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• How to create a function with vectors and vertical asymptote using MATLAB

  - by Pedro J Trinidad

  Plot the function f(x) = 1.5x / x-4 for -10 equal or less than X equal or less than 10. Notice that the function have a vertical asymptote at x = 4. Plot the function by creating two vectors for the domain of x. The first vector (call it x1) with elements from -10 to 3.7, and the second vector (calle it x2) with elements from 4.3 to 10. For each of the X vector create a Y vector (call them y1 and y2) with the corresponding values of Y according to the function. To plot the function make two curves in the same plot (y1 vs. x1 and y2 vs. x2).

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• Numeric comparison difficulty in R

  - by Matt Parker

  I'm trying to compare two numbers in R as a part of a if-statement condition: (a-b) >= 0.5 In this particular instance, a = 0.58 and b = 0.08... and yet (a-b) >= 0.5 is false. I'm aware of the dangers of using == for exact number comparisons, and this seems related: (a - b) == 0.5) is false, while all.equal((a - b), 0.5) is true. The only solution I can think of is to have two conditions: (a-b) > 0.5 | all.equal((a-b), 0.5). This works, but is that really the only solution? Should I just swear off of the = family of comparison operators forever?

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• IMB_ibImageFromMemory: unknown fileformat?

  - by Antoni4040

  Here's my add-on: import bpy import os import sys import subprocess import threading class ExportToGIMP(bpy.types.Operator): bl_idname = "uv.exporttogimp" bl_label = "Export to GIMP" def execute(self, context): self.filepath = os.path.join(os.path.dirname(bpy.data.filepath), "Layout") bpy.ops.uv.export_layout(filepath=self.filepath, check_existing=True, export_all=False, modified=False, mode='PNG', size=(1024, 1024), opacity=0.25, tessellated=False) self.files = os.path.dirname(bpy.data.filepath) cmd = " (python-fu-bgsync RUN-NONINTERACTIVE)" subprocess.Popen(['gimp', '-b', cmd]) self.update() return {'FINISHED'}; def update(self): self.thread = threading.Timer(3.0, self.update).start() self.filepath2 = "/home/antoni4040/????afa/Layout1.png" bpy.ops.image.open(filepath=self.filepath2, filter_blender=False, filter_image=True, filter_movie=False, filter_python=False, filter_font=False, filter_sound=False, filter_text=False, filter_btx=False, filter_collada=False, filter_folder=True, filemode=9, relative_path=False) tex = bpy.data.textures.new(name = self.filepath2, type = "IMAGE") def exporttogimp_menu(self, context): self.layout.operator(ExportToGIMP.bl_idname, text="Export To GIMP") bpy.utils.register_class(ExportToGIMP) bpy.types.IMAGE_MT_uvs.append(exporttogimp_menu) But I can't load an image, because I get this: Reached EOF while decoding PNG IMB_ibImageFromMemory: unknown fileformat (/home/antoni4040/????afa/Layout1.png) What is that?

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• cocoa - IF failing for double?

  - by Mike

  I have a set of NSTimeIntervals like this: NSArray *mySet = [NSArray arrayWithObjects: [NSNumber numberWithDouble: time1], // [NSNumber numberWithDouble: time2], [NSNumber numberWithDouble: time3], nil]; // suppose that at this time // time1 = 0.00000 // time2 = 18.3200 // time3 = 21.6500 at some point in my code I want to test if currentTime is greater or equal to one of the times on the array, so I do // currentTime = 18.32 right now for (int i=0; i<[mySet count]; i++) { if (currentTime >= [[mySet objectAtIndex:i] doubleValue]) { NSLog(@"%d...", i); } } The output should be "1...2..." but the output is just "1..." when i = 1, it is comparing 18.32 to 18.32 and failing to recognize that the value is equal or greater than the other? WTF??? How can that be? thanks for any help.

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• Implement functionality in PHP?

