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  • Does a static object within a function introduce a potential race condition?

    - by Jeremy Friesner
    I'm curious about the following code: class MyClass { public: MyClass() : _myArray(new int[1024]) {} ~MyClass() {delete [] _myArray;} private: int * _myArray; }; // This function may be called by different threads in an unsynchronized manner void MyFunction() { static const MyClass _myClassObject; [...] } Is there a possible race condition in the above code? Specifically, is the compiler likely to generate code equivalent to the following, "behind the scenes"? void MyFunction() { static bool _myClassObjectInitialized = false; if (_myClassObjectInitialized == false) { _myClassObjectInitialized = true; _myClassObject.MyClass(); // call constructor to set up object } [...] } ... in which case, if two threads were to call MyFunction() nearly-simultaneously, then _myArray might get allocated twice, causing a memory leak? Or is this handled correctly somehow?

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  • When saving a model with has_one or has_many associations, which side of the association is saved fi

    - by SeeBees
    I have three simplified models: class Team < ActiveRecord::Base has_many :players has_one :coach end class Player < ActiveRecord::Base belongs_to :team validates_presence_of :team_id end class Coach < ActiveRecord::Base belongs_to :team validates_presence_of :team_id end I use the following code to test these models: t = Team.new team.coach = Coach.new team.save! team.save! returns true. But in another test: t = Team.new team.players << Player.new team.save! team.save! gives the following error: > ActiveRecord::RecordInvalid: > Validation failed: Players is invalid > from > /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/validations.rb:1090:in > `save_without_dirty!' from > /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/dirty.rb:87:in `save_without_transactions!' from > /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:200:in > `save!' from > /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/connection_adapters/abstract/database_statements.rb:136:in > `transaction' from > /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:182:in > `transaction' from > /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:200:in > `save!' from > /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:208:in > `rollback_active_record_state!' from > /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:200:in > `save!' from (irb):14 I figured out that when team.save! is called, it first calls player.save!. player needs to validate the presence of the id of the associated team. But at the time player.save! is called, team hasn't been saved yet, and therefore, team_id doesn't yet exist for player. This fails the player's validation, so the error occurs. But on the other hand, team is saved before coach.save!, otherwise the first example will get the same error as the second one. So I've concluded that when a has_many bs, a.save! will save bs prior to a. When a has_one b, a.save! will save a prior to b. If I am right, why is this the case? It doesn't seem logical to me. Why do has_one and has_many association have different order in saving? Any ideas? And is there any way I can change the order? Say I want to have the same saving order for both has_one and has_many. Thanks.

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  • Django left join m2m field.

    - by duder
    Here's my Model: class User(models.Model): pass class Item(models.Model): pass class ItemVote(models.Model): user = models.ForeignKey(User) item = models.ForeignKey(Item) vote = models.BooleanField() I want to retrieve a list of Items, and I want to know if the current user has voted for each Item. How do I alter my query object so that it will generate sql similar to: SELECT ... FROM items LEFT OUTER JOIN item_votes ON (item_votes.user_id = ? AND item_votes.item_id = items.id)

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  • PHP - preg_replace with multiple matches

    - by Neil
    Let's say I have a string like: $text = "<object>item_id1a2b3</object>xxx<object>item_id4c5d6</object>" I want to convert it to: %ITEM:1a2b3xxx%ITEM:4c5d6 Here's what I've got: $text = preg_replace("/<object.*item_id([a-zA-Z0-9]+).*<\/object/","%ITEM:$1",$text); This isn't quite right, as the search is greedy. Thoughts? Thanks!

