this task: "Buy a house" or "Build a house". The action "Build a house" costs 10 hours and has the dependencies "Get bricks" and "Get cement", etcetera. The total time is the sum of all the times of the actions required to perform. We want to choose actions such that the total time is minimal. Note that the dependencies can be diamond shaped. For example "Get bricks" could require "Get a car" (to transport the bricks) and "Get cement" would also require a car. Even if you do "Get bricks" and "Get cement" you only have to count the time it takes to get a car once. Note also that the dependencies can be circular. For example "Money" - "Job" - "Car" - "Money". This is no problem for us, we simply select all of "Money", "Job" and "Car". The total time is simply the sum of the time of these 3 things. Mathematical description: Let actions be the chosen actions. valid(task) = ?action ? task.choices. (action ? actions ? ?tasks ? action.dependencies. valid(task)) time = sum {action.time | action ? actions} minimize time subject to valid(primaryTask)

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• ruby on rails one-to-many relationship

  - by fenec

  I would like to model a betting system relationship using the power of rails. so lets start with doing something very simple modelling the relationship from a user to a bet.i would like to have a model bet with 2 primary keys. here are my migrations enter code here class CreateBets < ActiveRecord::Migration def self.up create_table :bets do |t| t.integer :user_1_id t.integer :user_2_id t.integer :amount t.timestamps end end def self.down drop_table :bets end end class CreateUsers < ActiveRecord::Migration def self.up create_table :users do |t| t.string :name t.timestamps end end def self.down drop_table :users end end the models enter code here class Bet < ActiveRecord::Base belongs_to :user_1,:class_name=:User belongs_to :user_2,:class_name=:User end class User < ActiveRecord::Base has_many :bets, :foreign_key =:user_1) has_many :bets, :foreign_key =:user_2) end when i test here in the console my relationships I got an error enter code here u1=User.create :name="aa" = # u2=User.create :name="bb" = # b=Bet.create(:user_1=u1,:user_2=u2) *****error***** QUESTIONS: 1 How do I define the relationships between these tables correctly? 2 are there any conventions to name the attributes (ex:user_1_id...) thank you for your help

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• How do I make the manifest available during a Maven/Surefire unittest run "mvn test" ?

  - by Ernst de Haan

  How do I make the manifest available during a Maven/Surefire unittest run "mvn test" ? I have an open-source project that I am converting from Ant to Maven, including its unit tests. Here's the project source repository with the Maven project: http://github.com/znerd/logdoc My question pertains to the primary module, called "base". This module has a unit test that tests the behaviour of the static method getVersion() in the class org.znerd.logdoc.Library. This method returns: Library.class.getPackage().getImplementationVersion() The getImplementationVersion() method returns a value of a setting in the manifest file. So far, so good. I have tested this in the past and it works well, as long as the manifest is indeed available on the classpath at the path META-INF/MANIFEST.MF (either on the file system or inside a JAR file). Now my challenge is that the manifest file is not available when I run the unit tests: mvn test Surefire runs the unit tests, but my unit test fails with a mesage indicating that Library.getVersion() returned null. When I want to check the JAR, I find that it has not even been generated. Maven/Surefire runs the unit tests against the classes, before the resources are added to the classpath. So can I either run the unit tests against the JAR (implicitly requiring the JAR to be generated first) or can I make sure the resources (including the manifest file) are generated/copied under target/classes before the unit tests are run? Note that I use Maven 2.2.0, Java 1.6.0_17 on Mac OS X 10.6.2, with JUnit 4.8.1.

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• Would anybody recommend learning J/K/APL?

  - by ozan

  I came across J/K/APL a few months ago while working my way through some project euler problems, and was intrigued, to say the least. For every elegant-looking 20 line python solution I produced, there'd be a gobsmacking 20 character J solution that ran in a tenth of the time. I've been keen to learn some basic J, and have made a few attempts at picking up the vocabulary, but have found the learning curve to be quite steep. To those who are familiar with these languages, would you recommend investing some time to learn one (I'm thinking J in particular)? I would do so more for the purpose of satisfying my curiosity than for career advancement or some such thing. Some personal circumstances to consider, if you care to: I love mathematics, and use it daily in my work (as a mathematician for a startup) but to be honest I don't really feel limited by the tools that I use (like python + NumPy) so I can't use that excuse. I have no particular desire to work in the finance industry, which seems to be the main port of call for K users at least. Plus I should really learn C# as a next language as it's the primary language where I work. So practically speaking, J almost definitely shouldn't be the next language I learn. I'm reasonably familiar with MATLAB so using an array-based programming language wouldn't constitute a tremendous paradigm shift. Any advice from those familiar with these languages would be much appreciated.