  - by Rachel

  How can we Implement Bisect Python functionality in PHP Implement function bisect_left($arr, $item); as a pure-PHP routine to do a binary-bisection search for the position at which to insert $item into $list, maintaining the sort order therein. Assumptions: Assume that $arr is already sorted by whatever comparisons would be yielded by the stock PHP < operator, and that it's indexed on ints. The function should return an int, representing the index within the array at which $item would be inserted to maintain the order of the array. The returned index should be below any elements in $arr equal to $item, i.e., the insertion index should be "to the left" of anything equal to $item. Search routine should not be linear! That is, it should honor the name, and should attempt to find it by iteratively bisecting the list and comparing only around the midpoint.

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• Why does SFINAE not apply to this?

  - by Simon Buchan

  I'm writing some simple point code while trying out Visual Studio 10 (Beta 2), and I've hit this code where I would expect SFINAE to kick in, but it seems not to: template<typename T> struct point { T x, y; point(T x, T y) : x(x), y(y) {} }; template<typename T, typename U> struct op_div { typedef decltype(T() / U()) type; }; template<typename T, typename U> point<typename op_div<T, U>::type> operator/(point<T> const& l, point<U> const& r) { return point<typename op_div<T, U>::type>(l.x / r.x, l.y / r.y); } template<typename T, typename U> point<typename op_div<T, U>::type> operator/(point<T> const& l, U const& r) { return point<typename op_div<T, U>::type>(l.x / r, l.y / r); } int main() { point<int>(0, 1) / point<float>(2, 3); } This gives error C2512: 'point<T>::point' : no appropriate default constructor available Given that it is a beta, I did a quick sanity check with the online comeau compiler, and it agrees with an identical error, so it seems this behavior is correct, but I can't see why. In this case some workarounds are to simply inline the decltype(T() / U()), to give the point class a default constructor, or to use decltype on the full result expression, but I got this error while trying to simplify an error I was getting with a version of op_div that did not require a default constructor*, so I would rather fix my understanding of C++ rather than to just do what works. Thanks! *: the original: template<typename T, typename U> struct op_div { static T t(); static U u(); typedef decltype(t() / u()) type; }; Which gives error C2784: 'point<op_div<T,U>::type> operator /(const point<T> &,const U &)' : could not deduce template argument for 'const point<T> &' from 'int', and also for the point<T> / point<U> overload.

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• Can sizeof return 0 (zero)

  - by TheJuice

  Is it possible for the sizeof operator to ever return 0 (zero) in C or C++?

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• IF Statement has strange behavior

  - by BSchlinker

  I've developed a 'custom' cout, so that I can display text to console and also print it to a log file. This cout class is passed a different integer on initialization, with the integer representing the verbosity level of the message. If the current verbosity level is greater then or equal to the verbosity level of the message, the message should print. The problem is, I have messages printing even when the current verbosity level is too low. I went ahead and debugged it, expecting to find the problem. Instead, I found multiple scenarios where my if statements are not working as expected. The statement if(ilralevel_passed <= ilralevel_set) will sometimes proceed even if ilralevel_set is LESS then ilralevel_passed. You can see this behavior in the following picture (my apologizes for using Twitpic) http://twitpic.com/1xtx4g/full. Notice how ilralevel_set is equal to zero, and ilralevel_passed is equal to one. Yet, the if statement has returned true and is now moving forward to pass the line to cout. I've never seen this type of behavior before and I'm not exactly sure how to proceed debugging it. I'm not able to isolate the behavior either -- it only occurs in certain parts of my program. Any suggestions are appreciated as always. // Here is an example use of the function: // ilra_status << setfill('0') << setw(2) << dispatchtime.tm_sec << endl; // ilra_warning << "Dispatch time (seconds): " << mktime(&dispatchtime) << endl; // Here is the 'custom' cout function: #ifndef ILRA_H_ #define ILRA_H_ // System libraries #include <iostream> #include <ostream> #include <sstream> #include <iomanip> // Definitions #define ilra_talk ilra(__FUNCTION__,0) #define ilra_update ilra(__FUNCTION__,0) #define ilra_error ilra(__FUNCTION__,1) #define ilra_warning ilra(__FUNCTION__,2) #define ilra_status ilra(__FUNCTION__,3) // Statics static int ilralevel_set = 0; static int ilralevel_passed; // Classes class ilra { public: // constructor / destructor ilra(const std::string &funcName, int toset) { ilralevel_passed = toset; } ~ilra(){}; // enable / disable irla functions static void ilra_verbose_level(int toset){ ilralevel_set = toset; } // output template <class T> ilra &operator<<(const T &v) { if(ilralevel_passed <= ilralevel_set) std::cout << v; return *this; } ilra &operator<<(std::ostream&(*f)(std::ostream&)) { if(ilralevel_passed <= ilralevel_set) std::cout << *f; return *this; } }; // end of the class #endif /* ILRA_H_ */