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  • How to page multiple data sets in ASP.NET MVC

    - by REA_ANDREW
    On a single view I will have three sets of paged data. Which means for each model I will have The Objects The Page Index The Page Size My initial thought was for example: public class PagedModel<T> where T:class { public IList<T> Objects { get; set; } public int ModelPageIndex { get; set; } public int ModelPageSize { get; set; } } Then having a model which is to be supplied to the action as for example: public class TypesViewModel { public PagedModel<ObjectA> Types1 { get; set; } public PagedModel<ObjectB> Typed2 { get; set; } public PagedModel<ObjectC> Types3 { get; set; } } So if I then for example have the Index view inherit from the type: System.Web.Mvc.ViewPage<uk.co.andrewrea.forum.Web.Models.TypesViewModel> Now my initial aciton method for the index is simply: public ActionResult Index() { var forDisplayPurposes = new TypesViewModel(); return View(forDisplayPurposes); } If I then want to page, it is here where I am struggling to decide which action to take. Lets say that I select the next page of the Types2 PageModel. What should the action look like for this in order to return the new view showing the second page of the Types2 PageModel I was thinking possibly to duplicate the action but use it with POST [AcceptVerbs(HttpVerbs.Post)] public ActionResult Index(TypesViewModel model) { return View(model); } Is this a good way to approach it. I understand there is always Session, but I was just wondering how such a thing is achieved currently out there. If any best methods have been mutually accepted and things. So simply, one page with multiple paged models. How to persist the data for each using a wrapper model. Which way should you pass in the model and which way should you page the data, i.e. Form Post Lastly, I have seen the routes take this into account i.e. {controller}/{action}/{id}/{pageindex}/{pagesize} but this only accounts for one model and I do not really wwant to repeat the pagesize and pageindex values for the number of models I have inside the wrapper model. Thanks for your time!! Andrew

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  • How do I get around this lambda expression outer variable issue?

    - by panamack
    I'm playing with PropertyDescriptor and ICustomTypeDescriptor (still) trying to bind a WPF DataGrid to an object, for which the data is stored in a Dictionary. Since if you pass WPF DataGrid a list of Dictionary objects it will auto generate columns based on the public properties of a dictionary (Comparer, Count, Keys and Values) my Person subclasses Dictionary and implements ICustomTypeDescriptor. ICustomTypeDescriptor defines a GetProperties method which returns a PropertyDescriptorCollection. PropertyDescriptor is abstract so you have to subclass it, I figured I'd have a constructor that took Func and an Action parameters that delegate the getting and setting of the values in the dictionary. I then create a PersonPropertyDescriptor for each Key in the dictionary like this: foreach (string s in this.Keys) { var descriptor = new PersonPropertyDescriptor( s, new Func<object>(() => { return this[s]; }), new Action<object>(o => { this[s] = o; })); propList.Add(descriptor); } The problem is that each property get's its own Func and Action but they all share the outer variable s so although the DataGrid autogenerates columns for "ID","FirstName","LastName", "Age", "Gender" they all get and set against "Gender" which is the final resting value of s in the foreach loop. How can I ensure that each delegate uses the desired dictionary Key, i.e. the value of s at the time the Func/Action is instantiated? Much obliged. Here's the rest of my idea, I'm just experimenting here these are not 'real' classes... // DataGrid binds to a People instance public class People : List<Person> { public People() { this.Add(new Person()); } } public class Person : Dictionary<string, object>, ICustomTypeDescriptor { private static PropertyDescriptorCollection descriptors; public Person() { this["ID"] = "201203"; this["FirstName"] = "Bud"; this["LastName"] = "Tree"; this["Age"] = 99; this["Gender"] = "M"; } //... other ICustomTypeDescriptor members... public PropertyDescriptorCollection GetProperties() { if (descriptors == null) { var propList = new List<PropertyDescriptor>(); foreach (string s in this.Keys) { var descriptor = new PersonPropertyDescriptor( s, new Func<object>(() => { return this[s]; }), new Action<object>(o => { this[s] = o; })); propList.Add(descriptor); } descriptors = new PropertyDescriptorCollection(propList.ToArray()); } return descriptors; } //... other other ICustomTypeDescriptor members... } public class PersonPropertyDescriptor : PropertyDescriptor { private Func<object> getFunc; private Action<object> setAction; public PersonPropertyDescriptor(string name, Func<object> getFunc, Action<object> setAction) : base(name, null) { this.getFunc = getFunc; this.setAction = setAction; } // other ... PropertyDescriptor members... public override object GetValue(object component) { return getFunc(); } public override void SetValue(object component, object value) { setAction(value); } }

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  • Update on: How to model random non-overlapping spheres of non-uniform size in a cube using Matlab?

