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• sql query - how to apply limit within group by

  - by Raj

  hey guys assuming i have a table named t1 with following fields: ROWID, CID, PID, Score, SortKey it has the following data: 1, C1, P1, 10, 1 2, C1, P2, 20, 2 3, C1, P3, 30, 3 4, C2, P4, 20, 3 5, C2, P5, 30, 2 6, C3, P6, 10, 1 7, C3, P7, 20, 2 what query do i write so that it applies group by on CID, but instead of returning me 1 single result per group, it returns me a max of 2 results per group. also where condition is score = 20 and i want the results ordered by CID and SortKey. If I had to run my query on above data, i would expect the following result: RESULTS FOR C1 - note: ROWID 1 is not considered as its score < 20 C1, P2, 20, 2 C1, P3, 30, 3 RESULTS FOR C2 - note: ROWID 5 appears before ROWID 4 as ROWID 5 has lesser value SortKey C2, P5, 30, 2 C2, P4, 20, 3 RESULTS FOR C3 - note: ROWID 6 does not appear as its score is less than 20 so only 1 record returned here C3, P7, 20, 2 IN SHORT, I WANT A LIMIT WITHIN A GROUP BY. I want the simplest solution and want to avoid temp tables. sub queries are fine. also note i am using sqlite for this

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• SQL: Need help with query construction.

  - by Geeknidas

  Hi Guys, I am relatively new with sql and I need some help with some basic query construction. Problem: To retrieve the number of orders and the customer id from a table based on a set of parameters. I want to write a query to figure out the number of orders under each customer (Column: Customerid) along with the CustomerID where the number of orders should be greater or equal to 10 and the status of the order should be Active. Moreover, I also want to know the first transaction date of an order belonging to each customerid. Table Description: product_orders Orderid CustomerId Transaction_date Status ------- ---------- ---------------- ------- 1 23 2-2-10 Active 2 22 2-3-10 Active 3 23 2-3-10 Deleted 4 23 2-3-10 Active Query that I have written: select count(*), customerid from product_orders where status = 'Active' GROUP BY customerid ORDER BY customerid; The above statement gives me the sum of all order under a customer id but does not fulfil the condition of atleast 10 orders. I donot know how to display the first transaction date along with the order under a customerid (status: could be active or delelted doesn't matter) Ideal solutions should look like: Total Orders CustomerID Transaction Date (the first transaction date) ------------ ---------- ---------------- 11 23 1-2-10 Thanks in advance. I hope you guys would be kind enough to stop by and help me out. Cheers, Leonidas

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• How do I stop the m2eclipse plugin interfering with command line mvn builds?

  - by locka

  I use the m2eclipse plugin in Eclipse so that I can import a Maven project. The plugin reads the pom.xml and sorts out the dependencies in the projects in an Eclipse friendly way so I'm not looking at a sea of broken references and errors. I use Eclipse for code development however I usually build the projects from the command line, e.g. "mvn clean install". Unfortunately when I do this, m2eclipse detects disk activity and attempts to rebuild the workspace. This interferes with the command line build and sometimes results in a race condition. For example the command line might be in its clean phase but fails because it tries to delete a file or directory which is locked during the workspace rebuild. Aside from that workspace rebuilding is incredibly slow, and between failed builds and wasted CPU my build process is 2-3x longer than it should be. It isn't an option to not use Eclipse (e.g. to use Netbeans), or to disable m2eclipse. It is a useful plugin except for this behaviour. So my question is, how do I stop m2eclipse from rebuilding the workspace all the time? Can I invoke a manual refresh and otherwise disable this behaviour?

