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• Big-O for calculating all routes from GPS data

  - by HH

  A non-critical GPS module use lists because it needs to be modifiable, new routes added, new distances calculated, continuos comparisons. Well so I thought but my team member wrote something I am very hard to get into. His pseudo code int k =0; a[][] <- create mapModuleNearbyDotList -array //CPU O(n) for(j = 1 to n) // O(nlog(m)) for(i =1 to n) for(k = 1 to n) if(dot is nearby) adj[i][j]=min(adj[i][j], adj[i][k] + adj[k][j]); His ideas transformations of lists to tables His worst case time complexity is O(n^3), where n is number of elements in his so-called table. Exception to the last point with Finite structure: O(mlog(n)) where n is number of vertices and m is the amount of neighbour vertices. Questions about his ideas why to waste resources to transform constantly-modified lists to table? Fast? only point where I to some extent agree but cannot understand the same upper limits n for each for-loops -- perhaps he supposed it circular why does the code take O(mlog(n)) to proceed in time as finite structure? The term finite may be wrong, explicit?

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• What is the fastest way to find duplicates in multiple BIG txt files?

  - by user2950750

  I am really in deep water here and I need a lifeline. I have 10 txt files. Each file has up to 100.000.000 lines of data. Each line is simply a number representing something else. Numbers go up to 9 digits. I need to (somehow) scan these 10 files and find the numbers that appear in all 10 files. And here comes the tricky part. I have to do it in less than 2 seconds. I am not a developer, so I need an explanation for dummies. I have done enough research to learn that hash tables and map reduce might be something that I can make use of. But can it really be used to make it this fast, or do I need more advanced solutions? I have also been thinking about cutting up the files into smaller files. To that 1 file with 100.000.000 lines is transformed into 100 files with 1.000.000 lines. But I do not know what is best: 10 files with 100 million lines or 1000 files with 1 million lines? When I try to open the 100 million line file, it takes forever. So I think, maybe, it is just too big to be used. But I don't know if you can write code that will scan it without opening. Speed is the most important factor in this, and I need to know if it can be done as fast as I need it, or if I have to store my data in another way, for example, in a database like mysql or something. Thank you in advance to anybody that can give some good feedback.

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• Using group_by with fields_for and accepts_nested_attributes_for

  - by Derek

  I have a the following rails models: class Release < ActiveRecord::Base has_many :release_questionnaires, :dependent => :destroy accepts_nested_attributes_for :release_questionnaires ... end class class ReleaseQuestionnaire < ActiveRecord::Base belongs_to :release belongs_to :milestone ... end class In my view code, I have the following form. <% form_for @release, ... do |f| %> ... <table class="questionnaires"> <% f.fields_for :release_questionnaires, @release.release_questionnaires.sort_by{|ra| ra.questionnaire.name} do |builder| %> ... <% end %> </table> <% end %> This works and allows me to view and edit the questionnaires as desired. However, I have an additional requirement to break the questionnaires out into their own tables grouped by the milestone they are associated to, rather than in a single table. It appears as though the group_by method is design to accomplish this, but I cannot get it to work as desired inside the tag. It may be that I'm missing something obvious, as I am a beginner... Any help is appreciated.

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• Optimizing T-SQL where an array would be nice

