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• SQL vs MySQL: Rules about aggregate operations and GROUP BY

  - by Phazyck

  In this book I'm currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given: Find the name and age of the oldest sailor. Consider the following attempt to answer this query: SELECT S.name, S.age FROM Sailors.S The intent is for this query to return not only the maximum age but also the name of the sailors having that age. However, this query is illegal in SQL--if the SELECT clause uses an aggregate operation, then it must use only aggregate operations unless the query contains a GROUP BY clause! Some time later while doing an exercise using MySQL, I faced a similar problem, and made a mistake similar to the one mentioned. However, MySQL didn't complain and just spit out some tables which later turned out not be what I needed. Is the query above really illegal in SQL, but legal in MySQL, and if so, why is that? In what situation would one need to make such a query?

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• Question of using static_cast on "this" pointer in a derived object to base class

  - by Johnyy

  Hi, this is an example taken from Effective C++ 3ed, it says that if the static_cast is used this way, the base part of the object is copied, and the call is invoked from that part. I wanted to understand what is happening under the hood, will anyone help? class Window { // base class public: virtual void onResize() { } // base onResize impl }; class SpecialWindow: public Window { // derived class public: virtual void onResize() { // derived onResize impl; static_cast<Window>(*this).onResize(); // cast *this to Window, // then call its onResize; // this doesn't work! // do SpecialWindow- } // specific stuff };

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• Drupal theme preprocess function - primary links and suckerfish menus

  - by slimcady

  I have a preprocess function that works fine when the menu is single level list. However I would like it to work w/ suckerfish menus. I want to add a class to the top level menu item so that I can style it. This is the code I used for the single level menu: function cti_flex_preprocess_page(&$vars, $hook) { // Make a shortcut for the primary links variables $primary_links = $vars['primary_links']; // Loop thru the menu, adding a new class for CSS selectors $i = 1; foreach ($primary_links as $link => $attributes){ // Append the new class to existing classes for each menu item $class = $attributes['attributes']['class'] . " item-$i"; // Add revised classes back to the primary links temp variable $primary_links[$link]['attributes']['class'] = $class; $link['title'] = '<span class="hide">' . check_plain($link['title']) . '</span>'; $i++; } // end the foreach loop // reset the variable to contain the new markup $vars['primary_links'] = $primary_links; } I've been trying to use the menu_tree() function to no avail, for example: function cti_flex_preprocess_page(&$vars, $hook) { // Make a shortcut for the primary links variables $primary_links = $vars['primary_links']; // Loop thru the menu, adding a new class for CSS selectors $i = 1; foreach ($primary_links as $link => $attributes){ // Append the new class to existing classes for each menu item $class = $attributes['attributes']['class'] . " item-$i"; // Add revised classes back to the primary links temp variable $primary_links[$link]['attributes']['class'] = $class; $link['title'] = '<span class="hide">' . check_plain($link['title']) . '</span>'; $i++; } // end the foreach loop // reset the variable to contain the new markup $vars['primary_links_tree'] = menu_tree(variable_get('menu_primary_links_source', '$primary_links')); } Any ideas would be greatly appreciated.

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• how to use expressons as function parameters in powershell

  - by rmeador

  This is a very simple task in every language I have ever used, but I can't seem to figure it out in PowerShell. An example of what I'm talking about in C: abs(x + y) The expression x + y is evaluated, and the result passed to abs as the parameter... how do I do that in PowerShell? The only way I have figured out so far is to create a temporary variable to store the result of the expression, and pass that. PowerShell seems to have very strange grammar and parsing rules that are constantly catching me by surprise, just like this situation. Does anyone know of documentation or a tutorial that explains the basic underlying theory of the language? I can't believe these are all special cases, there must be some rhyme or reason that no tutorial I have yet read explains. And yes, I've read this question, and all of those tutorials are awful. I've pretty much been relegated to learning from existing code.

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• Run PHP class from JavaScript

  - by jarus

  I need to fire a php class from a javascript function. code: <input type="button" name="Submit" value="Submit" class="opinionbox" onclick="verifyControl('<?=$control_no?>')"/> function verifyControl(rNo) { Cont_no=document.getElementById("ContNo").value; if(rNo==Cont_no) { frames['frame1'].print(); showPage('payment'); } else if(rNo!=Cont_no) { alert("invalid control no"); } } i need to run the code $data = $obj_com -> getSelectedData('tbl', 'control_no', $contno); $control_no = $contno; $obj_com -> recordPay('tbl',$contno); inside the verifyControl() how can I do this?