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• SQL Concurrent test update question

  - by ptoinson

  Howdy Folks, I have a SQLServer 2008 database in which I have a table for Tags. A tag is just an id and a name. The definition of the tags table looks like: CREATE TABLE [dbo].[Tag]( [ID] [int] IDENTITY(1,1) NOT NULL, [Name] [varchar](255) NOT NULL CONSTRAINT [PK_Tag] PRIMARY KEY CLUSTERED ( [ID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ) Name is also a unique index. further I have several processes adding data to this table at a pretty rapid rate. These processes use a stored proc that looks like: ALTER PROC [dbo].[lg_Tag_Insert] @Name varchar(255) AS DECLARE @ID int SET @ID = (select ID from Tag where Name=@Name ) if @ID is null begin INSERT Tag(Name) VALUES (@Name) RETURN SCOPE_IDENTITY() end else begin return @ID end My issues is that, other than being a novice at concurrent database design, there seems to be a race condition that is causing me to occasionally get an error that I'm trying to enter duplicate keys (Name) into the DB. The error is: Cannot insert duplicate key row in object 'dbo.Tag' with unique index 'IX_Tag_Name'. This makes sense, I'm just not sure how to fix this. If it where code I would know how to lock the right areas. SQLServer is quite a different beast. First question is what is the proper way to code this 'check, then update pattern'? It seems I need to get an exclusive lock on the row during the check, rather than a shared lock, but it's not clear to me the best way to do that. Any help in the right direction will be greatly appreciated. Thanks in advance.

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• How do I fetch a set of rows from data table

  - by cmrhema

  Hi, I have a dataset that has two datatables. In the first datatable I have EmpNo,EmpName and EmpAddress In the second datatable I have Empno,EmpJoindate, EmpSalary. I want a result where I should show EmpName as the label and his/her details in the gridview I populate a datalist with the first table, and have EmpNo as the datakeys. Then I populate the gridview inside the datatable which has EmpNo,EmpJoinDate and EmpAddress. My code is some what as below Datalist1.DataSource = dt; Datalist1.DataBind(); for (int i = 0; i < Datalist1.Items.Count; i++) { int EmpNo = Convert.ToInt32(Datalist1.DataKeys[i]); GridView gv = (GridView)Datalist1.FindControl("gv"); gv.DataSource = dt2; gv.DataBind(); } Now I have a problem, I have to bind the Details of the corresponding Employee to the gridview. Whereas the above code will display all the details of all employees in the gridview. If we use IEnumerable we give a condition where(a=a.eno=EmpNo), and bind that list to the gridview. How do I do this in datatable. kindly do not give me suggestions of altering the stored procedure which results the values in two tables, because that cannot be altered. I have to find a solution within the existing objects I have. Regards Hema

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• verilog / systemverilog -- What is the behavior of blocking statements across two always blocks?

  - by miles.sherman

  I am wondering about the behavior of the below code. There are two always blocks, one is combinational to calculate the next_state signal, the other is sequential which will perform some logic and determine whether or not to shutdown the system. It does this by setting the shutdown_now signal high and then calling state <= next_state. My question is if the conditions become true that the shutdown_now signal is set (during clock cycle n) in a blocking manner before the state <= next_state line, will the state during clock cycle n+1 be SHUTDOWN or RUNNING? In other words, does the shutdown_now = 1'b1 line block across both state machines since the state signal is dependent on it through the next_state determination? enum {IDLE, RUNNING, SHUTDOWN} state, next_state; logic shutdown_now; // State machine (combinational) always_comb begin case (state) IDLE: next_state <= RUNNING; RUNNING: next_state <= shutdown ? SHUTDOWN : RUNNING; SHUTDOWN: next_state <= SHUTDOWN; default: next_state <= SHUTDOWN; endcase end // Sequential Behavior always_ff @ (posedge clk) begin // Some code here if (/*some condition) begin shutdown_now = 1'b0; end else begin shutdown_now = 1'b1; end state <= next_state; end

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• How to generate random numbers of lognormal distribution within specific range in Matlab