  - by Polatrite

  Alright, first you'll need to grab a barf bag. I've been tasked with optimizing several old stored procedures in our database. This SP does the following: 1) cursor loops through a series of "buildings" 2) cursor loops through a week, Sunday-Saturday 3) has a huge set of IF blocks that are responsible for counting how many Objects of what Types are present in a given building Essentially what you'll see in this code block is that, if there are 5 objects of type #2, it will increment @Type_2_Objects_5 by 1. IF @Number_Type_1_Objects = 0 BEGIN SET @Type_1_Objects_0 = @Type_1_Objects_0 + 1 END IF @Number_Type_1_Objects = 1 BEGIN SET @Type_1_Objects_1 = @Type_1_Objects_1 + 1 END IF @Number_Type_1_Objects = 2 BEGIN SET @Type_1_Objects_2 = @Type_1_Objects_2 + 1 END IF @Number_Type_1_Objects = 3 BEGIN SET @Type_1_Objects_3 = @Type_1_Objects_3 + 1 END [... Objects_4 through Objects_20 for Type_1] IF @Number_Type_2_Objects = 0 BEGIN SET @Type_2_Objects_0 = @Type_2_Objects_0 + 1 END IF @Number_Type_2_Objects = 1 BEGIN SET @Type_2_Objects_1 = @Type_2_Objects_1 + 1 END IF @Number_Type_2_Objects = 2 BEGIN SET @Type_2_Objects_2 = @Type_2_Objects_2 + 1 END IF @Number_Type_2_Objects = 3 BEGIN SET @Type_2_Objects_3 = @Type_2_Objects_3 + 1 END [... Objects_4 through Objects_20 for Type_2] In addition to being extremely hacky (and limited to a quantity of 20 objects), it seems like a terrible way of handling this. In a traditional language, this could easily be solved with a 2-dimensional array... objects[type][quantity] += 1; I'm a T-SQL novice, but since writing stored procedures often uses a lot of temporary tables (which could essentially be a 2-dimensional array) I was wondering if someone could illuminate a better way of handling a situation like this with two dynamic pieces of data to store. Requested in comments: The columns are simply Number_Type_1_Objects, Number_Type_2_Objects, Number_Type_3_Objects, Number_Type_4_Objects, Number_Type_5_Objects, and CurrentDateTime. Each row in the table represents 5 minutes. The expected output is to figure out what percentage of time a given quantity of objects is present throughout each day. Sunday - Object Type 1 0 objects - 69 rows, 5:45, 34.85% 1 object - 85 rows, 7:05, 42.93% 2 objects - 44 rows, 3:40, 22.22% On Sunday, there were 0 objects of type 1 for 34.85% of the day. There was 1 object for 42.93% of the day, and 2 objects for 22.22% of the day. Repeat for each object type.

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• EF4 POCO Not Updating Navigation Property On Save

  - by Gavin Draper

  I'm using EF4 with POCO objects the 2 tables are as follows Service ServiceID, Name, StatusID Status StatusID, Name The POCO objects look like this Service ServiceID, Status, Name Status StatusID, Name With Status on the Service object being a Navigation Property and of type Status. In my Service Repository I have a save method that takes a service objects attaches it to the context and calls save. This works fine for the service, but if the status for that service has been changed it does not get updated. My Save method looks like this public static void SaveService(Service service) { using (var ctx = Context.CreateContext()) { ctx.AttachModify("Services", service); ctx.AttachTo("Statuses",service.Status); ctx.SaveChanges(); } } The AttachModify method attaches an object to the context and sets it to modified it looks like this public void AttachModify(string entitySetName, object entity) { if (entity != null) { AttachTo(entitySetName, entity); SetModified(entity); } } public void SetModified(object entity) { ObjectStateManager.ChangeObjectState(entity, EntityState.Modified); } If I look at a SQL profile its not even including the navigation property in the update for the service table, it never touches the StatusID. Its driving me crazy. Any idea what I need to do to force the Navigation Property to update?

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• Mapping relationships from multiple databases in NHibernate

  - by mannish

  I have a multi-database application configured with NHibernate. The entities that correspond to tables from each database are in their own separate assemblies (an assembly per database if you will). I have a need/desire to relate an entity from one database to an entity of another database. Everything up to this point works as I want it to (the application handles multiple session factories, etc.). The relationship I want is many-to-one, but in reality my application only cares about one side of the relationship (for reasons that aren't relevant). The relevant entities are Project and PMProject, where a Project HAS A PMProject. When I map the many-to-one, I get the following error: NHibernate.MappingException: An association from the table PROJECTS refers to an unmapped class: SDMS.PPRM.PMProject The Project mapping itself reads (ignore the funky column naming; it's an Oracle db): <many-to-one name="PMProject" class="SDMS.PPRM.PMProject" column="PM_PROJECT_ID" cascade="none" /> In the class attribute, I'm referencing the appropriate assembly, but I get that error which seems to tell me it simply can't find the mapping file for PMProject. But that file exists (it's set as embedded resource), the session factory instantiation works without fail; so I'm at a loss on how to tell the Project mapping how/where to look for the appropriate mapping. Is there something I'm missing? A better way to go about this? Thanks in advance.