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• SQL Server INSERT ... SELECT Statement won't parse

  - by Jim Barnett

  I am getting the following error message with SQL Server 2005 Msg 120, Level 15, State 1, Procedure usp_AttributeActivitiesForDateRange, Line 18 The select list for the INSERT statement contains fewer items than the insert list. The number of SELECT values must match the number of INSERT columns. I have copy and pasted the select list and insert list into excel and verified there are the same number of items in each list. Both tables an additional primary key field with is not listed in either the insert statement or select list. I am not sure if that is relevant, but suspicious it may be. Here is the source for my stored procedure: CREATE PROCEDURE [dbo].[usp_AttributeActivitiesForDateRange] ( @dtmFrom DATETIME, @dtmTo DATETIME ) AS BEGIN SET NOCOUNT ON; DECLARE @dtmToWithTime DATETIME SET @dtmToWithTime = DATEADD(hh, 23, DATEADD(mi, 59, DATEADD(s, 59, @dtmTo))); -- Get uncontested DC activities INSERT INTO AttributedDoubleClickActivities ([Time], [User-ID], [IP], [Advertiser-ID], [Buy-ID], [Ad-ID], [Ad-Jumpto], [Creative-ID], [Creative-Version], [Creative-Size-ID], [Site-ID], [Page-ID], [Country-ID], [State Province], [Areacode], [OS-ID], [Domain-ID], [Keyword], [Local-User-ID], [Activity-Type], [Activity-Sub-Type], [Quantity], [Revenue], [Transaction-ID], [Other-Data], Ordinal, [Click-Time], [Event-ID]) SELECT [Time], [User-ID], [IP], [Advertiser-ID], [Buy-ID], [Ad-ID], [Ad-Jumpto], [Creative-ID], [Creative-Version], [Creative-Size-ID], [Site-ID], [Page-ID], [Country-ID], [State Province], [Areacode], [OS-ID], [Domain-ID], [Keyword], [Local-User-ID] [Activity-Type], [Activity-Sub-Type], [Quantity], [Revenue], [Transaction-ID], [Other-Data], REPLACE(Ordinal, '?', '') AS Ordinal, [Click-Time], [Event-ID] FROM Activity_Reports WHERE [Time] BETWEEN @dtmFrom AND @dtmTo AND REPLACE(Ordinal, '?', '') IN (SELECT REPLACE(Ordinal, '?', '') FROM Activity_Reports WHERE [Time] BETWEEN @dtmFrom AND @dtmTo EXCEPT SELECT CONVERT(VARCHAR, TripID) FROM VisualSciencesActivities WHERE [Time] BETWEEN @dtmFrom AND @dtmTo); END GO

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• SCD2 + Merge Statement + MSSQL

  - by Nev_Rahd

  I am trying work out with MERGE statment to Insert / Update Dimension Table of Type SCD2 My source is a Table var to Merge with Dimension table. My Merget statement is throwing an error as: The target table 'DM.DATA_ERROR.ERROR_DIMENSION' of the INSERT statement cannot be on either side of a (primary key, foreign key) relationship when the FROM clause contains a nested INSERT, UPDATE, DELETE, or MERGE statement. Found reference constraint 'FK_ERROR_DIMENSION_to_AUDIT_CreatedBy'. My Merge Statement: DECLARE @DATAERROROBJECT AS [ERROR_DIMENSION] INSERT INTO DM.DATA_ERROR.ERROR_DIMENSION SELECT ERROR_CODE, DATA_STREAM_ID, [ERROR_SEVERITY], DATA_QUALITY_RATING, ERROR_LONG_DESCRIPTION, ERROR_DESCRIPTION, VALIDATION_RULE, ERROR_TYPE, ERROR_CLASS, VALID_FROM, VALID_TO, CURR_FLAG, CREATED_BY_AUDIT_SK, UPDATED_BY_AUDIT_SK FROM (MERGE DM.DATA_ERROR.ERROR_DIMENSION ED USING @DATAERROROBJECT OBJ ON(ED.ERROR_CODE = OBJ.ERROR_CODE AND ED.DATA_STREAM_ID = OBJ.DATA_STREAM_ID) WHEN NOT MATCHED THEN INSERT VALUES( OBJ.ERROR_CODE ,OBJ.DATA_STREAM_ID ,OBJ.[ERROR_SEVERITY] ,OBJ.DATA_QUALITY_RATING ,OBJ.ERROR_LONG_DESCRIPTION ,OBJ.ERROR_DESCRIPTION ,OBJ.VALIDATION_RULE ,OBJ.ERROR_TYPE ,OBJ.ERROR_CLASS ,GETDATE() ,'9999-12-13' ,'Y' ,1 ,1 ) WHEN MATCHED AND ED.CURR_FLAG = 'Y' AND ( ED.[ERROR_SEVERITY] <> OBJ.[ERROR_SEVERITY] OR ED.[DATA_QUALITY_RATING] <> OBJ.[DATA_QUALITY_RATING] OR ED.[ERROR_LONG_DESCRIPTION] <> OBJ.[ERROR_LONG_DESCRIPTION] OR ED.[ERROR_DESCRIPTION] <> OBJ.[ERROR_DESCRIPTION] OR ED.[VALIDATION_RULE] <> OBJ.[VALIDATION_RULE] OR ED.[ERROR_TYPE] <> OBJ.[ERROR_TYPE] OR ED.[ERROR_CLASS] <> OBJ.[ERROR_CLASS] ) THEN UPDATE SET ED.CURR_FLAG = 'N', ED.VALID_TO = GETDATE() OUTPUT $ACTION ACTION_OUT, OBJ.ERROR_CODE ERROR_CODE, OBJ.DATA_STREAM_ID DATA_STREAM_ID, OBJ.[ERROR_SEVERITY] [ERROR_SEVERITY], OBJ.DATA_QUALITY_RATING DATA_QUALITY_RATING, OBJ.ERROR_LONG_DESCRIPTION ERROR_LONG_DESCRIPTION, OBJ.ERROR_DESCRIPTION ERROR_DESCRIPTION, OBJ.VALIDATION_RULE VALIDATION_RULE, OBJ.ERROR_TYPE ERROR_TYPE, OBJ.ERROR_CLASS ERROR_CLASS, GETDATE() VALID_FROM, '9999-12-31' VALID_TO, 'Y' CURR_FLAG, 555 CREATED_BY_AUDIT_SK, 555 UPDATED_BY_AUDIT_SK ) AS MERGE_OUT WHERE MERGE_OUT.ACTION_OUT = 'UPDATE'; What am i doing wrong ?