  - by Harpreet

  My grain sizes are defined as D=[1.19,1.00,0.84,0.71,0.59,0.50,0.42]. The problem is described below in steps. Grain sizes should follow lognormal distribution. The mean of the grain sizes is fixed as 0.84 and the standard deviation should be as low as possible but not zero. 90% of the grains (by weight %) fall in the size range of 1.19 to 0.59, and the rest 10% fall in size range of 0.50 to 0.42. Now I want to find the probabilities (weight percentage) of the grains falling in each grain size. It is allowable to split this grain size distribution into further small sizes but it must always be in the range of 1.19 and 0.42, i.e. 'D' can be continuous but 0.42 < D < 1.19. I need it fast. I tried on my own but I am not able to get the correct result. I am getting negative probabilities (weight percentages). Thanks to anyone who helps. I didn't incorporate the point 3 as I came to know about that condition later. Here are simple steps I tried: %% D=[1.19,1.00,0.84,0.71,0.59,0.50,0.42]; s=0.30; % std dev of the lognormal distribution m=0.84; % mean of the lognormal distribution mu=log(m^2/sqrt(s^2+m^2)); % mean of the associated normal dist. sigma=sqrt(log((s^2/m^2)+1)); % std dev of the associated normal dist. [r,c]=size(D); for i=1:c D(i)=mu+(sigma.*randn(1)); w(i)=(log(D(i))-mu)/sigma; % the probability or the wt. percentage of the grain sizes end grain_size=exp(D); %%

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• Are dots legal in the name property of an HTML button

  - by justSteve

  a page with a bit of MVC code: <%=Html.SubmitButton("ChooseWebinar.Submit", "Continue to Registration Details")%><br/> that generates an input button where the '.' is embedded in the name: [rendered html] At page load this control (the submit button) is hidden - when one of two different dropdowns registers a value, the button is shown: function toggleChooseWebinarSubmit() { if ($("#ChooseWebinar_RecordedWebinarId").val() || $("#ChooseWebinar_UpcomingWebinarId").val()) { $("#ChooseWebinar_Submit").show(); } else { $("#ChooseWebinar_Submit").hide(); } I've just received a report from an IE8 user who says that after selecting a value in a dropdown, the button is _not displaying. I can't reproduce the condition (i've tried compatibility mode too). Obviously the show/hide is targeting the 'ID' selector but i can't help but wonder about that period in the control's name. Any known issues? - or perhaps the .change is problematic and the toggle's never getting called: $(window).load(function() { toggleChooseWebinarSubmit(); $("#ChooseWebinar_UpcomingWebinarId").change(function() { if ($(this).val()) { $("#ChooseWebinar_RecordedWebinarId").val(""); } toggleChooseWebinarSubmit(); }); $("#ChooseWebinar_RecordedWebinarId").change(function() { if ($(this).val()) { $("#ChooseWebinar_UpcomingWebinarId").val(""); } toggleChooseWebinarSubmit(); }); }); thx

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• Why doesn't gcc remove this check of a non-volatile variable?

  - by Thomas

  This question is mostly academic. I ask out of curiosity, not because this poses an actual problem for me. Consider the following incorrect C program. #include <signal.h> #include <stdio.h> static int running = 1; void handler(int u) { running = 0; } int main() { signal(SIGTERM, handler); while (running) ; printf("Bye!\n"); return 0; } This program is incorrect because the handler interrupts the program flow, so running can be modified at any time and should therefore be declared volatile. But let's say the programmer forgot that. gcc 4.3.3, with the -O3 flag, compiles the loop body (after one initial check of the running flag) down to the infinite loop .L7: jmp .L7 which was to be expected. Now we put something trivial inside the while loop, like: while (running) putchar('.'); And suddenly, gcc does not optimize the loop condition anymore! The loop body's assembly now looks like this (again at -O3): .L7: movq stdout(%rip), %rsi movl $46, %edi call _IO_putc movl running(%rip), %eax testl %eax, %eax jne .L7 We see that running is re-loaded from memory each time through the loop; it is not even cached in a register. Apparently gcc now thinks that the value of running could have changed. So why does gcc suddenly decide that it needs to re-check the value of running in this case?

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• Advice on Method overloads.

