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  • How can i design a DB where the user can define the fields and types of a detail table in a M-D rela

    - by Simon
    My application has one table called 'events' and each event has approx 30 standard fields, but also user defined fields that could be any name or type, in an 'eventdata' table. Users can define these event data tables, by specifying x number of fields (either text/double/datetime/boolean) and the names of these fields. This 'eventdata' (table) can be different for each 'event'. My current approach is to create a lookup table for the definitions. So if i need to query all 'event' and 'eventdata' per record, i do so in a M-D relaitionship using two queries (i.e. select * from events, then for each record in 'events', select * from 'some table'). Is there a better approach to doing this? I have implemented this so far, but most of my queries require two distinct calls to the DB - i cannot simply join my master 'events' table with different 'eventdata' tables for each record in in 'events'. I guess my main question is: can i join my master table with different detail tables for each record? E.g. SELECT E.*, E.Tablename FROM events E LEFT JOIN 'E.tablename' T ON E._ID = T.ID If not, is there a better way to design my database considering i have no idea on how many user defined fields there may be and what type they will be.

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  • Handling large datasets with PHP/Drupal

    - by jo
    Hi all, I have a report page that deals with ~700k records from a database table. I can display this on a webpage using paging to break up the results. However, my export to PDF/CSV functions rely on processing the entire data set at once and I'm hitting my 256MB memory limit at around 250k rows. I don't feel comfortable increasing the memory limit and I haven't got the ability to use MySQL's save into outfile to just serve a pre-generated CSV. However, I can't really see a way of serving up large data sets with Drupal using something like: $form = array(); $table_headers = array(); $table_rows = array(); $data = db_query("a query to get the whole dataset"); while ($row = db_fetch_object($data)) { $table_rows[] = $row->some attribute; } $form['report'] = array('#value' => theme('table', $table_headers, $table_rows); return $form; Is there a way of getting around what is essentially appending to a giant array of arrays? At the moment I don't see how I can offer any meaningful report pages with Drupal due to this. Thanks

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  • Setting up a NAS with Citrix XenServer

    - by JasonBrown
    Just a quick query on anyone whos worked with XenServer, I want to setup a NAS at home but with virtualization (I've looked into VMWare Server and KVM, I quite like KVM!) but I was told about XenServer 5.5. I have comomodity hardware (ASUS board, dual core 2.66Ghz CPU with 8Gb RAM), I need to setup a fileserver to house about 2-3Tb worth of data (big chunky video - not porn!). Need to run Linux (preferably CentOS) but also run Windows virtualised for testing. I was thinking of going the XenServer route, however I want to be able to offer a VM access to the 2-3Tb of HDDs (5 HDD drives) directly so it can do its thing (maybe using FreeNAS). Would this be possible with XenServer? Or will I have to do more work - and another box - to offer this? My goals are to use FreeNAS (ZFS!) for the filesserver, CentOS for SVN and aother bits we need to use (LAMP Stack), Windows for our win32 testing all on one box. I see this iSCSI target bits and get scared.

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  • How to convert object to string list?

    - by user1381501
    I want to get two values by using linq select query and try to convert object to string list. I am trying to convert list to list. The code as below. I got the error when I convert object to string list : return returnvalue = (List)userlist; public List<string> GetUserList(string username) { List<User> UserList = new List<User>(); List<string> returnvalue=new List<string>(); try { string returnstring = string.Empty; DataTable dt = null; dt = Library.Helper.FindUser(username, 200); foreach (DataRow dr in dt.Rows) { User user = new User(); spuser.id = dr["ID"].ToString(); spuser.name = dr["Name"].ToString(); UserList.Adduser } } catch (Exception ex) { } List<SharePointMentoinUser> userlist = UserList.Select(a => new User { name = (string)a.name, id = (string)a.id }).ToList(); **return returnvalue = (List<string>)userlist;** }

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  • mysql - multiple where and search

    - by Shamil
    I'm trying to write a SQL query that satisfies multiple criteria. Of these, most are connected via a column, so joins are possible, however, some queries are such that I'd have to search additional tables for the information. What would be the least expensive and best way to do this? Let's say that we have a few tables. One table contains information such as sales information for a server: the salesperson, client id, service lease term, timestamps etc. It is possible that a client has multiple sales but with a different "service". I'd need to pick up all of the different ones. Another table has the quotes for the services, I'd need to pick some information out about this, whilst another, which could be joined to this one has some more information. Those tables are linked by a common client ID, so joins are possible, but I'd also need to search the first table for multiple instances of the client ID. Of course, I'd want to restrict the search to certain timestamps, which I can easily do as the timestamps are stored in MySQL format.