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• F# Higher-order property accessors

  - by Nathan Sanders

  I just upgraded my prototyping tuple to a record. Someday it may become a real class. In the meantime, I want to translate code like this: type Example = int * int let examples = [(1,2); (3,4); (5,6)] let field1s = Seq.map (fst >> printfn "%d") examples to this: type Example = { Field1 : int Field2 : int Description : string } let examples = [{Field1 = 1; Field2 = 2; Description = "foo"} {Field1 = 3; Field2 = 4; Description = "bar"} {Field1 = 5; Field2 = 6; Description = "baz"}] let field1s = Seq.map Description examples The problem is that I expected to get a function Description : Example -> string when I declared the Example record, but I don't. I've poked around a little and tried properties on classes, but that doesn't work either. Am I just missing something in the documentation or will I have to write higher-order accessors manually? (That's the workaround I'm using now.)

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• Treat a void function as a value

  - by Brendan Long

  I'm writing some terrible, terrible code, and I need a way to put a free() in the middle of a statement. The actual code is: int main(){ return printf("%s", isPalindrome(fgets(malloc(1000), 1000, stdin))?"Yes!\n":"No!\n") >= 0; // leak 1000 bytes of memory } I was using alloca(), but I can't be sure that will actually work on my target computer. My problem is that free returns void, so my code has this error message: error: void value not ignored as it ought to be The obvious idea I had was: int myfree(char *p){ free(p); return 0; } Which is nice in that it makes the code even more unreadable, but I'd prefer not to add another function. I also briefly tried treating free() as a function pointer, but I don't know if that would work, and I don't know enough about C to do it properly. Note: I know this is a terrible idea. Don't try this at home kids.

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• How do I introduce row names to a function in R

  - by Tahnoon Pasha

  Hi I have a utility function I've put together to insert rows into a dataframe below. If I was writing out the formula by hand I would put something like newframe=rbind(oldframe[1:rownum,],row_to_insert=row_to_insert,oldframe[(rownum+1:nrow(oldframe),] to name row_to_insert. Could someone tell me how to do this in a function? Thanks insertrows=function (x, y, rownum) { newframe = rbind(y[1:rownum, ], x, y[(rownum + 1):nrow(y), ]) return(data.frame(newframe)) } MWE of some underlying data added below financials=data.frame(sales=c(100,150,200,250),some.direct.costs=c(25,30,35,40),other.direct.costs=c(15,25,25,35),indirect.costs=c(40,45,45,50)) oldframe=t(financials) colnames(oldframe)=make.names(seq(2000,2003,1)) total.direct.costs=oldframe['some.direct.costs',]+oldframe['other.direct.costs',] newframe=total.direct.costs n=rownum=3 oldframe=insertrows(total.direct.costs=newframe,oldframe,n)

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• Fatal error with Custom Magento Module on one server but not the other

  - by Jack

  Hi, I am creating my own custom module in Magento and during testing on a Litespeed server (PHP v5.2.14) I am getting a Fatal Error: Call to a member function batch() on a non-object in ../../../BatchController.php on line 25 that was not appearing during testing on another linux server and a wamp server (PHP v5.2.11). This one has stumped me. I am guessing it has something to do with the server configuration rather than the code itself. But i am just guessing. I was hoping someone here could tell me. The only real major difference I could see, aside from the php versions and environment, is that the server that the error is on is using the Suhosin Patch. But would that be something that could cause this? The line in question is Mage::getModel('mymodule/mymodel')->batch(); which is enclosed in an IF statement. batch() is a public function located in my model file. If you need more code let me know. Thanks!

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• What's wrong with this function?

  - by ct2k7

  Hello, I'm using this function to determine whether my application should be online or offline: function online() { if ($online == "0") { if($_SESSION['exp_user']['userlevel'] != "1") { include("error/offline.php"); exit(); } } } However, with the data value set to 0 in the database, and $online does = '0', why is error/offline.php not included for those whoose user level is not 1? Thanks :)

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• Should I make sure arguments aren't null before using them in a function.

  - by Nathan W

  The title may not really explain what I'm really trying to get at, couldn't really think of a way to describe what I mean. I was wondering if it is good practice to check the arguments that a function accepts for nulls or empty before using them. I have this function which just wraps some hash creation like so. Public Shared Function GenerateHash(ByVal FilePath As IO.FileInfo) As String If (FilePath Is Nothing) Then Throw New ArgumentNullException("FilePath") End If Dim _sha As New Security.Cryptography.MD5CryptoServiceProvider Dim _Hash = Convert.ToBase64String(_sha.ComputeHash(New IO.FileStream(FilePath.FullName, IO.FileMode.Open, IO.FileAccess.Read))) Return _Hash End Function As you can see I just takes a IO.Fileinfo as an argument, at the start of the function I am checking to make sure that it is not nothing. I'm wondering is this good practice or should I just let it get to the actual hasher and then throw the exception because it is null.? Thanks.

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• How do I select a fixed number of rows for each group?