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• Dynamic evaluation of a table column within an insert before trigger

  - by Tim Garver

  HI All, I have 3 tables, main, types and linked. main has an id column and 32 type columns. types has id, type linked has id, main_id, type_id I want to create an insert before trigger on the main table. It needs to compare its 32 type columns to the values in the types table if the main table column has an 'X' for its value and insert the main_id and types_id into the linked table. i have done a lot of searching, and it looks like a prepared statement would be the way to go, but i wanted to ask the experts. The issue, is i dont want to write 32 IF statements, and even if i did, i need to query the types table to get the ID for that type, seems like a huge waist of resources. Ideally i want to do this inside of my trigger: BEGIN DECLARE @types results_set -- (not sure if this is a valid type); -- (iam sure my loop syntax is all wrong here)... SET @types = (select * from types) for i=0;i<types.records;i++ { IF NEW.[i.type] = 'X' THEN insert into linked (main_id,type_id) values (new.ID, i.id); END IF; } END; Anyway, This is what i was hoping to do, maybe there is a way to dynamically set the field name inside of a results loop, but i cant find a good example of this. Thanks in advance Tim

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• Is there a reason why SSIS significantly slows down after a few minutes?

  - by Mark

  I'm running a fairly substantial SSIS package against SQL 2008 - and I'm getting the same results both in my dev environment (Win7-x64 + SQL-x64-Developer) and the production environment (Server 2008 x64 + SQL Std x64). The symptom is that initial data loading screams at between 50K - 500K records per second, but after a few minutes the speed drops off dramatically and eventually crawls embarrasingly slowly. The database is in Simple recovery model, the target tables are empty, and all of the prerequisites for minimally logged bulk inserts are being met. The data flow is a simple load from a RAW input file to a schema-matched table (i.e. no complex transforms of data, no sorting, no lookups, no SCDs, etc.) The problem has the following qualities and resiliences: Problem persists no matter what the target table is. RAM usage is lowish (45%) - there's plenty of spare RAM available for SSIS buffers or SQL Server to use. Perfmon shows buffers are not spooling, disk response times are normal, disk availability is high. CPU usage is low (hovers around 25% shared between sqlserver.exe and DtsDebugHost.exe) Disk activity primarily on TempDB.mdf, but I/O is very low (< 600 Kb/s) OLE DB destination and SQL Server Destination both exhibit this problem. To sum it up, I expect either disk, CPU or RAM to be exhausted before the package slows down, but instead its as if the SSIS package is taking an afternoon nap. SQL server remains responsive to other queries, and I can't find any performance counters or logged events that betray the cause of the problem. I'll gratefully reward any reasonable answers / suggestions.

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• PostgreSQL: return select count(*) from old_ids;

  - by Alexander Farber

  Hello, please help me with 1 more PL/pgSQL question. I have a PHP-script run as daily cronjob and deleting old records from 1 main table and few further tables referencing its "id" column: create or replace function quincytrack_clean() returns integer as $BODY$ begin create temp table old_ids (id varchar(20)) on commit drop; insert into old_ids select id from quincytrack where age(QDATETIME) > interval '30 days'; delete from hide_id where id in (select id from old_ids); delete from related_mks where id in (select id from old_ids); delete from related_cl where id in (select id from old_ids); delete from related_comment where id in (select id from old_ids); delete from quincytrack where id in (select id from old_ids); return select count(*) from old_ids; end; $BODY$ language plpgsql; And here is how I call it from the PHP script: $sth = $pg->prepare('select quincytrack_clean()'); $sth->execute(); if ($row = $sth->fetch(PDO::FETCH_ASSOC)) printf("removed %u old rows\n", $row['count']); Why do I get the following error? SQLSTATE[42601]: Syntax error: 7 ERROR: syntax error at or near "select" at character 9 QUERY: SELECT select count(*) from old_ids CONTEXT: SQL statement in PL/PgSQL function "quincytrack_clean" near line 23 Thank you! Alex