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• Which are your favorite programming language gadgets?

  - by FerranB

  There are some gadgets/features for programming languages that I like a lot because they save a lot of coding or simply because they are magical or nice. Some of my favorites are: C++ increment/decrement operator: my_array[++c]; C++ assign and sum or substract (...): a += b C# yield return: yield return 1; C# foreach: foreach (MyClass x in MyCollection) PLSQL for loop: for c in (select col1, col2 from mytable) PLSQL pipe row: for i in 1..x loop pipe row(i); end loop; Python Array access operator: a[:1] PLSQL ref cursors. Which are yours?

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• How to efficiently SELECT rows from database table based on selected set of values

  - by Chau Chee Yang

  I have a transaction table of 1 million rows. The table has a field name "Code" to keep customer's ID. There are about 10,000 different customer code. I have an GUI interface allow user to render a report from transaction table. User may select arbitrary number of customers for rendering. I use IN operator first and it works for few customers: SELECT * FROM TRANS_TABLE WHERE CODE IN ('...', '...', '...') I quickly run into problem if I select few thousand customers. There is limitation using IN operator. An alternate way is create a temporary table with only one field of CODE, and inject selected customer codes into the temporary table using INSERT statement. I may then using SELECT A.* FROM TRANS_TABLE A INNER JOIN TEMP B ON (A.CODE=B.CODE) This works nice for huge selection. However, there is performance overhead for temporary table creation, INSERT injection and dropping of temporary table. Do you aware of better solution to handle this situation?

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• How do I use modulus for float/double?

  - by ShrimpCrackers

  I'm creating an RPN calculator for a school project. I'm having trouble with the modulus operator. Since we're using the double data type, modulus won't work on floating point numbers. For example, 0.5 % 0.3 should return 0.2 but I'm getting a division by zero exception. The instruction says to use fmod(). I've looked everywhere for fmod(), including javadocs but I can't find it. I'm starting to think it's a method I'm going to have to create? edit: hmm, strange. I just plugged in those numbers again and it seems to be working fine...but just in case. Do I need to watch out using the mod operator in Java when using floating types? I know something like this can't be done in C++ (I think).

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• Referring to this pointer in a static assert?

  - by Tyson Jacobs

  Is it possible to write a static assert referring to the 'this' pointer? I do not have c++11 available, and BOOST_STATIC_ASSERT doesn't work. struct blah { void func() {BOOST_STATIC_ASSERT(sizeof(*this));} }; Produces: error C2355: 'this' : can only be referenced inside non-static member functions error C2027: use of undefined type 'boost::STATIC_ASSERTION_FAILURE' In MSVC 2008. Motivation: #define CLASS_USES_SMALL_POOL() \ void __small_pool_check() {BOOST_STATIC_ASSERT(sizeof(*this) < SMALL_MALLOC_SIZE;} \ void* operator new(size_t) {return SmallMalloc();} \ void operator delete(void* p) {SmallFree(p);}