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  • mysql to codeigniter active record help

    - by JoeM05
    Active record is a neet concept but sometimes I find it difficult to get more complicated queries to work. I find this is at least one place the CI docs are lacking. Anyway, This is the sql I wrote. It returns the expected results of quests not yet completed by the user that are unlocked and within the users level requirements: SELECT writing_quests . * FROM `writing_quests` LEFT OUTER JOIN members_quests_completed ON members_quests_completed.quest_id = writing_quests.id LEFT OUTER JOIN members ON members.id = $user_id WHERE writing_quests.unlocked =1 AND writing_quests.level_required <= $userlevel AND members_quests_completed.user_id IS NULL This is the codeigniter active record query, it returns all quests that are unlocked and within the users level requirement: $this->db->select('writing_quests.*'); $this->db->from('writing_quests'); $this->db->join('members_quests_completed', 'members_quests_completed.quest_id = writing_quests.id', 'left outer'); $this->db->join('members', "members.id = $user_id", 'left outer'); $this->db->where('writing_quests.unlock', 1); $this->db->where('writing_quests.level_required <=', $userlevel); $this->db->where('members_quests_completed.user_id is null', null, true); I'm guessing there is something wrong with the way I am asking for Nulls. To be thorough, I figured I'd include everything.

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  • Many tables for many users?

    - by Seagull
    I am new to web programming, so excuse the ignorance... ;-) I have a web application that in many ways can be considered to be a multi-tenant environment. By this I mean that each user of the application gets their own 'custom' environment, with absolutely no interaction between those users. So far I have built the web application as a 'single user' environment. In other words, I haven't actually done anything to support multi-users, but only worked on the functionality I want from the app. Here is my problem... What's the best way to build a multi-user environment: All users point to the same 'core' backend. In other words, I build the logic to separate users via appropriate SQL queries (eg. select * from table where user='123' and attribute='456'). Each user points to a unique tablespace, which is built separately as they join the system. In this case I would simply generate ALL the relevant SQL tables per user, with some sort of suffix for the user. (eg. now a query would look like 'select * from table_ where attribute ='456'). In short, it's a difference between "select * from table where USER=" and "select * from table_USER".

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  • Facebook / Offline Permission - Trying to perform an action on a set of offline users.

    - by blueigloo
    Hi there, We're building an app which in part of its functionality tries to capture the number of likes associated to a particular video owned by a user. Users of the app are asked for extended off-line access and we capture the key for each user: The format is like this: 2.hg2QQuYeftuHx1R84J1oGg__.XXXX.1272394800-nnnnnn Each user has their offline / infinite key stored in a table in a DB. The object_id which we're interested in is also stored in the DB. At a later stage (offline) we try to run a batch job which reads the number of likes for each user's video. (See attached code) For some reason however, after the first iteration of the loop - which yields the likes correctly, we get a failure with the oh so familiar message: "Session key is invalid or no longer valid" Any insight would be most appreciated. Thanks, B List<DVideo> videoList = db.SelectVideos(); foreach (DVideo video in videoList) { long userId = 0; ConnectSession fbSession = new ConnectSession(APPLICATION_KEY, SECRET_KEY); //session key is attached to the video object for now. fbSession.SessionKey = video.UserSessionKey; fbSession.SessionExpires = false; string fbuid =video.FBUID; long.TryParse(fbuid, out userId); if (userId > 0) { fbSession.UserId = userId; fbSession.Login(); Api fbApi = new Facebook.Rest.Api(fbSession); string xmlQueryResult = fbApi.Fql.Query("SELECT user_id FROM like WHERE object_id = " + video.FBVID); XmlDocument xmlDoc = new XmlDocument(); xmlDoc.Load(new StringReader(xmlQueryResult)); int likesCount = xmlDoc.GetElementsByTagName("user_id").Count; //Write entry in VideoWallLikes if (likesCount > 0) { db.CountWallLikes(video.ID, likesCount); } fbSession.Logout(); } fbSession = null; }

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  • Database solution for 200million writes/day, monthly summarization queries