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• UITableView cell appearance update not working - iPhone

  - by Jack Nutkins

  I have this piece of code which I'm using to set the alpha and accessibility of one of my tables cells dependent on a value stored in user defaults: - (void) viewDidAppear:(BOOL)animated{ [self reloadTableData]; } - (void) reloadTableData { if ([[userDefaults objectForKey:@"canDeleteReceipts"] isEqualToString:@"0"]) { NSIndexPath *path = [NSIndexPath indexPathForRow:0 inSection:8]; UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:path]; cell.contentView.alpha = 0.2; cell.userInteractionEnabled = NO; } else { NSIndexPath *path = [NSIndexPath indexPathForRow:0 inSection:8]; UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:path]; cell.contentView.alpha = 1; cell.userInteractionEnabled = YES; } if ([[userDefaults objectForKey:@"canDeleteMileages"] isEqualToString:@"0"]) { NSIndexPath *path = [NSIndexPath indexPathForRow:1 inSection:8]; UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:path]; cell.contentView.alpha = 0.2; cell.userInteractionEnabled = NO; } else { NSIndexPath *path = [NSIndexPath indexPathForRow:1 inSection:8]; UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:path]; cell.contentView.alpha = 1; cell.userInteractionEnabled = YES; } if ([[userDefaults objectForKey:@"canDeleteAll"] isEqualToString:@"0"]) { NSIndexPath *path = [NSIndexPath indexPathForRow:2 inSection:8]; UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:path]; cell.contentView.alpha = 0.2; cell.userInteractionEnabled = NO; NSLog(@"In Here"); } else { NSIndexPath *path = [NSIndexPath indexPathForRow:2 inSection:8]; UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:path]; cell.contentView.alpha = 1; cell.userInteractionEnabled = YES; } } The value stored in userDefaults is '0' so the cell in section 8 row 2 should be greyed out and disabled, however this doesn't happen and the cell is still selectable with an alpha of 1... The log statement 'In Here' is called so it seems to be executing the right code, but that code doesn't seem to be doing anything. Can anyone explain what I've done wrong? Thanks, Jack

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• how does MySQL implement the "group by"?

  - by user188916

  I read from the MySQL Reference Manual and find that when it can take use of index,it just do index scan,other it will create tmp tables and do things like filesort. And I also read from other article that the "Group By" result will sort by group by columns by default,if "order by null" clause added,it won't don filesort. The difference can be found from the "explain ..." clause. so my problem is:what is the difference between "group by" clause that with "order by null" and which doesn't have? I try to use profiling to see what mysql do on the background,and only see result like: result for group clause without order by null: |preparing | 0.000016 | | Creating tmp table | 0.000048 | | executing | 0.000009 | | Copying to tmp table | 0.000109 | **| Sorting result | 0.000023 |** | Sending data | 0.000027 | result for clause with "order by null": preparing | 0.000016 | | Creating tmp table | 0.000052 | | executing | 0.000009 | | Copying to tmp table | 0.000114 | | Sending data | 0.000028 | So I guess what MySQL do when the "order by null" added,it does not use filesort algorithm,maybe when it creates the tmp table,it uses index as well,and then use the index to do group by operation,when completed,it just read result from the table rows and does not sort the result. But my original opinion is that MySQL can use quicksort to sort the items and then do group by,so the result will be sorted as well. Any opinion appreciated,thanks.

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• entity framework insert bug