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• Constructor or Explicit cast

  - by Felan

  In working with Linq to Sql I create a seperate class to ferry data to a web page. To simplify creating these ferry objects I either use a specialized constructor or an explicit conversion operator. I have two questions. First which approach is better from a readibility perspective? Second while the clr code that is generated appeared to be the same to me, are there situations where one would be treated different than the other by the compiler (in lambda's or such). Example code (DatabaseFoo uses specialized constructor and BusinessFoo uses explicit operator): public class DatabaseFoo { private static int idCounter; // just to help with generating data public int Id { get; set; } public string Name { get; set; } public DatabaseFoo() { Id = idCounter++; Name = string.Format("Test{0}", Id); } public DatabaseFoo(BusinessFoo foo) { this.Id = foo.Id; this.Name = foo.Name; } } public class BusinessFoo { public int Id { get; set; } public string Name { get; set; } public static explicit operator BusinessFoo(DatabaseFoo foo) { return FromDatabaseFoo(foo); } public static BusinessFoo FromDatabaseFoo(DatabaseFoo foo) { return new BusinessFoo {Id = foo.Id, Name = foo.Name}; } } public class Program { static void Main(string[] args) { Console.WriteLine("Creating the initial list of DatabaseFoo"); IEnumerable<DatabaseFoo> dafoos = new List<DatabaseFoo>() { new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo()}; foreach(DatabaseFoo dafoo in dafoos) Console.WriteLine(string.Format("{0}\t{1}", dafoo.Id, dafoo.Name)); Console.WriteLine("Casting the list of DatabaseFoo to a list of BusinessFoo"); IEnumerable<BusinessFoo> bufoos = from x in dafoos select (BusinessFoo) x; foreach (BusinessFoo bufoo in bufoos) Console.WriteLine(string.Format("{0}\t{1}", bufoo.Id, bufoo.Name)); Console.WriteLine("Creating a new list of DatabaseFoo by calling the constructor taking BusinessFoo"); IEnumerable<DatabaseFoo> fufoos = from x in bufoos select new DatabaseFoo(x); foreach(DatabaseFoo fufoo in fufoos) Console.WriteLine(string.Format("{0}\t{1}", fufoo.Id, fufoo.Name)); } }

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• REST/ROA Architecture - Send database search/querying/filter/sorting parameters in URL? (>, <, IN, e

  - by DutrowLLC

  I'm building a REST interface to my application using ROA (Resource Oriented Architecture) . I'd like to give the client the ability to specify search parameters in URL. So a client could say "Give me all people who's: "first_name" is equal to "BOB" "age" is greater than "30" sort by "last_name" I was thinking something like: GET /PEOPLE/{query_parameters}/{sort_parameters} ...or perhaps GET /PEOPLE?query=<query_string>&sort=<sort_string> ...but I'm unsure what syntax would be good for specifying in the COLUMN_NAME-OPERATOR-VALUE triplicates. I was thinking perhaps something like: column_name.operator.value So the client could say: GET /PEOPLE?query=first_name.EQUALS.bob&query=age.GREATER_THAN.30&sort=last_name.ASCENDING I really don't want to re-invent the wheel here, are there some accepted ways that this is done? I am using Restlets, I don't know if that makes a difference.

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• How to evaluate a custom math expression in Python

  - by taynaron

  I'm writing a custom dice rolling parser (snicker if you must) in python. Basically, I want to use standard math evaluation but add the 'd' operator: #xdy sum = 0 for each in range(x): sum += randInt(1, y) return sum So that, for example, 1d6+2d6+2d6-72+4d100 = (5)+(1+1)+(6+2)-72+(5+39+38+59) = 84 I was using regex to replace all 'd's with the sum and then using eval, but my regex fell apart when dealing with parentheses on either side. Is there a faster way to go about this than implementing my own recursive parsing? Perhaps adding an operator to eval?