    - by sb
    Hello. I'm looking for help deciding on which database system to use. (I've been googling and reading for the past few hours; it now seems worthwhile to ask for help from someone with firsthand knowledge.) I need to log around 200 million rows (or more) per 8 hour workday to a database, then perform weekly/monthly/yearly summary queries on that data. The summary queries would be for collecting data for things like billing statements, eg. "How many transactions of type A did each user run this month?" (could be more complex, but that's the general idea). I can spread the database amongst several machines, as necessary, but I don't think I can take old data offline. I'll definitely need to be able to query a month's worth of data, maybe a year. These queries would be for my own use, and wouldn't need to be generated in real-time for an end-user (they could run overnight, if needed). Does anyone have any suggestions as to which databases would be a good fit? P.S. Cassandra looks like it would have no problem handling the writes, but what about the huge monthly table scans? Is anyone familiar with Cassandra/Hadoop MapReduce performance?

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  • Can a second stored procedure doing the same thing finish before first one?

    - by evanmortland
    Hello, I have an audit record table that I am writing to. I am connecting to MyDb, which has a stored procedure called 'CreateAudit', which is a passthrough stored procedure to another database on the same machine called 'CreatedAudit' as well. I call the CreateAudit stored procedure from my application, using subsonic as the DAL. The first time I call it, I call it with the following (pseudocode): Result = CreateAudit(recordId, "Opened") Right after that, I call: Result2 = CreateAudit(recordId, "Closed") In my second stored procedure it is supposed to mark the record that was created by the CreateAudit(recordId, "Opened") with a status of closed. It works great if I run them independently of one another, but when they run in sequence in the application, the record is not marked as "Closed". When I run SQL profiler I see that both queries ran, and if I copy the queries out and run them from query analyzer the record gets marked as closed 100% of the time! When I run it from the application, about once every 20 times or so, the record is successfully marked closed - the other 19 times nothing happens, but I do not get an error! Is it possible for the .NET app to skip over the ouput from the first stored procedure and start executing the second stored procedure before the record in the first is created? When I add a "WAITFOR DELAY '00:00:00:003'" to the top of my stored procedure, the record is also closed 100% of the time. My head is spinning, any ideas why this is happening! Thanks for any responses, very interested in hearing how this can happen.

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  • Detecting well behaved / well known bots

    - by Simon_Weaver
    I found this question very interesting : Programmatic Bot Detection I have a very similar question, but I'm not bothered about 'badly behaved bots'. I am tracking (in addition to google analytics) the following per visit : Entry URL Referer UserAgent Adwords (by means of query string) Whether or not the user made a purchase etc. The problem is that to calculate any kind of conversion rate I'm ending up with lots of 'bot' visits that are greatly skewing my results. I'd like to ignore as many as possible bot visits, but I want a solution that I don't need to monitor too closely, and that won't in itself be a performance hog and preferably still work if someone has javascript disabled. Are there good published lists of the top 100 bots or so? I did find a list at http://www.user-agents.org/ but that appears to contain hundreds if not thousands of bots. I don't want to check every referer against thousands of links. Here is the current googlebot UserAgent. How often does it change? Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)

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  • How to structure code with 2 methods, one after another, which throw the same two exceptions?

    - by dotnetdev
    Hi, I have two methods, one called straight after another, which both throw the exact same 2 exceptions (IF an erroneous condition occurs, not stating that I'm getting exceptions). For this, should I write seperate try and catch blocks with the one statement in each try block and catch both exceptions (Both of which I can handle as I checked MSDN class library reference and there is something I can do, eg, re-open SqlConnection or run a query and not a stored proc which does not exist). So code like this: try { obj.Open(); } catch (SqlException) { // Take action here. } catch (InvalidOperationException) { // Take action here. } And likewise for the other method I call straight after. This seems like a very messy way of coding. The other way is to code with the exception variable (that is ommited as I am using AOP to log the exception details, using a class-level attribute). Doing this, this could aid me in finding out which method caused an exception and then taking action accordingly. Is this the best approach or is there another best practise altogether? I also assume that, as only these two methods are thrown, I do not need to catch Exception as that would be for an exception I cannot handle (causes way out of my control). Thanks

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  • PHP & MySQL username validation and storage problem.