    - by user3838079
    I am trying to use MATLAB for generating random locations for non-uniform size spheres (non-overlapping) in a cube. The for loop in the code below never seems to end. I don't know what am missing in the code. I have ran the code for no. of spheres (n) = 10; dims = [ 10 10 10 ] function [ c r ] = randomSphere( dims ) % creating one sphere at random inside [0..dims(1)]x[0..dims(2)]x... % radius and center coordinates are sampled from a uniform distribution % over the relevant domain. % output: c - center of sphere (vector cx, cy,... ) % r - radius of sphere (scalar) r = rand(1); % you might want to scale this w.r.t dims or other consideration c = r + rand( size(dims) )./( dims - 2*r ); % make sure sphere does not exceed boundaries function ovlp = nonOverlapping( centers, rads ) % check if several spheres with centers and rads overlap or not ovlp = false; if numel( rads ) == 1 return; % nothing to check for a single sphere end dst = sqrt( sum( bsxfun( @minus, permute( centers, [1 3 2] ),... permute( centers, [3 1 2] ) ).^2, 3) ); ovlp = dst >= bsxfun( @plus, rads, rads.' ); %' all distances must be smaller than r1+r2 ovlp = any( ovlp(:) ); % all must not overlap function [centers rads] = sampleSpheres( dims, n ) % dims is assumed to be a row vector of size 1-by-ndim % preallocate ndim = numel(dims); centers = zeros( n, ndim ); rads = zeros( n, 1 ); ii = 1; while ii <= n [centers(ii,:), rads(ii) ] = randomSphere( dims ); if nonOverlapping( centers(1:ii,:), rads(1:ii) ) ii = ii + 1; % accept and move on end end

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  • What sort of object is this and how to use it?

    - by Gary
    What would be the correct name for this type of array? There are 3 main sections and 4 sub-parts consisting of "issuedTime" "text" "url" and "validToTime", how do you start to convert this to an object? If there was only 1 main section, it would be fairly simple to do however with 3 main parts and no identification for each main section has me scratching my head as where to start. Any advise appreciated. [{ "issuedTime":"7:13pm Sunday 13 June 2010", "text":"\nAmended 7:10pm.\n\nText text and more text\n", "url":"\/folder\/fc\/name.png", "validToTime":"12:00am Monday 14 June 2010" },{ "issuedTime":"8:33pm Sunday 13 June 2010", "text":"\nText and more text.\n", "url":"\/folder\/fc\/name.png", "validToTime":"12:00pm Monday 14 June 2010" },{ "issuedTime":"10:40am Sunday 13 June 2010", "text":"\nAnd even more text.", "url":"\/folder\/fc\/name.png", "validToTime":"12:00am Tuesday 15 June 2010" } ]

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  • Counting array in API JSON Response