  - by Muhammad Kashif Nadeem

  Please see following methods. public static ProductsCollection GetDummyData(int? customerId, int? supplierId) { try { if (customerId != null && customerId > 0) { Filter.Add(Customres.CustomerId == customerId); } if (supplierId != null && supplierId > 0) { Filter.Add(Suppliers.SupplierId == supplierId); } ProductsCollection products = new ProductsCollection(); products.FetchData(Filter); return products; } catch { throw; } } public static ProductsCollection GetDummyData(int? customerId) { return ProductsCollection GetDummyData(customerId, (int?)null); } public static ProductsCollection GetDummyData() { return ProductsCollection GetDummyData((int?)null); } 1- Please advice how can I make overloads for both CustomerId and SupplierId because only one overload can be created with GetDummyData(int? ). Should I add another argument to mention that first argument is CustomerId or SupplierId for example GetDummyData(int?, string). OR should I use enum as 2nd argument and mention that first argument is CustoemId or SupplierId. 2- Is this condition is correct or just checking 0 is sufficient - if (customerId != null && customerId 0) 3- Using Try/catch like this is correct? 4- Passing (int?)null is correct or any other better approach. Edit: I have found some other posts like this and because I have no knowledge of Generics that is why I am facing this problem. Am I right? Following is the post. http://stackoverflow.com/questions/422625/overloaded-method-calling-overloaded-method

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• Has form post behavior changed in modern browsers? (or How are double clicks handled by the browser)

  - by Alex Czarto

  Background: We are in the process of writing a registration/payment page, and our philosophy was to code all validation and error checking on the server side first, and then add client side validation as a second step (un-obstructive jQuery). We wanted to disable double clicks server side, so we wrote some locking, thread-safe code to handle simultaneous posts/race conditions. When we tried to test this, we realized that we could not cause a simultaneous post or race condition to occur. I thought that (in older browsers anyway) double clicking a submit button worked as follows: User double clicks submit button. Browser sends a post on the first click On the second click, browser cancels/ignores initial post, and initiates a second post (before the first post has returned with a response). Browser waits for second post to return, ignoring initial post response. I thought that from the server side it looked like this: Server gets two simultaneous post requests, executes and responds to them both (unaware that no one is listening to the first response). From our testing (FireFox 3.0, IE 8.0) this is what actually happens: User double clicks submit button Browser sends a post for the first click Browser queues up second click, but waits for the response from the first click. Response returns from first click (response is ignored?). Browser sends a post for the second click. So from a server side: Server receives a single post which it executes and responds to. Then, server receives a second request wich it executes and responds to. My question is, has this always worked this way (and I'm losing my mind)? Or is this a new feature in modern browsers that prevents simultaneous posts to be sent to the server? It seems that for server side double click prevention, we don't have to worry about simultaneous posts or race conditions. Only need to worry about queued up posts. Thanks in advance for any feedback / comments. Alex

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• "hour" int taken from NSDate not behaving as expected at midnight??

  - by Eric

  I feel like I've lost my mind. Can someone tell me what's going on here? Also, I'm sure there is a better way to do what I'm trying to do, but I'm not interested in that now. I'd just like to solve the mystery of why my ints are not responding to logic as expected. // Set "At: " field close to current time NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; [dateFormatter setDateFormat:@"HH"]; int hour = [[dateFormatter stringFromDate:[NSDate date]] intValue]; [dateFormatter setDateFormat:@"mm"]; int minute = [[dateFormatter stringFromDate:[NSDate date]] intValue]; NSLog(@"currently %i:%i",hour, minute); if(hour >= 12){ // convert to AM/PM selectedMeridiem = 1; if(hour != 12){ hour = hour - 12; } } else{ selectedMeridiem = 0; } selectedHour = hour - 1; if(selectedHour <= 0){ selectedHour = 11; } When I debug the above code with my clock set to 12:XX AM, the integer "hour" returned is 0. But then any if statements with the condition if(hour == 0) are not evaluated. Likewise, this would not be evaluated either: if(hour < 1). The code above puts the hour int into another int, selectedHour (don't worry about why I'm doing this for now), but selectedHour suffers from the same weird behavior; the if(selectedHour <= 0) line is never evaluated. Am I going crazy, or am I just an idiot? Maybe there's some behavior of 0 integers that I'm not aware of. All of my code runs fine as long as it's not 12:XX AM.