    - by php
    For some reason when a user enters a brand new username the error message <p>Username unavailable</p> is displayed and the name is not stored. I was wondering if some can help find the flaw in my code so I can fix this error? Thanks Here is the PHP code. if($_POST['username'] && trim($_POST['username'])!=='') { $u = "SELECT * FROM users WHERE username = '$username' AND user_id <> '$user_id'"; $r = mysqli_query ($mysqli, $u) or trigger_error("Query: $u\n<br />MySQL Error: " . mysqli_error($mysqli)); if (mysqli_num_rows($r) == TRUE) { echo '<p>Username unavailable</p>'; $_POST['username'] = NULL; } else if(isset($_POST['username']) && mysqli_num_rows($r) == 0 && strlen($_POST['username']) <= 255) { $username = mysqli_real_escape_string($mysqli, $_POST['username']); } else if($_POST['username'] && strlen($_POST['username']) >= 256) { echo '<p>Username can not exceed 255 characters</p>'; } }

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  • No result when Rally.data.WsapiDataStore lacks permissions

    - by user1195996
    I'm calling Ext.create('Rally.data.WsapiDataStore', params), and looking for results with the load event. I'm requesting a number of objects across programs that the user may or may not have read permission for. This works fine for queries where the user has permissions. But in the case where the user does not have permission and presumably gets zero results back, the load event does not seem to fire at all. I would expect it to fire with the unsuccessful flag or else to return with empty results. Since I don't know that the request has failed, my program waits and waits. How can I tell if a this request fails to return because of security? BTW, looking at the network stats, I believe all my requests get a "200 OK" status back. Here is the method I use to create the various data stores: _createDataStore: function(params) { this.openRequests++; var createParams = { model: params.type, autoLoad: true, // So I can later determine which query type it is, and which program requestType: params.requestType == undefined ? params.type : params.requestType, program: this.program, listeners: { load: this._onDataLoaded, scope: this }, filters: params.filters, pageSize: params.pageSize, fetch: params.fetch, context: { project: this.project, projectScopeUp: false, projectScopeDown: true }, pageSize: 1 // We only need the count }; console.log('_createDataStore', this.program, createParams.requestType); Ext.create('Rally.data.WsapiDataStore', createParams); }, And here is the _onDataLoaded method: _onDataLoaded: function(store, data, successB) { console.log('_onDataLoaded', this.program, successB); ... I only see this function called for those queries for which the account has permissions.

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  • Solr return whether member is in multivalued field

    - by ??iu
    Is there any way to return in the fields list whether a value exists as one of the values of a multivalued field? E.g., if your schema is <schema> ... <field name="user_name" type="text" indexed="true" stored="true" required="true" /> <field name="follower" type="integer" indexed="true" stored="true" multiValued="true" /> ... </schema> A sample document might look like: <doc> <field name="user_name">tester blah</field> <field name="follower">1</field> <field name="follower">62</field> <field name="follower">63</field> <field name="follower">64</field> </doc> I would like to be able to query for, say, "tester" and follower:62 and have it match "tester blah" and have some indication of whether 62 is a follower or not in the results.

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  • Add to exisiting db values, rather than overwrite - PDO

    - by sam
    Im trying to add to existing decimal value in table, for which im using the sql below: UPDATE Funds SET Funds = Funds + :funds WHERE id = :id Im using a pdo class to handle my db calls, with the method below being used to update the db, but i couldnt figure out how to amend it to output the above query, any ideas ? public function add_to_values($table, $info, $where, $bind="") { $fields = $this->filter($table, $info); $fieldSize = sizeof($fields); $sql = "UPDATE " . $table . " SET "; for($f = 0; $f < $fieldSize; ++$f) { if($f > 0) $sql .= ", "; $sql .= $fields[$f] . " = :update_" . $fields[$f]; } $sql .= " WHERE " . $where . ";"; $bind = $this->cleanup($bind); foreach($fields as $field) $bind[":update_$field"] = $info[$field]; return $this->run($sql, $bind); }

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  • MySQL Delete Records Older Than X Minutes?

    - by sajanNOPPIX
    I've searched quite a bit and found a few solutions that didn't end up working for me and can't understand why. I have a table with a timestamp column. The MySQL type for this column is 'datetime'. I insert into this table the following from PHP. date('Y-m-d H:i:s') This enters, what looks like the correct value for the MySQL date time. 2012-06-28 15:31:46 I want to use this column to delete rows that are older than say 10 minutes. I'm running the following query, but it's not working. It affects 0 rows. DELETE FROM adminLoginLog WHERE timestamp < (NOW() - INTERVAL 10 MINUTE); Can anyone shed some light as to what I'm doing wrong and why it's not working properly? Thanks. Update: It looks like my first issue is that I'm using DATETIME when I should be using the TIMESTAMP data type. I'm updating my code to do that now. Thanks.