  - by tmfkmoney

  I found a previous question which seemed related but there's no resolution and it's 5 months old so I've opened my own version. http://stackoverflow.com/questions/1545583/entity-framework-inserting-new-entity-via-objectcontext-does-not-use-existing-e When I insert records into my database with the following it works fine for a while and then eventually it starts inserting null values in the referenced field. This typically happens after I do an update on my model from the database although not always after I do an update. I'm using a MySQL database for this. I have debugged the code and the values are being set properly before the save event. They're just not getting inserted properly. I can always fix this issue by re-creating the model without touching any of my code. I have to recreate the entire model, though. I can't just dump the relevant tables and re-add them. This makes me think it doesn't have anything to do with my code but something with the entity framework. Does anyone else have this problem and/or solved it? using (var db = new MyModel()) { var stocks = from record in query let ticker = record.Ticker select new { company = db.Companies.FirstOrDefault(c => c.ticker == ticker), price = Convert.ToDecimal(record.Price), date_stamp = Convert.ToDateTime(record.DateTime) }; foreach (var stock in stocks) { if (stock.company != null) { var price = new StockPrice { Company = stock.company, price = stock.price, date_stamp = stock.date_stamp }; db.AddToStockPrices(price); } } db.SaveChanges(); }

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• how to create aro using dbAcl using console

  - by Praveen kalal

  hi i am using cakephp for my project but whille creating acl using command promt. when i run the following command cake schema run create DbAcl it genrate three tables in database. but after puting the following code in users_controller.php. and this command. cake acl view aro it dont create aros. function index() { $aro =& $this->Acl->Aro; //pr($aro); exit; //Here's all of our group info in an array we can iterate through $groups = array( 0 => array( 'alias' => 'admins' ), 1 => array( 'alias' => 'guests' ), 2 => array( 'alias' => 'mangers' ) ); //Iterate and create ARO groups foreach($groups as $data) { //Remember to call create() when saving in loops... $aro->create(); //Save data $aro->save($data); } }

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• How to use MySQL geospatial extensions with spherical geometries

  - by Joshua

  Hi Everyone, I would like to store thousands of latitude/longitude points in a MySQL db. I was successful at setting up the tables and adding the data using the geospatial extensions where the column 'coord' is a Point(lat, lng). Problem: I want to quickly find the 'N' closest entries to latitude 'X' degrees and longitude 'Y' degrees. Since the Distance() function has not yet been implemented, I used GLength() function to calculate the distance between (X,Y) and each of the entries, sorting by ascending distance, and limiting to 'N' results. The problem is that this is not calculating shortest distance with spherical geometry. Which means if Y = 179.9 degrees, the list of closest entries will only include longitudes of starting at 179.9 and decreasing even though closer entries exist with longitudes increasing from -179.9. How does one typically handle the discontinuity in longitude when working with spherical geometries in databases? There has to be an easy solution to this, but I must just be searching for the wrong thing because I have not found anything helpful. Should I just forget the GLength() function and create my own function for calculating angular separation? If I do this, will it still be fast and take advantage of the geospatial extensions? Thanks! josh UPDATE: This is exactly what I am describing above. However, it is only for SQL Server. Apparently SQL Server has a Geometry and Geography datatypes. The geography does exactly what I need. Is there something similar in MySQL?

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• nHibernate storage of an object with self referencing many children and many parents

  - by AdamC

  I have an object called MyItem that references children in the same item. How do I set up an nhibernate mapping file to store this item. public class MyItem { public virtual string Id {get;set;} public virtual string Name {get;set;} public virtual string Version {get;set;} public virtual IList<MyItem> Children {get;set;} } So roughly the hbm.xml would be: <class name="MyItem" table="tb_myitem"> <id name="Id" column="id" type="String" length="32"> <generator class="uuid.hex" /> </id> <property name="Name" column="name" /> <property name="Version" column="version" /> <bag name="Children" cascade="all-delete-orphan" lazy="false"> <key column="children_id" /> <one-to-many class="MyItem" not-found="ignore"/> </bag> </class> This wouldn't work I don't think. Perhaps I need to create another class, say MyItemChildren and use that as the Children member and then do the mapping in that class? This would mean having two tables. One table holds the MyItem and the other table holds references from my item. NOTE: A child item could have many parents.

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• How do I rescue a small portion of data from a SQL Server database backup?