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• Dealing with Try/Catch Exceptions in Java bytecode? ("stack height inconsistent")

  - by Cogwirrel

  I am trying to do some error handling in java bytecode. I first tried to implement some catch-like subroutines, where I would check for the error condition, and jump to the appropriate subroutine, a little like: iconst_1 iconst_0 dup ifeq calldiverr goto enddivtest calldiverr: jsr divError enddivtest: idiv ...More instructions... divError: getstatic java/lang/System/out Ljava/io/PrintStream; ldc "Oh dear you divided by 0!" invokevirtual java/io/PrintStream/print(Ljava/lang/String;)V The problem with the above is that when I have multiple instructions that jump to this subroutine, I get an error message when running the bytecode, saying that the stack height is inconsistent. Perhaps using exceptions is the best way to get around this? From some googling I have found that you can create instances of Exception classes and initialise them with something like: new java/lang/Exception dup ldc "exception message!" invokespecial java/lang/Exception/<init>(Ljava/lang/String;)V I have also found that you can throw them with athrow and this seems ok. What is confusing me however is exactly how exceptions are caught. There seems to be a magical "Exception table" which glues the throwing and catching of exceptions together, but I do not know how to define one of these when writing bytecode from scratch (and assembling using Jasmin). Can somebody tell me the secret of creating an exception table? And possibly give me an example of exception handling that will assemble with jasmin?

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• Lightweight alternative to Manual/AutoResetEvent in C#

  - by sweetlilmre

  Hi, I have written what I hope is a lightweight alternative to using the ManualResetEvent and AutoResetEvent classes in C#/.NET. The reasoning behind this was to have Event like functionality without the weight of using a kernel locking object. Although the code seems to work well in both testing and production, getting this kind of thing right for all possibilities can be a fraught undertaking and I would humbly request any constructive comments and or criticism from the StackOverflow crowd on this. Hopefully (after review) this will be useful to others. Usage should be similar to the Manual/AutoResetEvent classes with Notify() used for Set(). Here goes: using System; using System.Threading; public class Signal { private readonly object _lock = new object(); private readonly bool _autoResetSignal; private bool _notified; public Signal() : this(false, false) { } public Signal(bool initialState, bool autoReset) { _autoResetSignal = autoReset; _notified = initialState; } public virtual void Notify() { lock (_lock) { // first time? if (!_notified) { // set the flag _notified = true; // unblock a thread which is waiting on this signal Monitor.Pulse(_lock); } } } public void Wait() { Wait(Timeout.Infinite); } public virtual bool Wait(int milliseconds) { lock (_lock) { bool ret = true; // this check needs to be inside the lock otherwise you can get nailed // with a race condition where the notify thread sets the flag AFTER // the waiting thread has checked it and acquires the lock and does the // pulse before the Monitor.Wait below - when this happens the caller // will wait forever as he "just missed" the only pulse which is ever // going to happen if (!_notified) { ret = Monitor.Wait(_lock, milliseconds); } if (_autoResetSignal) { _notified = false; } return (ret); } } }

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• Getting exception when trying to monkey patch pymongo.connection._Pool

  - by Creotiv

  I use pymongo 1.9 on Ubuntu 10.10 with python 2.6.6 When i trying to monkey patch pymongo.connection._Pool i'm getting error on connection: AutoReconnect: could not find master/primary But when i change _Pool class in pymongo.connection module, it work pretty fine. Even if i copy _Pool implementation from pymongo.connection module and will try to monkey patch by the same code, it still giving same exception. I need to remove threading.local from _Pool class, because i use gevent and i need to implement Pool for all mongo connections(for all threads). I use this code: import pymongo class GPool: """A simple connection pool. Uses thread-local socket per thread. By calling return_socket() a thread can return a socket to the pool. Right now the pool size is capped at 10 sockets - we can expose this as a parameter later, if needed. """ # Non thread-locals __slots__ = ["sockets", "socket_factory", "pool_size","sock"] #sock = None def __init__(self, socket_factory): self.pool_size = 10 if not hasattr(self,"sock"): self.sock = None self.socket_factory = socket_factory if not hasattr(self, "sockets"): self.sockets = [] def socket(self): # we store the pid here to avoid issues with fork / # multiprocessing - see # test.test_connection:TestConnection.test_fork for an example # of what could go wrong otherwise pid = os.getpid() if self.sock is not None and self.sock[0] == pid: return self.sock[1] try: self.sock = (pid, self.sockets.pop()) except IndexError: self.sock = (pid, self.socket_factory()) return self.sock[1] def return_socket(self): if self.sock is not None and self.sock[0] == os.getpid(): # There's a race condition here, but we deliberately # ignore it. It means that if the pool_size is 10 we # might actually keep slightly more than that. if len(self.sockets) < self.pool_size: self.sockets.append(self.sock[1]) else: self.sock[1].close() self.sock = None pymongo.connection._Pool = GPool