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• Postgre database ignoring created index ?!

  - by drasto

  I have an Postgre database and a table called my_table. There are 4 columns in that table (id, column1, column2, column3). The id column is primary key, there are no other constrains or indexes on columns. The table has about 200000 rows. I want to print out all rows which has value of column column2 equal(case insensitive) to 'value12'. I use this: SELECT * FROM my_table WHERE column2 = lower('value12') here is the execution plan for this statement(result of set enable_seqscan=on; EXPLAIN SELECT * FROM my_table WHERE column2 = lower('value12')): Seq Scan on my_table (cost=0.00..4676.00 rows=10000 width=55) Filter: ((column2)::text = 'value12'::text) I consider this to be to slow so I create an index on column column2 for better prerformance of searches: CREATE INDEX my_index ON my_table (lower(column2)) Now I ran the same select: SELECT * FROM my_table WHERE column2 = lower('value12') and I expect it to be much faster because it can use index. However it is not faster, it is as slow as before. So I check the execution plan and it is the same as before(see above). So it still uses sequential scen and it ignores the index! Where is the problem ?

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• Rails uploaded file blank

  - by Ceilingfish

  Hi chaps, I'm trying to upload a file to the server using a HTTP multipart form in rails, and for some reason it's turning up blank at the other end. I can see it being received in the rails log thusly: Processing Admin::HeadlinesController#update (for 127.0.0.1 at 2010-03-08 12:26:13) [PUT] Parameters: {"commit"=>"Save changes", "action"=>"update", "_method"=>"put", "authenticity_token"=>"mK70XRk5gOPUwXOcNboT/4K8PD9RBM7GqCOlEUKZwcA=", "headline"=>{"position"=>"1", "location"=>"primary", "attachment_id"=>"13", "headline_content"=>"questionnaires", "article_id"=>"3", "image"=>#<File:/tmp/RackMultipart20100308-63211-1vym9nj-0>}, "id"=>"140", "controller"=>"admin/headlines"} But if I have a look in /tmp/RackMultipart20100308-63211-1vym9nj-0 the file is blank. Am I right in thinking that this should be the file that I uploaded? I'm running Phusion Passenger 2.2.7 on Apache 2.2.13, with ruby 1.8.7 and rails 2.3.5, on OSX 10.6.2

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• I need to speed up a function. Should I use cython, ctypes, or something else?