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• Compare and find differences in two tables in Oracle

  - by Ruslan

  Hi! i have 2 tables: account: ID, ACC, AE_CCY, DRCR_IND, AMOUNT, MODULE flex: ID, ACC, AE_CCY, DRCR_IND, AMOUNT, MODULE I want to show differences comparing only by: AE_CCY, DRCR_IND, AMOUNT, MODULE and ACC by first 4 characters Example: ID ACC AE_CCY DRCR_IND AMOUNT MODULE -- --------- ------ -------- ------ ------ 1 734647674 USD D 100 OP and in flex: ID ACC AE_CCY DRCR_IND AMOUNT MODULE -- --------- ------ -------- ------ ------ 1 734647654 USD D 100 OP 2 734665474 USD D 100 OP 9 734611111 USD D 100 OP ID's 2 and 9 should be shown as differences. If I use FULL JOIN I'll get no differences as substr(account.ACC,1,4) = substr(flex.ACC,1,4) are equal and others are equal and MINUS doesn't work because ID's different. Thanks.

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• Search object array for matching possible multiple values using different comparison operators

  - by Sparkles

  I have a function to search an array of objects for a matching value using the eq operator, like so: sub find { my ( $self, %params ) = @_; my @entries = @{ $self->{_entries} }; if ( $params{filename} ) { @entries = grep { $_->filename eq $params{filename} } @entries; } if ( $params{date} ) { @entries = grep { $_->date eq $params{date} } @entries; } if ( $params{title} ) { @entries = grep { $_->title eq $params{title} } @entries; } .... I wanted to also be able to pass in a qr quoted variable to use in the comparison instead but the only way I can think of separating the comparisons is using an if/else block, like so: if (lc ref($params{whatever}) eq 'regexp') { #use =~ } else { #use eq } Is there a shorter way of doing it? Because of reasons beyond my control I'm using Perl 5.8.8 so I can't use the smart match operator. TIA

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• C# Lambda Problem

  - by Chris Klepeis

  Probably something simple, but as I'm new to lambda expressions, the problem evades me: m => m.contactID == contactID && m.primaryAddress == true && (m.addressTypeID == 2 || m.addressTypeID == 3) I tried to use that lambda expression but I receive an invalid operator. Is there a way to simplify this so that it would work? Edit: The equivolent sql query would be: SELECT * FROM Contact WHERE contactID = 3 AND primaryAddress = 1 AND (addressTypeID = 2 OR addressTypeID = 3) I have a repository function defined like so: public E Single(Expression<Func<E, bool>> where) { return objectSet.Single<E>(where); } I'm passing the lambda expression above into this function. Invalid operator error.

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• How can I have a serializable struct that wraps it's self as an int32 implicitly? in C#?

  - by firoso

  Long story short, I have a struct (see below) that contains exactly one field: private int value; I've also implemented implicit conversion operators: public static implicit operator int(Outlet val) { return val.value; } public static implicit operator Outlet(int val) { return new Outlet(val); } I've implemented all of the following : IComparable, IComparable<Cart>, IComparable<int>, IConvertible, IEquatable<Cart>, IEquatable<int>, IFormattable I'm at a point where I really have no clue why, but whenever I serialize this object, I get no value. For instance, with XmlSerialization: <Outlet /> Also, I'm not solely concerned about XmlSerialization, I'm concerned about ALL serialization (binary for instance) How can I ensure that this serializes properly? NOTE: I did this because mapping an int,int dictionary seemed rather poorly typed to me when explicit objects with validation behavior were desired.

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• What are the common programming mistakes in Python?