  - by Maiasaura

  Here is some example data in a mysql table a b distance 15 44 250 94 31 250 30 41 250 6 1 250 95 18 250 72 84 500 14 23 500 55 24 500 95 8 500 59 25 500 40 73 500 65 85 500 32 50 500 31 39 500 22 25 500 37 11 750 98 39 750 15 57 750 9 22 750 14 44 750 69 22 750 62 50 750 89 35 750 67 65 750 74 37 750 52 36 750 66 53 750 82 74 1000 79 22 1000 98 41 1000 How do I query this table such that I get 2 rows per distance selected at random? A successful query will produce something like a b distance 30 41 250 95 18 250 59 25 500 65 85 500 15 57 750 89 35 750 79 22 1000 98 41 1000

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• Stored procedure with output parameters vs. table-valued function?

  - by abatishchev

  Which approach is better to use if I need a member (sp or func) returning 2 parameters: CREATE PROCEDURE Test @in INT, @outID INT OUT, @amount DECIMAL OUT AS BEGIN ... END or CREATE FUNCTION Test ( @in INT ) RETURNS @ret TABLE (outID INT, amount DECIMAL) AS BEGIN ... END What are pros and cons of each approach considering that the result will passed to another stored procedure: EXEC Foobar @outID, @outAmount

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• Fetch Max from a date column grouped by a particular field

  - by vamyip

  Hi, I have a table similar to this: LogId RefId Entered ================================== 1 1 2010-12-01 2 1 2010-12-04 3 2 2010-12-01 4 2 2010-12-06 5 3 2010-12-01 6 1 2010-12-10 7 3 2010-12-05 8 4 2010-12-01 Here, LogId is unique; For each RefId, there are multiple entries with timestamp. What I want to extract is LogId for each latest RefId. I tried solutions from this link:http://stackoverflow.com/questions/121387/sql-fetch-the-row-which-has-the-max-value-for-a-column. But, it returns multiple rows with same RefId. Can someone help me with this? Thanks Vamyip

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• Is a function kind of like a static method?

  - by lkm

  I'm a java programmer and am trying to understand the difference between a method (java methods) and a function (such as in c++). I used to think that they are the same, just different naming conventions for different programming languages. But now that I know they are not, I am having trouble understanding the difference. I know that a method relates to an instance of a class and has access to class data (member variables), while a function does not (?). So is a function kind of like a static method? See here for explanations I read which led me to think this.

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• Inline function and calling cost in C

  - by Eonil

  I'm making a vector/matrix library. (GCC, ARM NEON, iPhone) typedef struct{ float v[4]; } Vector; typedef struct{ Vector v[4]; } Matrix; I passed struct data as pointer to avoid performance degrade from data copying when calling function. So I thought designed function like this: void makeTranslation(const Vector* factor, Matrix* restrict result); But, if function is inline, is there any reason to pass values as pointer for performance? Do those variables copied too? How about register and caches? inline Matrix makeTranslation(Vector factor) __attribute__ ((always_inline)); How do you think about calling costs of each cases?

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• How can I include utility functions from another file into a Sproutcore unit test file?

  - by Lauri

  Lets say I have a few utility functions in file tests/utils/functions.js. I would like to use these functions from several unit test files. However, I'm not able to use them as the Sproutcore build system does not include any external files into the html page used to run the unit tests. Only application code and the code from the unit tests to be run are included. So is it possible to somehow include Javascript files to be used in unit test files in Sproutcore? I could add the functions.js file into some other directory inside my application to be able to use them. However, this is not what I want to do as the utility functions are useless in final production build and would only make my application larger.

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• Why pass by const reference instead of by value?

  - by Maulrus

  From what I understand: when you pass by value, the function makes a local copy of the passed argument and uses that; when the function ends, it goes out of scope. When you pass by const reference, the function uses a reference to the passed argument that can't be modified. I don't understand, however, why one would choose one over the other, except in a situation where an argument needs to be modified and returned. If you had a void function where nothing is getting returned, why choose one over the other?

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• SQL aggregation query, grouping by entries in junction table

  - by cm007

  I have TableA in a many-to-many relationship with TableC via TableB. That is, TableA TableB TableC id | val fkeyA | fkeyC id | data I wish the do select sum(val) on TableA, grouping by the relationship(s) to TableC. Every entry in TableA has at least one relationship with TableC. For example, TableA 1 | 25 2 | 30 3 | 50 TableB 1 | 1 1 | 2 2 | 1 2 | 2 2 | 3 3 | 1 3 | 2 should output 75 30 since rows 1 and 3 in Table have the same relationships to TableC, but row 2 in TableA has a different relationship to TableC. How can I write a SQL query for this?