  - by Peter Stewart

  I'm having a lot of fun learning Python by writing a genetic programming type of application. I've had some great advice from Torsten Marek, Paul Hankin and Alex Martelli on this site. The program has 4 main functions: generate (randomly) an expression tree. evaluate the fitness of the tree crossbreed mutate As all of generate, crossbreed and mutate call 'evaluate the fitness'. it is the busiest function and is the primary bottleneck speedwise. As is the nature of genetic algorithms, it has to search an immense solution space so the faster the better. I want to speed up each of these functions. I'll start with the fitness evaluator. My question is what is the best way to do this. I've been looking into cython, ctypes and 'linking and embedding'. They are all new to me and quite beyond me at the moment but I look forward to learning one and eventually all of them. The 'fitness function' needs to compare the value of the expression tree to the value of the target expression. So it will consist of a postfix evaluator which will read the tree in a postfix order. I have all the code in python. I need advice on which I should learn and use now: cython, ctypes or linking and embedding. Thank you.

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• Ordering by a max or a min from another table

  - by Paul Tomblin

  I have a table that consists of a unique id, and a few other attributes. It holds "schedules". Then I have another table that holds a list of all the times each schedule has or will "fire". This isn't the exact schema, but it's close: create table schedule ( id varchar(40) primary key, attr1 int, attr2 varchar(20) ); create table schedule_times ( id varchar(40) foreign key schedule(id), fire_date date ); I want to query the schedule table, getting the attributes and the next and previous fire_dates, in Java, sometimes ordering on one of the attributes, but sometimes ordering on either previous fire_date or the next fire_date. Ordering by the attributes is easy, I just stick an "order by" into the string while I'm building my prepared statement. I'm not even sure how to go about selecting the last fire_date and the next one in a single query - I know that I can find the next fire_date for a given id by doing a SELECT min(fire_date) FROM schedule_times WHERE id = ? AND fire_date > sysdate; and the similar thing for previous fire_date using max() and fire_date < sysdate. I'm just drawing a blank on how to incorporate that into a single select from the schedule so I can get both next and previous fire_date in one shot, and also how to order by either of those attributes.

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• Do COM Dll References Require Manual Disposal? If so, How?

  - by Drew

  I have written some code in VB that verifies that a particular port in the Windows Firewall is open, and opens one otherwise. The code uses references to three COM DLLs. I wrote a WindowsFirewall class, which Imports the primary namespace defined by the DLLs. Within members of the WindowsFirewall class I construct some of the types defined by the DLLs referenced. The following code isn't the entire class, but demonstrates what I am doing. Imports NetFwTypeLib Public Class WindowsFirewall Public Shared Function IsFirewallEnabled as Boolean Dim icfMgr As INetFwMgr icfMgr = CType(System.Activator.CreateInstance(Type.GetTypeFromProgID("HNetCfg.FwMgr")), INetFwMgr) Dim profile As INetFwProfile profile = icfMgr.LocalPolicy.CurrentProfile Dim fIsFirewallEnabled as Boolean fIsFirewallEnabled = profile.FirewallEnabled return fIsFirewallEnabled End Function End Class I do not reference COM DLLs very often. I have read that unmanaged code may not be cleaned up by the garbage collector and I would like to know how to make sure that I have not introduced any memory leaks. Please tell me (a) if I have introduced a memory leak, and (b) how I may clean it up. (My theory is that the icfMgr and profile objects do allocate memory that remains unreleased until after the application closes. I am hopeful that setting their references equal to nothing will mark them for garbage collection, since I can find no other way to dispose of them. Neither one implements IDisposable, and neither contains a Finalize method. I suspect they may not even be relevant here, and that both of those methods of releasing memory only apply to .Net types.)

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• Using an ORM with a database that has no defined relationships?

  - by Ahmad

  Consider a database(MSSQL 2005) that consists of 100+ tables which have primary keys defined to a certain degree. There are 'relationships' between tables, however these are not enforced with foreign key constraints. Consider the following simplified example of typical types of tables I am dealing with. The are clear relations between the User and City and Province tables. However, they key issues is the inconsistent data types in the tables and naming conventions. User: UserRowId [int] PK Name [varchar(50)] CityId [smallint] ProvinceRowId [bigint] City: CityRowId [bigint] PK CityDescription [varchar(100)] Province: ProvinceId [int] PK ProvinceDesc [varchar(50)] I am considering a rewrite of the application (in ASP.net MVC) that uses this data source as is similar in design to MVC storefront. However I am going through a proof of concept phase and this is one of the stumbling blocks I have come across. What are my options in terms of ORM choice that can be easily used and why? Should I even be considering an ORM? (The reason I ask this is that most explanations and tutorials all work with relatively cleanly designed existing databases, or newly created ones when compared to mine. I am thus having a very hard time trying to find a way forward with this problem) There is a huge amount of existing SQL queries, would a datamappper(eg IBatis.net) be more suitable since we could easily modify them to work and reuse the investment already made? I have found this question on SO which indicates to me that an ORM can be used - however I get the impression that this a question of mapping? Note: at the moment, the object model is not clearly defined as it was non-existent. The existing system pretty much did almost everything in SQL or consisted of overly complicated, and numerous queries to complete fucntionality. I am pretty much a noob and have zero experience around ORMs and MVC - so this an awesome learning curve I am on.