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• Easiest RPC client method in PHP

  - by T.K.

  I've been asked to help a friend's company to bring up a web application. I have very limited time and I reluctantly accepted the request, at one condition. As most of the logic goes on in the back-end, I suggested that I would finish the complete back-end only, allowing a front-end developer to simply interface with my backend. I plan to do the back-end in Java EE or Python (with Pylons). It does not really matter at this point. I plan to have my back-end completely ready and unit-tested, so that my input will hardly be needed after my work is done. I know they have a PHP programmer, but as far as I could tell he is a real rookie. I want him to basically interface with my backend's services in the easiest possible way, with no way of him "stuffing" it up. It's basically a CRUD-only application. I could implement the backend as accessible through a webservice such as XML-RPC or SOAP. Even a RESTful API could be possible. However, my main objective is to make something that complete "noob" PHP programmer can easily interface with without getting confused. Preferably I do not even want to talk to him because I generally have an extremely busy schedule, and doing "support calls" is not something I am willing to do. Which approach should I choose? I would welcome any suggestions and inputs!

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• Could my forms be hacked.

  - by Mike Sandman

  Hi there, I posted a question yesterday, which I intend to get back to today however I wrote some JavaScript as a first line of prevention against XSS. However when testing this on my live server I catch some invalid input as the javascript catches the php section. My form uses post and php isn't in my form items (i haven't typed it in). Could this be picking up the form action or something? I'm baffeled, Any ideas Here is my code, it is triggered on the submit button. function validateForBadNess(){ var theShit = new Array("*","^", "$", "(",")","{", "}","[", "]","\", "|", "'","/","?",",","=","","gt","lt", "<","script","`","´","php"); var tagName = new Array(); tagName[0] = "input"; tagName[1] = "select"; tagName[2] = "textbox"; tagName[3] = "textarea"; for (ms=0;ms // loop through the elements of the form var formItems = document.getElementsByTagName(tagName[ms]); for (var xs=0;xs var thisString = formItems[xs].value; // loop through bad array for (zs in theShit){ //alert(thisString + " " + thisString.indexOf(theShit[zs])) if(thisString.indexOf(theShit[zs]) >= 0){ alert("Sorry but the following character: " + theShit[zs] + " is not permitted. Please omit it from your input.\nIf this is part of your password please contact us to heave your password reset.") return false; } } // loop for formitems } // tagName toop } // original condition }

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• CheckBox won't toggle in Android ListView with focusable="false"

  - by user3563124

  I'm creating a ListView with a custom Adapter for displaying my entries. Each row contains a checkbox, and my adapter contains the following code: CheckBox cb = (CheckBox) v.findViewById(R.id.item_sold); cb.setChecked(p.isSold); setupCheckboxListener(cb, v, position); ... private void setupCheckboxListener(CheckBox check, final View v, final int position) { check.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { CheckBox cb = (CheckBox) v; if (cb.isChecked()) { System.out.println("Should become false!"); cb.setChecked(false); } else { System.out.println("Should become true!"); cb.setChecked(true); } } }); My row XML file includes the following: <CheckBox android:id="@+id/item_sold" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="0.10" android:layout_gravity="center" android:gravity="center" android:focusable="false" android:clickable="false"/> But anytime I press one of the checkboxes, check.isChecked() returns true, even if the box is unchecked. I even checked to make sure that the checkboxes were distinct and weren't picking up just the last value/etc. Setting up the listeners inline instead of in a method doesn't seem to help, either. It's literally just the isChecked() condition that isn't working appropriately - it seems to always give me the inverse value. Setting an onClick on the row is not acceptable in this case because I need to allow row selection for something else. What could be causing this issue?