    - by bryan
    I'm trying to do a simple count of how many refunds are in my Stripe Response but count() isn't working and I don't really know any other way of achieving this. Could anyone point me in the right direction? $retrieve_event = Stripe_Event::retrieve("evt_00000000000000"); $event_json_id = json_decode($retrieve_event); $refund_array = $event_json_id->{'data'}->{'object'}->{'refunds'}; die(count($refund_array)); This is the response of $retrieve_event { "created": 1326853478, "livemode": false, "id": "evt_00000000000000", "type": "charge.refunded", "object": "event", "request": null, "data": { "object": { "id": "ch_00000000000000", "object": "charge", "created": 1402433517, "livemode": false, "paid": true, "amount": 1000, "currency": "usd", "refunded": true, "card": { "id": "card_00000000000000", "object": "card", "last4": "0028", "type": "Visa", "exp_month": 8, "exp_year": 2015, "fingerprint": "a5KWlTcrmCYk5DIYa", "country": "US", "name": "First Last", "address_line1": "null", "address_line2": null, "address_city": "null", "address_state": "null", "address_zip": "null", "address_country": "US", "cvc_check": null, "address_line1_check": "fail", "address_zip_check": "pass", "customer": "cus_00000000000000" }, "captured": true, "refunds": [ { "id": "re_104CKt4uGeYuVLAahMwLA2TK", "amount": 100, "currency": "usd", "created": 1402433533, "object": "refund", "charge": "ch_104CKt4uGeYuVLAazSyPqqLV", "balance_transaction": "txn_104CKt4uGeYuVLAaSNZCR867", "metadata": {} }, { "id": "re_104CKt4uGeYuVLAaDIMHoIos", "amount": 200, "currency": "usd", "created": 1402433539, "object": "refund", "charge": "ch_104CKt4uGeYuVLAazSyPqqLV", "balance_transaction": "txn_104CKt4uGeYuVLAaqSwkNKPO", "metadata": {} }, { "id": "re_4CL6n1r91dY5ME", "amount": 700, "currency": "usd", "created": 1402434306, "object": "refund", "charge": "ch_4CL6FNWhGzVuAV", "balance_transaction": "txn_4CL6qa4vwlVaDJ" } ], "balance_transaction": "txn_00000000000000", "failure_message": null, "failure_code": null, "amount_refunded": 1000, "customer": "cus_00000000000000", "invoice": null, "description": "this is a description", "dispute": null, "metadata": {}, "statement_description": "this is a description", "fee": 0 } } }

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  • django integrate htmls into templates

    - by dana
    hi guys, i have a django 'templating' question if i have in views.py: def cv(request): if request.user.is_authenticated(): cv = OpenCv.objects.filter(created_by=request.user) return render_to_response('cv/cv.html', { 'object_list': cv, }, context_instance=RequestContext(request)) and in cv.html something like: {% for object in object_list %} First Name {{ object.first_name }} Last Name {{ object.last_name }} Url {{object.url}} Picture {{object.picture}} Bio {{object.bio}} Date of birth {{object.date_birth}} {% endfor %} but i want this content to appear on the profile.html page too, how can i do it? a smple {% include cv.html %} in the profile.html doesn't work. Also, is there another way to 'parse the object list' than explicitly write all the objects, like above? thanks in advance!

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  • Program-wide data, C++

    - by bobobobo
    I'd like to make program-wide data in a C++ program. The easiest way to do it in C# is just public static members. C#: public static class DataContainer { public static Object data1 ; public static Object data2 ; } In C++ you can do the same thing C++ global data way#1: class DataContainer { public: static Object data1 ; static Object data2 ; } ; Object DataContainer::data1 ; Object DataContainer::data2 ; However there's also extern C++ global data way #2: class DataContainer { public: Object data1 ; Object data2 ; } ; extern DataContainer * dataContainer ; // instantiate in .cpp file Which is better, or possibly another way which I haven't thought about?

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  • how do you get the response back into the instance of the object?

    - by randomdev
    If you've written a class in JavaScript that calls a remote service's API, and that remote API offers a callback, how do you get the response back into the instance of the object that made the request? I'll try to give you a very basic example FOO for making cross domain calls to BAR service which offers a callback. Please ignore the usual security concerns, (I own both servers). function FOO() { this.response = null; this.execute = function(url) { var script = document.createElement('script'); script.src = url; document.getElementsByTagName('head')[0].appendChild(script); } this.catch = function(response) { this.response = response; } } var sample = new FOO(); sample.execute('http://barservices.com/sample/?callback={ plshelphere: this.catch}'); I have a way to make this work, but I'm curious if there is an "accepted approach" here. Anyone have thoughts for me?

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  • Setting custom HTTP request headers in an URL object doesn't work.