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• Storing float numbers as strings in android database

  - by sandis

  So I have an app where I put arbitrary strings in a database and later extract them like this: Cursor DBresult = myDatabase.query(false, Constant.DATABASE_NOTES_TABLE_NAME, new String[] {"myStuff"}, where, null, null, null, null, null); DBresult.getString(0); This works fine in all cases except for when the string looks like a float number, for example "221.123123123". After saving it to the database I can extract the database to my computer and look inside it with a DB-viewer, and the saved number is correct. However, when using cursor.getString() the string "221.123" is returned. I cant for the life of me understand how I can prevent this. I guess I could do a cursor.getDouble() on every single string to see if this gives a better result, but that feels sooo ugly and inefficient. Any suggestions? Cheers, edit: I just made a small test program. This program prints "result: 123.123", when I would like it to print "result: 123.123123123" SQLiteDatabase database = openOrCreateDatabase("databas", Context.MODE_PRIVATE, null); database.execSQL("create table if not exists tabell (nyckel string primary key);"); ContentValues value = new ContentValues(); value.put("nyckel", "123.123123123"); database.insert("tabell", null, value); Cursor result = database.query("tabell", new String[]{"nyckel"}, null, null, null, null, null); result.moveToFirst(); Log.d("TAG","result: " + result.getString(0));

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• Hibernate saveorUpdate method problem

  - by umesh awasthi

  Hi all, i am trying to work on with Hibernate (Database side for first time) and some how struck in choosing best possible way to use saveOrUpdate or Save.Update i have a destination POJO class and its other attributes which needs to be updated along with the Destination entity. i am getting an XML file to be imported and i am using the following code to update/save the destination entity along with its attribute classes. try{ getSessionFactory().getCurrentSession().beginTransaction(); getSessionFactory().getCurrentSession().saveOrUpdate(entity); getSessionFactory().getCurrentSession().getTransaction().commit(); } catch(Exception e){ getSessionFactory().getCurrentSession().getTransaction().rollback(); } finally{ getSessionFactory().close(); } everything is working fine untill i am using the same session instance.but later on when i am using the same XML file to update the destination PO for certain attributes it giving me the following error. SEVERE: Duplicate entry 'MNLI' for key 'DESTINATIONID' 9 Jan, 2011 4:58:11 PM org.hibernate.event.def.AbstractFlushingEventListener performExecutions SEVERE: Could not synchronize database state with session org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:94) at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:275) at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:114) at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:109) at org.hibernate.jdbc.AbstractBatcher.prepareBatchStatement(AbstractBatcher.java:244) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2242) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2678) at org.hibernate.action.EntityInsertAction.execute(EntityInsertAction.java:79) i am using UUID as primary key for the Destination table and in destination table i have a destination id which is unique.but i can understand that in the secodn case hibernate is not able to find if there is already an entry for the same destination in the DB and trying to execute insert statement rather than update. one possible solution is i can user destinationid to check if there is already a destination inplace with the given id and based on the results i can issue save or update command. my question is can this be achieve by any other good way..? Thanks in advance

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• How to index a table with a Type 2 slowly changing dimension for optimal performance

  - by The Lazy DBA

  Suppose you have a table with a Type 2 slowly-changing dimension. Let's express this table as follows, with the following columns: * [Key] * [Value1] * ... * [ValueN] * [StartDate] * [ExpiryDate] In this example, let's suppose that [StartDate] is effectively the date in which the values for a given [Key] become known to the system. So our primary key would be composed of both [StartDate] and [Key]. When a new set of values arrives for a given [Key], we assign [ExpiryDate] to some pre-defined high surrogate value such as '12/31/9999'. We then set the existing "most recent" records for that [Key] to have an [ExpiryDate] that is equal to the [StartDate] of the new value. A simple update based on a join. So if we always wanted to get the most recent records for a given [Key], we know we could create a clustered index that is: * [ExpiryDate] ASC * [Key] ASC Although the keyspace may be very wide (say, a million keys), we can minimize the number of pages between reads by initially ordering them by [ExpiryDate]. And since we know the most recent record for a given key will always have an [ExpiryDate] of '12/31/9999', we can use that to our advantage. However... what if we want to get a point-in-time snapshot of all [Key]s at a given time? Theoretically, the entirety of the keyspace isn't all being updated at the same time. Therefore for a given point-in-time, the window between [StartDate] and [ExpiryDate] is variable, so ordering by either [StartDate] or [ExpiryDate] would never yield a result in which all the records you're looking for are contiguous. Granted, you can immediately throw out all records in which the [StartDate] is greater than your defined point-in-time. In essence, in a typical RDBMS, what indexing strategy affords the best way to minimize the number of reads to retrieve the values for all keys for a given point-in-time? I realize I can at least maximize IO by partitioning the table by [Key], however this certainly isn't ideal. Alternatively, is there a different type of slowly-changing-dimension that solves this problem in a more performant manner?