  - by Paul McGuire

  I was about to tag the recent question in which the OP accidentally shadowed the builtin operator module with his own local operator.py with the "common-mistakes" tag, and I saw that there are a number of interesting questions posted asking for common mistakes to avoid in Java, Ruby, Scala, Clojure, .Net, jQuery, Haskell, SQL, ColdFusion, and so on, but I didn't see any for Python. For the benefit of Python beginners, can we enumerate the common mistakes that we have all committed at one time or another, in the hopes of maybe steering a newbie or two clear of them? (In homage to "The Princess Bride", I call these the Classic Blunders.) If possible, a little supporting explanation on what the problem is, and the generally accepted resolution/workaround, so that the beginning Pythoner doesn't read your answer and say "ok, that's a mistake, how do I fix it?"

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• Why does C# not implement GetHashCode for Collections?

  - by Peterdk

  I am porting something from Java to C#. In Java the hashcode of a ArrayList depends on the items in it. In C# I always get the same hashcode from a List... Why is this? For some of my objects the hashcode needs to be different because the objects in their list property make the objects non-equal. I would expect that a hashcode is always unique for the object's state and only equals another hashcode when the object is equal. Am I wrong?

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• Returning references while using shared_ptrs

  - by Goose Bumper

  Suppose I have a rather large class Matrix, and I've overloaded operator== to check for equality like so: bool operator==(Matrix &a, Matrix &b); Of course I'm passing the Matrix objects by reference because they are so large. Now i have a method Matrix::inverse() that returns a new Matrix object. Now I want to use the inverse directly in a comparison, like so: if (a.inverse()==b) { ... }` The problem is, this means the inverse method needs to return a reference to a Matrix object. Two questions: Since I'm just using that reference in this once comparison, is this a memory leak? What happens if the object-to-be-returned in the inverse() method belongs to a boost::shared_ptr? As soon as the method exits, the shared_ptr is destroyed and the object is no longer valid. Is there a way to return a reference to an object that belongs to a shared_ptr?

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• mysql left outer join

  - by tirso

  hi to all I have two tables employee and timecard, employee table has fields employee_id,firstname,middlename,lastname and timecard table has fields employee_id,time-in,time-out,tc_date_transaction. I want to select all employee records which have the same employee_id with timecard and date is equal with the current date. If there are no records equal with the current date then return also the records of employee even without time-in,timeout and tc_date_transaction. I have query like this SELECT * FROM employee LEFT OUTER JOIN timecard ON employee.employee_id = timecard.employee_id WHERE tc_date_transaction = "17/06/2010"; result should like this: employee_id,firstname, middlename, lastname,time-in,time-out,tc_date_transaction 1,john,t,cruz,08:00,05:00,17/06/2010 2,mary,j,von,null,null,null any help would greatly appreciated Thanks in advance

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• how to run foreach loop with ternary condition

  - by I Like PHP

  i have two foreach loop to display some data, but i want to use a single foreach on basis of database result. means if there is any row returns from database then forach($first as $fk=>$fv) should execute otherwise foreach($other as $ok) should execute. i m unsing below ternary operator which gives parse error $n=$db->numRows($taskData); // databsse results <?php ($n) ? foreach ($first as $fk=>$fv) : foreach ($other as $ok) { ?> <table><tr><td>......some data...</td></tr></table> <?php } ?> please suggest me how to handle such condition via ternary operator or any other idea. Thanks

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• Little Employee/Shift timetable HELP!!!

  - by DAVID

  Morning Guys, I have the following tables: operator(ope_id, ope_name) ope_shift(ope_id, shift_id, shift_date) shift(shift_id, shift_start, shift_end) here is a better view of the data http://latinunit.net/emp_shift.txt here is the screenshot of a select statement to the tables http://img256.imageshack.us/img256/4013/opeshift.jpg im using this code SELECT OPE_ID, COUNT(OPE_ID) AS Total_shifts from operator_shift group by ope_id; to view the current total shifts per operator and it works, BUT if there was 500 more rows it would count them all aswell, THE QUESTION is, anyone has a better way of making my database work, or how can i tell the system that those rows are a whole month, i remember i friend said something about count then devide by 30 but im not sure, what if the month isnt finished? and you want to show the emp with highest shifts to date

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