    - by Blagovest Buyukliev
    I am trying to fetch an image from an IP camera using HTTP. The camera requires HTTP basic authentication, so I have to add the corresponding request header: URL url = new URL("http://myipcam/snapshot.jpg"); URLConnection uc = url.openConnection(); uc.setRequestProperty("Authorization", "Basic " + new String(Base64.encode("user:pass".getBytes()))); // outputs "null" System.out.println(uc.getRequestProperty("Authorization")); I am later passing the url object to ImageIO.read(), and, as you can guess, I am getting an HTTP 401 Unauthorized, although user and pass are correct. What am I doing wrong? I've also tried new URL("http://user:pass@myipcam/snapshot.jpg"), but that doesn't work either.

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  • Rails 3: How to validate that A < B where A and B are both model attributes ?

    - by Misha Moroshko
    I would like to validate that customer_price >= my_price. I tried the following: class Product < ActiveRecord::Base attr_accessor :my_price validates_numericality_of :customer_price, :greater_than_or_equal_to => my_price ... end (customer_price is a column in the Products table in the database, while my_price isn't.) Here is the result: NameError in ProductsController#index undefined local variable or method `my_price' for #<Class:0x313b648> What is the right way to do this in Rails 3 ?

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  • How do you call a method for an Objective-C object's superclass from elsewhere?

    - by executor21
    If you're implementing a subclass, you can, within your implementation, explicitly call the superclass's method, even if you've overridden that method, i.e.: [self overriddenMethod]; //calls the subclass's method [super overriddenMethod]; //calls the superclass's method What if you want to call the superclass's method from somewhere outside the subclass's implementation, i.e.: [[object super] overriddenMethod]; //crashes Is this even possible? And by extension, is it possible to go up more than one level within the implementation, i.e.: [[super super] overriddenMethod]; //will this work?

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  • Is it a good practice to pass struct object as parameter to a function in c++?

    - by tsubasa
    I tried an example live below: typedef struct point { int x; int y; } point; void cp(point p) { cout<<p.x<<endl; cout<<p.y<<endl; } int main() { point p1; p1.x=1; p1.y=2; cp(p1); } The result thats printed out is: 1 2 which is what I expected. My question is: Does parameter p get the full copy of object p1? If so, I wonder if this is a good practice? (I assumed when the struct gets big in size, this will create a lot of copy overhead).

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  • MySQL: check whether two fields on a model are always the same?

    - by AP257
    Sorry if this is a duplicate question, I'm a total database newbie and I'm probably using the wrong terminology to search for answers. I have a MySQL table as follows: +------------+---------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +------------+---------------+------+-----+---------+-------+ | placeid | int(11) | NO | PRI | NULL | | | grid | varchar(120) | YES | | NULL | | | vill | varchar(300) | YES | | NULL | | +------------+---------------+------+-----+---------+-------+ I'd like to find out whether 'grid' and 'vill' always occur in the same combinations or not. Maybe it'd be clearer with an example: placeid, grid, vill 1, TM1, Suffolk 2, TM1, Suffolk 3, WA8, Newcastle 4, WA8, Newcastle 5, WA8, York I'd like to construct a query that returns 'WA8' but not 'TM1', because 'WA8' occurs in combination with more than one vill. I would be SO grateful for any help!

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  • C# - What is root reference ?

    - by DotNetGuy
    class GCTest { static Object r1; static void Main() { r1 = new Object(); Object r2 = new Object(); Object r3 = new Object(); System.GC.Collect(); // what can be reclaimed here ? r1 = null; r3.ToString(); System.GC.Collect(); // what can be reclaimed here ? } } // code from - DonBox's Essential .Net

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  • How to get jSon object in servlet from jsp?