  - by Greg

  I have a live database that had some data deleted from it and I need that data back. I have a very recent copy of that database that has already been restored on another machine. Unrelated changes have been made to the live database since the backup, so I do not want to wipe out the live database with a full restore. The data I need is small - just a dozen rows - but those dozen rows each have a couple rows from other tables with foreign keys to it, and those couple rows have god knows how many rows with foreign keys pointing to them, so it would be complicated to restore by hand. Ideally I'd be able to tell the backup copy of the database to select the dozen rows I need, and the transitive closure of everything that they depend on, and everything that depends on them, and export just that data, which I can then import into the live database without touching anything else. What's the best approach to take here? Thanks. Everyone has mentioned sp_generate_inserts. When using this, how do you prevent Identity columns from messing everything up? Do you just turn IDENTITY INSERT on?

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• CakePHP: Need help using saveField to update a fields in a belongsTo model

  - by afrisch

  I am trying to update a password into two different models/tables in CakePHP. I can update it fine in the parent model, but not the second model. Models: Users (hasOne GameProfile) PK=id Gameprofiles (belongsTo User) FK=user_id Here is a stripped down version of my function in the Users_controller.php: function updatepass() { if (!empty($this->data)) { $this->User->id = $this->Auth->user('id'); $this->User->saveField('sha1password', $this->Auth->password($this->data['User']['newpass'])); $this->User->Gameprofile->saveField('plainpassword', $this->data['User']['newpass']); } } When I execute the function, the users table is updated fine. But the gameprofile table is not updated, rather Cake does an insert. SQL Query Log: 1195 Query UPDATE `users` SET `sha1password` = 'e9443e9f5e1a07832aad1b2f84de1a666daf89b5' WHERE `users`.`id` = 30 1195 Query INSERT INTO `gameprofiles` (`plainpassword`) VALUES ('abc') Is there a way to get CakePHP to do an update using saveField on a model with a belongsTo attribute? I've tried various ways to refer to user_id before executing the second saveField, but just can't seem to find the winning combination. Any help is greatly appreciated!

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• iBatis how to solve a more complex N+1 problem

  - by Alvin

  I have a database that is similar to the following: create table Store(storeId) create table Staff(storeId_fk, staff_id, staffName) create table Item(storeId_fk, itme_id, itemName) The Store table is large. And I have create the following java bean public class Store { List<Staff> myStaff List<Item> myItem .... } public class Staff { ... } public class Item { ... } My question is how can I use iBatis's result map to EFFICIENTLY map from the tables to the java object? I tried: <resultMap id="storemap" class="my.example.Store"> <result property="myStaff" resultMap="staffMap"/> <result property="myItem" result="itemMap"/> </resultMap> (other maps omitted) But it's way too slow since the Store table is VERY VERY large. I tried to follow the example in Clinton's developer guide for the N+1 solution, but I cannot warp my mind around how to use the "groupBy" for an object with 2 list... Any help is appreciated!

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• Select return dynamic columns

  - by Ascalonian

  I have two tables: Standards and Service Offerings. A Standard can have multiple Service Offerings. Each Standard can have a different number of Service Offerings associated to it. What I need to be able to do is write a view that will return some common data and then list the service offerings on one line. For example: Standard Id | Description | SO #1 | SO #2 | SO #3 | ... | SO #21 | SO Count 1 | One | A | B | C | ... | G | 21 2 | Two | A | | | ... | | 1 3 | Three | B | D | E | ... | | 3 I have no idea how to write this. The number of SO columns is set to a specific number (21 in this case), so we cannot exceed past that. Any ideas on how to approach this? A place I started is below. It just returned multiple rows for each Service Offering, when they need to be on one row. SELECT * FROM SERVICE_OFFERINGS WHERE STANDARD_KEY IN (SELECT STANDARD_KEY FROM STANDARDS)

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• MS Excel automation without macros in the generated reports. Any thoughts?

  - by ezeki77

  Hello! I know that the web is full of questions like this one, but I still haven't been able to apply the answers I can find to my situation. I realize there is VBA, but I always disliked having the program/macro living inside the Excel file, with the resulting bloat, security warnings, etc. I'm thinking along the lines of a VBScript that works on a set of Excel files while leaving them macro-free. Now, I've been able to "paint the first column blue" for all files in a directory following this approach, but I need to do more complex operations (charts, pivot tables, etc.), which would be much harder (impossible?) with VBScript than with VBA. For this specific example knowing how to remove all macros from all files after processing would be enough, but all suggestions are welcome. Any good references? Any advice on how to best approach external batch processing of Excel files will be appreciated. Thanks! PS: I eagerly tried Mark Hammond's great PyWin32 package, but the lack of documentation and interpreter feedback discouraged me.