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• Rails Active Record Mysql find query HAVING clause

  - by meetraghu28

  Is there a way to use the HAVING clause in some other way without using group by. I am using rails and following is a sample sccenario of the problem that i am facing. In rails you can use the Model.find(:all,:select,conditions,:group) function to get data. In this query i can specify a having clause in the :group param. But what if i dont have a group by clause but want to have a having clause in the result set. Ex: Lets take a query select sum(x) as a,b,c from y where "some_conditions" group by b,c; This query has a sum() aggregation on one of the fields. No if there is nothing to aggregate then my result should be an empty set. But mysql return a NULL row. So this problem can be solved by using select sum(x) as a,b from y where "some_conditions" group by b having a NOT NULL; but what happens in case i dont have a group by clause?? a query like below select sum(x) as a,b from y where "some_conditions"; so how to specify that sum(x) should not be NULL? Any solution that would return an empty set in this case instead of a NULL row will help and also that solution should be doable in rails. We can use subqueries to get this condition working with sumthin like this select * from ((select sum(x) as b FROM y where "some_condition") as subq) where subq.b is not null; but is there a better way to do this thru sql/rails ??

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• Which CMS do I need? Needs to be easy to post a certain kind of post

  - by Vian Esterhuizen

  Hi, I'm creating a site for a video store and it needs to be CMS. I'm doing this for free so I need to use a free CMS like Wordpress, Drupal or Joomla. Do I need a new CMS, a plugin or some PHP of my own? What I need: User accounts Categories Custom post Here's the site as it stands with WP: http://sundancevideo.ca. Right now an experimental site to try to work this out. What I've done now, is created a "Draft" that includes a template table with images and text and so on. The user would then have to copy everything, past into a new post and replace necessary. This really isn't working well. As you may notice by the condition of the posts. What I would prefer is if it was integrated into the WP UI. Like a field for "Description" and field for "Image" where they can upload the images as necessary. This would then generate post, with a table including all the information and images, for as many movies that were added in the UI. Please ask if I'm not being clear. Please help, any suggestions are welcome. Thank you, Vian

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• Replace .sln with MSBuild and wrap contained projects into targets

  - by Filburt

  I'd like to create a MSBuild project that reflects the project dependencies in a solution and wraps the VS projects inside reusable targets. The problem I like solve doing this is to svn-export, build and deploy a specific assembly (and its dependencies) in an BizTalk application. My question is: How can I make the targets for svn-exporting, building and deploying reusable and also reuse the wrapped projects when they are built for different dependencies? I know it would be simpler to just build the solution and deploy only the assemblies needed but I'd like to reuse the targets as much as possible. The parts The project I like to deploy <Project DefaultTargets="Deploy" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> <PropertyGroup> <ExportRoot Condition="'$(Export)'==''">Export</ExportRoot> </PropertyGroup> <Target Name="Clean_Export"> <RemoveDir Directories="$(ExportRoot)\My.Project.Dir" /> </Target> <Target Name="Export_MyProject"> <Exec Command="svn export svn://xxx/trunk/Biztalk2009/MyProject.btproj --force" WorkingDirectory="$(ExportRoot)" /> </Target> <Target Name="Build_MyProject" DependsOnTargets="Export_MyProject"> <MSBuild Projects="$(ExportRoot)\My.Project.Dir\MyProject.btproj" Targets="Build" Properties="Configuration=Release"></MSBuild> </Target> <Target Name="Deploy_MyProject" DependsOnTargets="Build_MyProject"> <Exec Command="BTSTask AddResource -ApplicationName:CORE -Source:MyProject.dll" /> </Target> </Project> The projects it depends upon look almost exactly like this (other .btproj and .csproj).