    - by divi
    In jsp page i have written: var sel = document.getElementById("Wimax"); var ip = sel.options[sel.selectedIndex].value; var param; var url = 'ConfigurationServlet?ActionID=Configuration_Physical_Get'; httpRequest = new ActiveXObject("Microsoft.XMLHTTP"); httpRequest.open("POST", url, true); httpRequest.onreadystatechange = handler(){ if (httpRequest.readyState == 4) { if (httpRequest.status == 200) { param = 'ip='+ip; param += 'mmv='+mmv; param += "tab="+tab; }}; httpRequest.send(param); i want this param variable in my configurationServlet. Can any one tel me how to get this json object in servlet???

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  • Do I have to worry about escaping XML reserved characters before I return a DataContract object from

    - by Brett Widmeier
    Hi, I am pretty inexperienced with WCF. I have a DataContract that implements the IExtensibleDataObject interface. Some of the members of this object are populated from freetext input and could contain XML reserved characters ('', for example). I imagine that I get escaping of these characters for free with WCF, but I have been looking around and could not find anything commenting on this one way or another. Is this the case? I have set my service to log the messages that it sends and receives for viewing in the Trace Viewer. Part of a message that my service returns looks like this: <sInstructions>"></sInstructions> Now, I have a couple questions about this. 1) Is it actually transmitting "&gt; and just showing it in a more readable form in the trace viewer? 2) If it is actually is transmitting ">, is this legal XML?

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  • What is the pythonic way to add type information to an object's attributes?

    - by Tikitu
    I'm building classes where I know the types of the attributes, but Python of course doesn't. While it's un-pythonic to want to tell it, supposing I do want to, is there an idiomatic way to do so? Why: I'm reading in serialised data (without type information) involving objects-nested-inside-objects. It's easy to put it into nested dictionaries, but I want it in objects of my class-types, to get the right behaviours as well as the data. For instance: suppose my class Book has an attribute isbn which I will fill with an ISBNumber object. My serialised data gives me the isbn as a string; I would like to be able to look at Book and say "That field should be filled by ISBNumber(theString)." Bonus glee for me if the solution can be applied to classes I get from someone else without editing their code.

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  • How do I go about link web content in a database with a nested set model?

    - by wb
    My nested set table is as follows. create table depts ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) , abbrv nvarchar(20) ); Test departments. insert into depts (lft, rgt, name, abbrv) values (1, 14, 'root', 'r'); insert into depts (lft, rgt, name, abbrv) values (2, 3, 'department 1', 'd1'); insert into depts (lft, rgt, name, abbrv) values (4, 5, 'department 2', 'd2'); insert into depts (lft, rgt, name, abbrv) values (6, 13, 'department 3', 'd3'); insert into depts (lft, rgt, name, abbrv) values (7, 8, 'sub department 3.1', 'd3.1'); insert into depts (lft, rgt, name, abbrv) values (9, 12, 'sub department 3.2', 'd3.2'); insert into depts (lft, rgt, name, abbrv) values (10, 11, 'sub sub department 3.2.1', 'd3.2.1'); My web content table is as follows. create table content ( id int identity(0, 1) , dept_id int , page_name nvarchar(60) , content ntext ); Test content. insert into content (dept_id, page_name, content) values (3, 'index', '<h2>welcome to department 3!</h2>'); insert into content (dept_id, page_name, content) values (4, 'index', '<h2>welcome to department 3.1!</h2>'); insert into content (dept_id, page_name, content) values (6, 'index', '<h2>welcome to department 3.2.1!</h2>'); insert into content (dept_id, page_name, content) values (2, 'what-doing', '<h2>what is department 2 doing?/h2>'); I'm trying to query the correct page content (from the content table) based on the url given. I can easily accomplish this task with a root department. However, querying a department with multiple depths is proving to be a little harder. For example: http://localhost/departments.asp?d3/ (Should return <h2>welcome to department 3!</h2>) http://localhost/departments.asp?d2/what-doing (Should return <h2>what is department 2 doing?</h2>) I'm not sure if this can be create in one query or if there will need to be a recursive function of some sort. Also, if there is nothing after the last / then assume we want the index page. How can this be accomplished? Thank you.

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