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  • Logic in the db for maintaining a points system relationship?

    - by MarcusBooster
    I'm making a little web based game and need to determine where to put logic that checks the integrity of some underlying data in the sql database. Each user keeps track of points assigned to him, and points are awarded by various tasks. I keep a record of each task transaction to make sure they're not repeated, and to keep track of the value of the task at the time of completion, since an individual award level my fluctuate over time. My schema looks like this so far: create table player ( player_ID serial primary key, player_Points int not null default 0 ); create table task ( task_ID serial primary key, task_PointsAwarded int not null ); create table task_list ( player_ID int references player(player_ID), task_ID int references task(task_ID), when_completed timestamp default current_timestamp, point_value int not null, --not fk because task value may change later constraint pk_player_task_id primary key (player_ID, task_ID) ); So, the player.player_Points should be the total of all his cumulative task points in the task_list. Now where do I put the logic to enforce this? Should I do away with player.player_Points altogether and do queries every time I want to know the total score? Which seems wasteful since I'll be doing that query a lot over the course of a game. Or, put a trigger in the task_list that automatically updates the player.player_Points? Is that too much logic to have in the database and should just maintain this relationship in the application? Thanks.

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  • Very fast document similarity

    - by peyton
    Hello, I am trying to determine document similarity between a single document and each of a large number of documents (n ~= 1 million) as quickly as possible. More specifically, the documents I'm comparing are e-mails; they are grouped (i.e., there are folders or tags) and I'd like to determine which group is most appropriate for a new e-mail. Fast performance is critical. My a priori assumption is that the cosine similarity between term vectors is appropriate for this application; please comment on whether this is a good measure to use or not! I have already taken into account the following possibilities for speeding up performance: Pre-normalize all the term vectors Calculate a term vector for each group (n ~= 10,000) rather than each e-mail (n ~= 1,000,000); this would probably be acceptable for my application, but if you can think of a reason not to do it, let me know! I have a few questions: If a new e-mail has a new term never before seen in any of the previous e-mails, does that mean I need to re-compute all of my term vectors? This seems expensive. Is there some clever way to only consider vectors which are likely to be close to the query document? Is there some way to be more frugal about the amount of memory I'm using for all these vectors? Thanks!

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  • How to initialize list with parent child relation

    - by user2917702
    Let's say I have the following classes. public class Parent { public string name; IList<Children> children; } public class Child { public string parentName; public int age; } As it is understandable, each parent can have multiple children, and we can have multiple parents. What is the best way to initialize these classes? Is it better to get all of the parents, and all of the children from database then use LINQ? IList<Parent> parents = GetParents()//assume this gets parents from db IList<Child> children = GetChildren() //assume this gets children from db foreach(Parent parent in parents) { parent.children = children.Where(x=>x.parentName==parent.name).ToList(); } or get all of the parents and iterate through each parent to query database by parentName to get children information? Due to requirement that I have, I cannot use datatable or dataset; I can only use datareader. IList<Parent> parents = GetParents()//assume this gets parents from db foreach(Parent parent in parents) { parent.children = GetChildrenByParentName();//assume this gets parents from db by parentName } Thank you

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  • Further filter SQL results

    - by eric
    I've got a query that returns a proper result set, using SQL 2005. It is as follows: select case when convert(varchar(4),datepart(yyyy,bug.datecreated),101)+ ' Q' +convert(varchar(2),datepart(qq,bug.datecreated),101) = '1969 Q4' then '2009 Q2' else convert(varchar(4),datepart(yyyy,bug.datecreated),101)+ ' Q' +convert(varchar(2),datepart(qq,bug.datecreated),101) end as [Quarter], bugtypes.bugtypename, count(bug.bugid) as [Total] from bug left outer join bugtypes on bug.crntbugtypeid = bugtypes.bugtypeid and bug.projectid = bugtypes.projectid where (bug.projectid = 44 and bug.currentowner in (-1000000031,-1000000045) and bug.crntplatformid in (42,37,25,14)) or (bug.projectid = 44 and bug.currentowner in (select memberid from groupmembers where projectid = 44 and groupid in (87,88)) and bug.crntplatformid in (42,37,25,14)) group by case when convert(varchar(4),datepart(yyyy,bug.datecreated),101)+ ' Q' +convert(varchar(2),datepart(qq,bug.datecreated),101) = '1969 Q4' then '2009 Q2' else convert(varchar(4),datepart(yyyy,bug.datecreated),101)+ ' Q' +convert(varchar(2),datepart(qq,bug.datecreated),101) end, bugtypes.bugtypename order by 1,3 desc It produces a nicely grouped list of years and quarters, an associated descriptor, and a count of incidents in descending count order. What I'd like to do is further filter this so it shows only the 10 most submitted incidents per quarter. What I'm struggling with is how to take this result set and achieve that.