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• Using Memcached in Python/Django - questions.

  - by Thomas

  I am starting use Memcached to make my website faster. For constant data in my database I use this: from django.core.cache import cache cache_key = 'regions' regions = cache.get(cache_key) if result is None: """Not Found in Cache""" regions = Regions.objects.all() cache.set(cache_key, regions, 2592000) #(2592000sekund = 30 dni) return regions For seldom changed data I use signals: from django.core.cache import cache from django.db.models import signals def nuke_social_network_cache(self, instance, **kwargs): cache_key = 'networks_for_%s' % (self.instance.user_id,) cache.delete(cache_key) signals.post_save.connect(nuke_social_network_cache, sender=SocialNetworkProfile) signals.post_delete.connect(nuke_social_network_cache, sender=SocialNetworkProfile) Is it correct way? I installed django-memcached-0.1.2, which show me: Memcached Server Stats Server Keys Hits Gets Hit_Rate Traffic_In Traffic_Out Usage Uptime 127.0.0.1 15 220 276 79% 83.1 KB 364.1 KB 18.4 KB 22:21:25 Can sombody explain what columns means? And last question. I have templates where I am getting much records from a few table (relationships). So in my view I get records from one table and in templates show it and related info from others. Generating page last a few seconds for very small table (<100records). Is it some easy way to cache queries from templates? Have I to do some big structure in my view (with all related tables), cache it and send to template?

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• C# sqlite syntax in ASP.NET?

  - by acidzombie24

  -edit- This is no longer relevant and the question doesnt make sense to me anymore. I think i wanted to know how to create tables or know if the syntax is the same from winform to ASP.NET I am very use to sqlite http://sqlite.phxsoftware.com/ and would like to create a DB in a similar style. How do i do this? it doesnt need to be the same, just similar enough for me to enjoy. An example of the syntax. connection = new SQLiteConnection("Data Source=" + sz +";Version=3"); command = new SQLiteCommand(connection); connection.Open(); command.CommandText = "CREATE TABLE if not exists miscInfo(key TEXT, " + "value TEXT, UNIQUE (key));"; command.ExecuteNonQuery(); The @name is a symbol and command.Parameters.Add("@userDesc", DbType.String).Value = d.userDesc; replaces the symbol with escaped values/texts/blob command.CommandText = "INSERT INTO discData(rootfolderID, time, volumeName, discLabel, " + "userTitle, userDesc) "+ "VALUES(@rootfolderID, @time, @volumeName, @discLabel, " + "@userTitle, @userDesc); " + "SELECT last_insert_rowid() AS RecordID;"; command.Parameters.Add("@rootfolderID", DbType.Int64).Value = d.rootfolderID; command.Parameters.Add("@time", DbType.Int64).Value = d.time; command.Parameters.Add("@volumeName", DbType.String).Value = d.volumeName; command.Parameters.Add("@discLabel", DbType.String).Value = d.discLabel; command.Parameters.Add("@userTitle", DbType.String).Value = d.userTitle; command.Parameters.Add("@userDesc", DbType.String).Value = d.userDesc; d.discID = (long)command.ExecuteScalar();

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• SQLAlchemy Mapping problem