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• Excessive use of Inner Join for more than 3 tables

  - by Archangel08

  Good Day, I have 4 tables on my DB (not the actual name but almost similar) which are the ff: employee,education,employment_history,referrence employee_id is the name of the foreign key from employee table. Here's the example (not actual) data: **Employee** ID Name Birthday Gender Email 1 John Smith 08-15-2014 Male [email protected] 2 Jane Doe 00-00-0000 Female [email protected] 3 John Doe 00-00-0000 Male [email protected] **Education** Employee_ID Primary Secondary Vocation 1 Westside School Westshore H.S SouthernBay College 2 Eastside School Eastshore H.S NorthernBay College 3 Northern School SouthernShore H.S WesternBay College **Employment_History** Employee_ID WorkOne StartDate Enddate 1 StarBean Cafe 12-31-2012 01-01-2013 2 Coffebucks Cafe 11-01-2012 11-02-2012 3 Latte Cafe 01-02-2013 04-05-2013 Referrence Employee_ID ReferrenceOne Address Contact 1 Abraham Lincoln Lincoln Memorial 0000000000 2 Frankie N. Stein Thunder St. 0000000000 3 Peter D. Pan Neverland Ave. 0000000000 NOTE: I've only included few columns though the rest are part of the query. And below are the codes I've been working on for 3 consecutive days: $sql=mysql_query("SELECT emp.id,emp.name,emp.birthday,emp.pob,emp.gender,emp.civil,emp.email,emp.contact,emp.address,emp.paddress,emp.citizenship,educ.employee_id,educ.elementary,educ.egrad,educ.highschool,educ.hgrad,educ.vocational,educ.vgrad,ems.employee_id,ems.workOne,ems.estartDate,ems.eendDate,ems.workTwo,ems.wstartDate,ems.wendDate,ems.workThree,ems.hstartDate,ems.hendDate FROM employee AS emp INNER JOIN education AS educ ON educ.employee_id='emp.id' INNER JOIN employment_history AS ems ON ems.employee_id='emp.id' INNER JOIN referrence AS ref ON ref.employee_id='emp.id' WHERE emp.id='$id'"); Is it okay to use INNER JOIN this way? Or should I modify my query to get the results that I wanted? I've also tried to use LEFT JOIN but still it doesn't return anything .I didn't know where did I go wrong. You see, as I have thought, I've been using the INNER JOIN in correct manner, (since it was placed before the WHILE CLAUSE). So I couldn't think of what could've possible went wrong. Do you guys have a suggestion? Thanks in advance.

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• What's the most efficient query?

  - by Aaron Carlino

  I have a table named Projects that has the following relationships: has many Contributions has many Payments In my result set, I need the following aggregate values: Number of unique contributors (DonorID on the Contribution table) Total contributed (SUM of Amount on Contribution table) Total paid (SUM of PaymentAmount on Payment table) Because there are so many aggregate functions and multiple joins, it gets messy do use standard aggregate functions the the GROUP BY clause. I also need the ability to sort and filter these fields. So I've come up with two options: Using subqueries: SELECT Project.ID AS PROJECT_ID, (SELECT SUM(PaymentAmount) FROM Payment WHERE ProjectID = PROJECT_ID) AS TotalPaidBack, (SELECT COUNT(DISTINCT DonorID) FROM Contribution WHERE RecipientID = PROJECT_ID) AS ContributorCount, (SELECT SUM(Amount) FROM Contribution WHERE RecipientID = PROJECT_ID) AS TotalReceived FROM Project; Using a temporary table: DROP TABLE IF EXISTS Project_Temp; CREATE TEMPORARY TABLE Project_Temp (project_id INT NOT NULL, total_payments INT, total_donors INT, total_received INT, PRIMARY KEY(project_id)) ENGINE=MEMORY; INSERT INTO Project_Temp (project_id,total_payments) SELECT `Project`.ID, IFNULL(SUM(PaymentAmount),0) FROM `Project` LEFT JOIN `Payment` ON ProjectID = `Project`.ID GROUP BY 1; INSERT INTO Project_Temp (project_id,total_donors,total_received) SELECT `Project`.ID, IFNULL(COUNT(DISTINCT DonorID),0), IFNULL(SUM(Amount),0) FROM `Project` LEFT JOIN `Contribution` ON RecipientID = `Project`.ID GROUP BY 1 ON DUPLICATE KEY UPDATE total_donors = VALUES(total_donors), total_received = VALUES(total_received); SELECT * FROM Project_Temp; Tests for both are pretty comparable, in the 0.7 - 0.8 seconds range with 1,000 rows. But I'm really concerned about scalability, and I don't want to have to re-engineer everything as my tables grow. What's the best approach?