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• How do i select the preceding nodes of a text node starting from a specific node and not the root no

  - by Rachel

  How do i select the preceding nodes of a text node starting from a specific node whose id i know instead of getting the text nodes from the root node? When i invoke the below piece from a template match of text node, I get all the preceding text nodes from the root. I want to modify the above piece of code to select only the text nodes that appear after the node having a specific id say 123. i.e something like //*[@id='123'] <xsl:template match="text()[. is $text-to-split]"> <xsl:variable name="split-index" as="xsd:integer" select="$index - sum(preceding::text()/string-length(.))"/> <xsl:value-of select="substring(., 1, $split-index - 1)"/> <xsl:copy-of select="$new"/> <xsl:value-of select="substring(., $split-index)"/> </xsl:template> <xsl:variable name="text-to-split" as="text()?" select="descendant::text()[sum((preceding::text(), .)/string-length(.)) ge $index][1]"/> How do i include the condition in places where i use preceding::text inorder to select preceding text nodes relative to the specific node's id which i know?

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• SQLAlchemy - relationship limited on more than just the foreign key

  - by Marian

  I have a wiki db layout with Page and Revisions. Each Revision has a page_id referencing the Page, a page relationship to the referenced page; each Page has a all_revisions relationship to all its revisions. So far so common. But I want to implement different epochs for the pages: If a page was deleted and is recreated, the new revisions have a new epoch. To help find the correct revisions, each page has a current_epoch field. Now I want to provide a revisions relation on the page that only contains its revisions, but only those where the epochs match. This is what I've tried: revisions = relationship('Revision', primaryjoin = and_( 'Page.id == Revision.page_id', 'Page.current_epoch == Revision.epoch', ), foreign_keys=['Page.id', 'Page.current_epoch'] ) Full code (you may run that as it is) However this always raises ArgumentError: Could not determine relationship direction for primaryjoin condition ...`, I've tried all I had come to mind, it didn't work. What am I doing wrong? Is this a bad approach for doing this, how could it be done other than with a relationship?

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• Partially constructed object / Multi threading

  - by reto

  Heya! I'm using joda due to it's good reputation regarding multi threading. It goes great distances to make multi threaded date handling efficient, for example by making all Date/Time/DateTime objects immutable. But here's a situation where I'm not sure if Joda is really doing the right thing. It probably is correct, but I'd be very interested to see the explanation for it. When a toString() of a DateTime is being called Joda does the following: /* org.joda.time.base.AbstractInstant */ public String toString() { return ISODateTimeFormat.dateTime().print(this); } All formatters are thread safe, as they are as well ready-only. But what's about the formatter-factory: private static DateTimeFormatter dt; /* org.joda.time.format.ISODateTimeFormat */ public static DateTimeFormatter dateTime() { if (dt == null) { dt = new DateTimeFormatterBuilder() .append(date()) .append(tTime()) .toFormatter(); } return dt; } This is a common pattern in single threaded applications. I see the following dangers: Race condition during null check -- worst case: two objects get created. No Problem, as this is solely a helper object (unlike a normal singleton pattern situation), one gets saved in dt, the other is lost and will be garbage collected sooner or later. the static variable might point to a partially constructed object before the objec has been finished initialization (before calling me crazy, read about a similar situation in this Wikipedia article. So how does Joda ensure that not partially created formatter gets published in this static variable? Thanks for your explanations! Reto

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• How do I left join tables in unidirectional many-to-one in Hibernate?

  - by jbarz

  I'm piggy-backing off of http://stackoverflow.com/questions/2368195/how-to-join-tables-in-unidirectional-many-to-one-condition. If you have two classes: class A { @Id public Long id; } class B { @Id public Long id; @ManyToOne @JoinColumn(name = "parent_id", referencedColumnName = "id") public A parent; } B - A is a many to one relationship. I understand that I could add a Collection of Bs to A however I do not want that association. So my actual question is, Is there an HQL or Criteria way of creating the SQL query: select * from A left join B on (b.parent_id = a.id) This will retrieve all A records with a Cartesian product of each B record that references A and will include A records that have no B referencing them. If you use: from A a, B b where b.a = a then it is an inner join and you do not receive the A records that do not have a B referencing them. I have not found a good way of doing this without two queries so anything less than that would be great. Thanks.

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