  - by asdvalkn

  Dear Everyone, I am trying to sqlalchemy to correctly map my data. Note that a unified group is basically a group of groups. (One unifiedGroup maps to many groups but each group can only map to one ug). So basically this is the definition of my unifiedGroups: CREATE TABLE `unifiedGroups` ( `ugID` INT AUTO_INCREMENT, `gID` INT NOT NULL, PRIMARY KEY(`ugID`, `gID`), KEY( `gID`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 ; Note that each row is a ugID, gID tuple. ( I do not know before hand how many gID is per ugID so this is probably the most sensible and simplest method). Definition for my UnifiedGroup class class UnifiedGroup(object): """UnifiedProduct behaves very much like a group """ def __init__(self, ugID): self.ugID=ugID #Added by mapping self.groups=False def __str__(self): return '<%s:%s>' % (self.ugID, ','.join( [g for g in self.groups])) These are my mapping tables: tb_groupsInfo = Table( 'groupsInfo', metadata, Column('gID', Integer, primary_key=True), Column('gName', String(128)), ) tb_unifiedGroups = Table( 'unifiedGroups', metadata, Column('ugID', Integer, primary_key=True), Column('gID', Integer, ForeignKey('groupsInfo.gID')), ) My mapper maps in the following manner: mapper( UnifiedGroup, tb_unifiedGroups, properties={ 'groups': relation( Group, backref='unifiedGroup') }) However, when I tried to do groupInstance.unifiedGroup, I am getting an empty list [], while groupInstance.unifiedGroup.groups returns me an error: AttributeError: 'InstrumentedList' object has no attribute 'groups' Traceback (most recent call last): File "Mapping.py", line 119, in <module> print p.group.unifiedGroup.groups AttributeError: 'InstrumentedList' object has no attribute 'groups' What is wrong?

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• How Optimize sql query make it faster

  - by user502083

  Hello every one : I have a very simple small database, 2 of tables are: Node (Node_ID, Node_name, Node_Date) : Node_ID is primary key Citation (Origin_Id, Target_Id) : PRIMARY KEY (Origin_Id, Target_Id) each is FK in Node Now I write a query that first find all citations that their Origin_Id has a specific date and then I want to know what are the target dates of these records. I'm using sqlite in python the Node table has 3000 record and Citation has 9000 records, and my query is like this in a function: def cited_years_list(self, date): c=self.cur try: c.execute("""select n.Node_Date,count(*) from Node n INNER JOIN (select c.Origin_Id AS Origin_Id, c.Target_Id AS Target_Id, n.Node_Date AS Date from CITATION c INNER JOIN NODE n ON c.Origin_Id=n.Node_Id where CAST(n.Node_Date as INT)={0}) VW ON VW.Target_Id=n.Node_Id GROUP BY n.Node_Date;""".format(date)) cited_years=c.fetchall() self.conn.commit() print('Cited Years are : \n ',str(cited_years)) except Exception as e: print('Cited Years retrival failed ',e) return cited_years Then I call this function for some specific years, But it's crazy slowwwwwwwww :( (around 1 min for a specific year) Although my query works fine, it is slow. would you please give me a suggestion to make it faster? I'd appreciate any idea about optimizing this query :) I also should mention that I have indices on Origin_Id and Target_Id, so the inner join should be pretty fast, but it's not!!!

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• Selecting random top 3 listings per shop for a range of active advertising shops

  - by GraGra33

  I’m trying to display a list of shops each with 3 random items from their shop, if they have 3 or more listings, that are actively advertising. I have 3 tables: one for the shops – “Shops”, one for the listings – “Listings” and one that tracks active advertisers – “AdShops”. Using the below statement, the listings returned are random however I’m not getting exactly 3 listings (rows) returned per shop. SELECT AdShops.ID, Shops.url, Shops.image_url, Shops.user_name AS shop_name, Shops.title, L.listing_id AS listing_id, L.title AS listing_title, L.price as price, L.image_url AS listing_image_url, L.url AS listing_url FROM AdShops INNER JOIN Shops ON AdShops.user_id = Shops.user_id INNER JOIN Listings AS L ON Shops.user_id = L.user_id WHERE (Shops.is_vacation = 0 AND Shops.listing_count > 2 AND L.listing_id IN (SELECT TOP 3 L2.listing_id FROM Listings AS L2 WHERE L2.listing_id IN (SELECT TOP 100 PERCENT L3.listing_id FROM Listings AS L3 WHERE (L3.user_id = L.user_id) ) ORDER BY NEWID() ) ) ORDER BY Shops.shop_name I’m stumped. Anyone have any ideas on how to fix it? The ideal solution would be one record per store with the 3 listings (and associated data) were in columns and not rows – is this possible?

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