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• creating matrix with probabilities

  - by John Chan

  Hi all, I want to generate a matrix of NxN to test some code that I have where each row contains floats as the elements and has to add up to 1 (i.e. a row with a set of probabilities). Where it gets tricky is that I want to make sure that randomly some of the elements should be 0 (in fact most of the elements should be 0 except for some random ones to be the probabilities). I need the probabilities to be 1/m where m is the number of elements that are not 0 within a single row. I tried to think of ways to output this, but essentially I would need this stored in a C++ array. So even if I output to a file I would still have the issue of not having it in array as I need it. At the end of it all I need that array because I want to generate a Market Matrix file. I found an implementation in C++ to take an array and convert it to the market matrix file, so this is what I am basing my findings on. My input for the rest of the code takes in this market matrix file so I need that to be the primary form of output. The language does not matter, I just want to generate the file at the end (I found a way mmwrite and mmread in python as well) Please help, I am stuck and not really sure how to implement this.

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• [PHP] Kohana-v3 ORM parent relationship

  - by VDVLeon

  Hi all, I just started with the version 3 of the Kohana Framework. I have worked a little with the $_has_many etc. Now I have the table pages. The primary key is pageID. The table has a column called parentPageID. Now I want to make a ORM model who, when accesed like this $page->parent->find() returns the page identified by parentPageID. I have the following already: // Settings protected $_table_name = 'pages'; protected $_primary_key = 'pageID'; protected $_has_one = array( 'parent' => array( 'model' => 'page', 'foreign_key' => 'parentPageID', ), ); But that does not work, it simply returns the first page from the table. Last query says this: SELECT `pages`.* FROM `pages` ORDER BY `pages`.`pageID` ASC LIMIT 1 Does somebody know how to solve this? I know this can: $parent = $page->parent->find($page->parentPageID); but it must be and can be cleaner (I think).

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• Creating an appropriate index for a frequently used query in SQL Server

  - by Slauma

  In my application I have two queries which will be quite frequently used. The Where clauses of these queries are the following: WHERE FieldA = @P1 AND (FieldB = @P2 OR FieldC = @P2) and WHERE FieldA = @P1 AND FieldB = @P2 P1 and P2 are parameters entered in the UI or coming from external datasources. FieldA is an int and highly on-unique, means: only two, three, four different values in a table with say 20000 rows FieldB is a varchar(20) and is "almost" unique, there will be only very few rows where FieldB might have the same value FieldC is a varchar(15) and also highly distinct, but not as much as FieldB FieldA and FieldB together are unique (but do not form my primary key, which is a simple auto-incrementing identity column with a clustered index) I'm wondering now what's the best way to define an index to speed up specifically these two queries. Shall I define one index with... FieldB (or better FieldC here?) FieldC (or better FieldB here?) FieldA ... or better two indices: FieldB FieldA and FieldC FieldA Or are there even other and better options? What's the best way and why? Thank you for suggestions in advance!

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• Using NULLs in matchup table

  - by TomWilsonFL

  I am working on the accounting portion of a reservation system (think limo company). In the system there are multiple objects that can either be paid or submit a payment. I am tracking all of these "transactions" in three tables called: tx, tx_cc, and tx_ch. tx generates a new tx_id (for transaction ID) and keeps the information about amount, validity, etc. Tx_cc and tx_ch keep the information about the credit card or check used, respectively, which link to other tables (credit_card and bank_account among others). This seems fairly normalized to me, no? Now here is my problem: The payment transaction can take place for a myriad of reasons. Either a reservation is being paid for, a travel agent that booked a reservation is being paid, a driver is being paid, etc. This results in multiple tables, one for each of the entities: agent_tx, driver_tx, reservation_tx, etc. They look like this: CREATE TABLE IF NOT EXISTS `driver_tx` ( `tx_id` int(10) unsigned zerofill NOT NULL, `driver_id` int(11) NOT NULL, `reservation_id` int(11) default NULL, `reservation_item_id` int(11) default NULL, PRIMARY KEY (`tx_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; Now this transaction is for a driver, but could be applied to an individual item on the reservation or the entire reservation overall. Therefore I demand either reservation_id OR reservation_item_id to be null. In the future there may be other things which a driver is paid for, which I would also add to this table, defaulting to null. What is the rule on this? Opinion? Obviously I could break this out into MANY three column tables, but the amount of OUTER JOINing needed seems outrageous. Your input is appreciated. Peace, Tom

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• Can I clone an IQueryable in linq? For UNION purposes?