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• JSP Problem ussing implicit object (session) in a function

  - by user234666

  Can the object of type HttpSession called session be accessed from a function? In a simple jsp page I have a function(see below) defined in the header of the page, and set to an onclick handle of for a button. When I press this button, I'll never see the second alert message. If I do something in the body of the page (like Session ID: <%= session.getId() % ) I have no trouble accessing it. What newbie mistake am I making? function doTest() { alert('Preforming test 122333232'); String sessionId = session.getId(); alert('After access'); if(sessionId == null) { alert('session id is null?'); } Thanks

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• c++ global operator not playing well with template class

  - by John

  ok, i found some similar posts on stackoverflow, but I couldn't find any that pertained to my exact situation and I was confused with some of the answers given. Ok, so here is my problem: I have a template matrix class as follows: template <typename T, size_t ROWS, size_t COLS> class Matrix { public: template<typename, size_t, size_t> friend class Matrix; Matrix( T init = T() ) : _matrix(ROWS, vector<T>(COLS, init)) { /*for( int i = 0; i < ROWS; i++ ) { _matrix[i] = new vector<T>( COLS, init ); }*/ } Matrix<T, ROWS, COLS> & operator+=( const T & value ) { for( vector<T>::size_type i = 0; i < this->_matrix.size(); i++ ) { for( vector<T>::size_type j = 0; j < this->_matrix[i].size(); j++ ) { this->_matrix[i][j] += value; } } return *this; } private: vector< vector<T> > _matrix; }; and I have the following global function template: template<typename T, size_t ROWS, size_t COLS> Matrix<T, ROWS, COLS> operator+( const Matrix<T, ROWS, COLS> & lhs, const Matrix<T, ROWS, COLS> & rhs ) { Matrix<T, ROWS, COLS> returnValue = lhs; return returnValue += lhs; } To me, this seems to be right. However, when I try to compile the code, I get the following error (thrown from the operator+ function): binary '+=' : no operator found which takes a right-hand operand of type 'const matrix::Matrix<T,ROWS,COLS>' (or there is no acceptable conversion) I can't figure out what to make of this. Any help if greatly appreciated!

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• How to find the formula of best case and worst case of my algorithm?

  - by rachel7660

  I was given a task. Write an algorithm so that, the input of 2 lists of data, will have at least one in common. So, this is my algorithm: (I write the code in php) $arrayA = array('5', '6', '1', '2', '7'); $arrayB = array('9', '2', '1', '8', '3'); $arrayC = array(); foreach($arrayA as $val){ if(in_array($val, $arrayB)){ array_push($arrayC, $val); } } Thats my own algo, not sure if its a good one. So, based on my algorithm, how to find the formula of best case and worst case (big O)? Note: Please do let me know, if my algorithm is wrong. My goal is " input of 2 lists of data, will have at least one in common."

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• MySQL - how to retrieve columns in same row as the values returned by min/mx

  - by Gala101

  I couldn't frame the Question's title properly.. Suppose a table of weekly movie Earnings as below, MovieName MovieGross WeekofYear Year So how do I get the names of top grossers for each week of this year If I do select MovieName , Max(MovieGross) , WeekofYear from earnings where year = 2010 group by WeekofYear; Then obviously query wont run, select Max(MovieName) , Max(MovieGross) , WeekofYear from earnings where year = 2010 group by WeekofYear; would just give movies starting with lowest alphabet Is using group-concat and then substring-index the only option here? select substring_index(group_concat(MovieName order by MovieGross desc),',',1), Max(MovieGross) , WeekofYear from earnings where year = 2010 group by WeekofYear ; Seems clumsy.. Is there any better way of acieveing this?

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• Passing a pointer to a function that doesn't match the requirements of the formal parameter

  - by Andreas Grech

  int valid (int x, int y) { return x + y; } int invalid (int x) { return x; } int func (int *f (int, int), int x, int y) { //f is a pointer to a function taking 2 ints and returning an int return f(x, y); } int main () { int val = func(valid, 1, 2), inval = func(invalid, 1, 2); // <- 'invalid' does not match the contract printf("Valid: %d\n", val); printf("Invalid: %d\n", inval); /* Output: * Valid: 3 * Invalid: 1 */ } At the line inval = func(invalid, 1, 2);, why am I not getting a compiler error? If func expects a pointer to a function taking 2 ints and I pass a pointer to a function that takes a single int, why isn't the compiler complaining? Also, since this is happening, what happens to the second parameter y in the invalid function?

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• C newbie malloc question

  - by roufamatic

  Why doesn't this print 5? void writeValue(int* value) { value = malloc(sizeof(int)); *value = 5; } int main(int argc, char * argv) { int* value = NULL; writeValue(value); printf("value = %d\n", *value); // error trying to access 0x00000000 } and how can I modify this so it would work while still using a pointer as an argument to writeValue?

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