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  • C++ CRTP question

    - by aaa
    following piece of code does not compile, the problem is in T::rank not be inaccessible (I think) or uninitialized in parent template. Can you tell me exactly what the problem is? is passing rank explicitly the only way? or is there a way to query tensor class directly? Thank you #include <boost/utility/enable_if.hpp> template<class T, // size_t N, class enable = void> struct tensor_operator; // template<class T, size_t N> template<class T> struct tensor_operator<T, typename boost::enable_if_c< T::rank == 4>::type > { tensor_operator(T &tensor) : tensor_(tensor) {} T& operator()(int i,int j,int k,int l) { return tensor_.layout.element_at(i, j, k, l); } T &tensor_; }; template<size_t N, typename T = double> // struct tensor : tensor_operator<tensor<N,T>, N> { struct tensor : tensor_operator<tensor<N,T> > { static const size_t rank = N; }; I know the workaround, however am interested in mechanics of template instantiation for self-education

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  • How to get a category listing from Magento?

    - by alex
    I want to create a page in Magento that shows a visual representation of the categories.. example CATEGORY product 1 product 2 ANOTHER CATEGORY product 3 My problem is, their database is organised very differently to what I've seen in the past. They have tables dedicated to data types like varchar, int, etc. I assume this is for performance or similiar. I haven't found a way to use MySQL to query the database and get a list of categories. I'd then like to match these categories to products, to get a listing of products for each category. Unfortunately Magento seems to make this very difficult. Also I have not found a method that will work from within a page block.. I have created showcase.phtml and put it in the XML layout and it displays and runs it's PHP code. I was hoping for something easy like looping through $this-getAllCategories(); and then a nested loop inside with something like $category-getChildProducts(); Can anyone help me? Thank you!

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  • Java doest run prepare statements with parameter

    - by Zaiman Noris
    If using PreparedStatement to query my table. Unfortunately, I have not been able to do so. My code is as simple as this :- PreparedStatement preparedStatement = connection.prepareStatement( "Select favoritefood from favoritefoods where catname = ?"); preparedStatement.setString(1, "Cappuccino"); ResultSet resultSet = preparedStatement.executeQuery(); Error thrown is java.sql.SQLException: ORA-00911: invalid character. As if it never run through the parameter given. Thanks for your time. I've spend a day to debug this yet still unsuccessful. As mention by Piyush, if I omit the semicolon at the end of statement, new error is thrown. java.sql.SQLException: ORA-00942: table or view does not exist. But I can assure you this table is indeed exist. UPDATE shoot. i edited the wrong sql. now it is successful. thx for your time.

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  • How do I do a table join on two fields in my second table?

    - by Cannonade
    I have two tables: Messages - Amongst other things, has a to_id and a from_id field. People - Has a corresponding person_id I am trying to figure out how to do the following in a single linq query: Give me all messages that have been sent to and from person x (idself). I had a couple of cracks at this. Not quite right MsgPeople = (from p in db.people join m in db.messages on p.person_id equals m.from_id where (m.from_id == idself || m.to_id == idself) orderby p.name descending select p).Distinct(); This almost works, except I think it misses one case: "people who have never received a message, just sent one to me" How this works in my head So what I really need is something like: join m in db.messages on (p.people_id equals m.from_id or p.people_id equals m.to_id) Gets me a subset of the people I am after It seems you can't do that. I have tried a few other options, like doing two joins: MsgPeople = (from p in db.people join m in AllMessages on p.person_id equals m.from_id join m2 in AllMessages on p.person_id equals m2.to_id where (m2.from_id == idself || m.to_id == idself) orderby p.name descending select p).Distinct(); but this gives me a subset of the results I need, I guess something to do with the order the joins are resolved. My understanding of LINQ (and perhaps even database theory) is embarrassingly superficial and I look forward to having some light shed on my problem.

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