  - by user169867

  I have a table of WorkOrders. The table has a PrimaryWorker & PrimaryPay field. It also has a SecondaryWorker & SecondaryPay field (which can be null). I wish to run 2 very similar queries & union them so that it will return a Worker Field & Pay field. So if a single WorkOrder record had both the PrimaryWorker and SecondaryWorker field populated I would get 2 records back. The "where clause" part of these 2 queries is very similar and long to construct. Here's a dummy example var q = ctx.WorkOrder.Where(w => w.WorkDate >= StartDt && w.WorkDate <= EndDt); if(showApprovedOnly) { q = q.Where(w => w.IsApproved); } //...more filters applied Now I also have a search flag called "hideZeroPay". If that's true I don't want to include the record if the worker was payed $0. But obviously for 1 query I need to compare the PrimaryPay field and in the other I need to compare the SecondaryPay field. So I'm wondering how to do this. Can I clone my base query "q" and make a primary & secondary worker query out of it and then union those 2 queries together? I'd greatly appreciate an example of how to correctly handle this. Thanks very much for any help.

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• JoinColumn name not used in sql

  - by Vladimir

  Hi! I have a problem with mapping many-to-one relationship without exact foreign key constraint set in database. I use OpenJPA implementation with MySql database, but the problem is with generated sql scripts for insert and select statements. I have LegalEntity table which contains RootId column (among others). I also have Address table which has LegalEntityId column which is not nullable, and which should contain values referencing LegalEntity's "RootId" column, but without any database constraint (foreign key) set. Address entity is mapped: @Entity @Table(name="address") public class Address implements Serializable { ... @ManyToOne(fetch=FetchType.LAZY, optional=false) @JoinColumn(referencedColumnName="RootId", name="LegalEntityId", nullable=false, insertable=true, updatable=true, table="LegalEntity") public LegalEntity getLegalEntity() { return this.legalEntity; } } SELECT statement (when fetching LegalEntity's addresses) and INSERT statment are generated: SELECT t0.Id, .., t0.LEGALENTITY_ID FROM address t0 WHERE t0.LEGALENTITY_ID = ? ORDER BY t0.Id DESC [params=(int) 2] INSERT INTO address (..., LEGALENTITY_ID) VALUES (..., ?) [params=..., (int) 2] If I omit table attribute from mentioned statements are generated: SELECT t0.Id, ... FROM address t0 INNER JOIN legalentity t1 ON t0.LegalEntityId = t1.RootId WHERE t1.Id = ? ORDER BY t0.Id DESC [params=(int) 2] INSERT INTO address (...) VALUES (...) [params=...] So, LegalEntityId is not included in any of the statements. Is it possible to have relationship based on such referencing (to column other than primary key, without foreign key in database)? Is there something else missing? Thanks in advance.

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• VB.NET Update Access Database with DataTable

  - by sinDizzy

  I've been perusing some hep forums and some help books but cant seem to get my head wrapped around this. My task is to read data from two text files and then load that data into an existing MS Access 2007 database. So here is what i'm trying to do: Read data from first text file and for every line of data add data to a DataTable using CarID as my unique field. Read data from second text file and look for existing CarID in DataTable if exists update that row. If it doesnt exist add a new row. once im done push the contents of the DataTable to the database. What i have so far: Dim sSQL As String = "SELECT * FROM tblCars" Dim da As New OleDb.OleDbDataAdapter(sSQL, conn) Dim ds As New DataSet da.Fill(ds, "CarData") Dim cb As New OleDb.OleDbCommandBuilder(da) 'loop read a line of text and parse it out. gets dd, dc, and carId 'create a new empty row Dim dsNewRow As DataRow = ds.Tables("CarData").NewRow() 'update the new row with fresh data dsNewRow.Item("DriveDate") = dd dsNewRow.Item("DCode") = dc dsNewRow.Item("CarNum") = carID 'about 15 more fields 'add the filled row to the DataSet table ds.Tables("CarData").Rows.Add(dsNewRow) 'end loop 'update the database with the new rows da.Update(ds, "CarData") Questions: In constructing my table i use "SELECT * FROM tblCars" but what if that table has millions of records already. Is that not a waste of resources? Should i be trying something different if i want to update with new records? Once Im done with the first text file i then go to my next text file. Whats the best approach here: To First look for an existing record based on CarNum or to create a second table and then merge the two at the end? Finally when the DataTable is done being populated and im pushing it to the database i want to make sure that if records already exist with three primary fields (DriveDate, DCode, and CarNum) that they get updated with new fields and if it doesn't exist then those records get appended. Is that possible with my process? tia AGP

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