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  • So which null equals this null, that null? maybe this null, or is it this null?

    - by GrumpyOldDBA
    Tuning takes many routes and I get into some interesting situations and often make some exciting finds, see http://sqlblogcasts.com/blogs/grumpyolddba/archive/2010/05/17/just-when-you-thought-it-was-safe.aspx for an example. Today I encountered a multitude of Foreign Key constraints on a table, now FKs are often candidates for indexes and as none of the defined keys had an index it required a closer look. I view foreign key constraints as somewhat of a pain, excessive keys can cause excessive related...(read more)

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  • SQL SERVER – Puzzle Involving NULL – Resolve – Error – Operand data type void type is invalid for sum operator

    - by pinaldave
    Today is Monday let us start this week with interesting puzzle. Yesterday I had also posted quick question here: SQL SERVER – T-SQL Scripts to Find Maximum between Two Numbers Run following code: SELECT SUM(data) FROM (SELECT NULL AS DATA) t It will throw following error. Msg 8117, Level 16, State 1, Line 1 Operand data type void type is invalid for sum operator. I can easily fix if I use ISNULL Function as displayed following. SELECT SUM(data) FROM (SELECT ISNULL(NULL,0) AS DATA) t Above script will not throw an error. However, there is one more method how this can be fixed. Can you come up with another method which will not generate error? Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • Java Arrays.equals() returns false for two dimensional arrays.

    - by Achilles
    Hi there, I was just curious to know - why does Arrays.equals(double[][], double[][]) return false? when in fact the arrays have the same number of elements and each element is the same? For example I performed the following test. ` [java] double[][] a, b; int size =5; a=new double[size][size]; b=new double[size][size]; for( int i = 0; i < size; i++ ) for( int j = 0; j < size; j++ ){ a[i][j]=1.0; b[i][j]=1.0; } if(Arrays.equals(a, b)) System.out.println("Equal"); else System.out.println("Not-equal"); [/java] ` Returns false and prints "Not-equal. on the other hand, if I have something like this: [java] double[] a, b; int size =5; a=new double[size]; b=new double[size]; for( int i = 0; i < size; i++ ){ a[i]=1.0; b[i]=1.0; } if(Arrays.equals(a, b)) System.out.println("Equal"); else System.out.println("Not-equal"); } [/java] returns true and prints "Equal". Does the method only work with single dimensions? if so, is there something similar for multi-dimensional arrays in Java?

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  • How to list column headers of a SQL Server table using sp_help perhaps?

    - by Hamish Grubijan
    Hi, I have a few tables with 70-80 columns in them. I would like to populate them with somewhat random data, unless I will not be able to do so due to key violation, etc. The first step would be simply to get the list of all headers. There seem to be two ways: A) Run select * from table_of_interest; in MSFT SQL Server Management Studio 2008. Now, right-click the result and click "Copy With headers". However, I get zero rows back, and when I try to copy nothing + headers, I get: TITLE: Microsoft SQL Server Management Studio ------------------------------ Value cannot be null. Parameter name: data (System.Windows.Forms) ------------------------------ BUTTONS: OK ------------------------------ This looks like a bug ... anyhow ... there is another way. B) I can run sp_help table_of_interest;. However, I end up getting too much back. I get 7 different tables back but I am only interested in the second one. The columns of the second table are: Column_name | Type | Computed | Length | Prec | Scale | Nullable | TrimTrailingBlanks | FixedLenNullInSource | Collation I might be interested in just a Column_name and Type, but maybe other columns. So ... since sp_help probably runs a bunch of queries ... how do I get under the hood? How can I run the second query AND filter down the number of columns that I am interested in? Many Thanks!

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  • How do boost operators work?

    - by FredOverflow
    boost::operators automatically defines operators like + based on manual implementations like += which is very useful. To generate those operators for T, one inherits from boost::operators<T> as shown by the boost example: class MyInt : boost::operators<MyInt> I am familiar with the CRTP pattern, but I fail to see how it works here. Specifically, I am not really inheriting any facilities since the operators aren't members. boost::operators seems to be completely empty, but I'm not very good at reading boost source code. Could anyone explain how this works in detail? Is this mechanism well-known and widely used?

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  • how to handle delete by illegal address

    - by Davit Siradeghyan
    Suppose we have a situation like this. How to handle this problem? How to protect code from crashes? I know about and use boost smart pointers. But what to do if we have this situation. struct Test { int a; int b; int c; }; Test global; int main() { Test *p = new Test; p->a = 1; p->b = 2; p->c = 3; p = &global; delete p; return 0; }

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  • Why is this code invalid in C#?

    - by mmattax
    The following code will not compile: string foo = "bar"; Object o = foo == null ? DBNull.Value : foo; I get: Error 1 Type of conditional expression cannot be determined because there is no implicit conversion between 'System.DBNull' and 'string' To fix this, I must do something like this: string foo = "bar"; Object o = foo == null ? DBNull.Value : (Object)foo; This cast seems pointless as this is certainly legal: string foo = "bar"; Object o = foo == null ? "gork" : foo; It seems to me that when the ternary branches are of different types, the compiler will not autobox the values to the type object...but when they are of the same type then the autoboxing is automatic. In my mind the first statement should be legal... Can anyone describe why the compiler does not allow this and why the designers of C# chose to do this? I believe this is legal in Java...Though I have not verified this. Thanks. EDIT: I am asking for an understanding of why Java and C# handle this differently, what is going on underneath the scenes in C# that make this invalid. I know how to use ternary, and am not looking for a "better way" to code the examples. I understand the rules of ternary in C#, but I want to know WHY... EDIT (Jon Skeet): Removed "autoboxing" tag as no boxing is involved in this question.

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  • Bitwise AND, Bitwise Inclusive OR question, in Java

    - by Dave
    I've a few lines of code within a project, that I can't see the value of... buffer[i] = (currentByte & 0x7F) | (currentByte & 0x80); It reads the filebuffer from a file, stored as bytes, and then transfers then to buffer[i] as shown, but I can't understand what the overall purpose is, any ideas? Thanks

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  • What does "<<" mean in C#?

    - by Simon G
    Hi, Basically the questions in the title. I'm looking at the MVC 2 source code: public enum HttpVerbs { Get = 1 << 0, Post = 1 << 1, Put = 1 << 2, Delete = 1 << 3, Head = 1 << 4 } and I'm just curious as to what "<<" does. Thanks

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  • using LIKE with logical operators

    - by ryanthegecko
    i can't seem to figure out how to combine LIKE with an OR or AND: DELETE * FROM persons WHERE FirstName = 'Abe' AND LastName LIKE '%coln'; Looks like it should owrk to me but I get error 1064 (syntax0 Is there a correct way to do this?

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  • Implementing __concat__

    - by Casebash
    I tried to implement __concat__, but it didn't work >>> class lHolder(): ... def __init__(self,l): ... self.l=l ... def __concat__(self, l2): ... return self.l+l2 ... def __iter__(self): ... return self.l.__iter__() ... >>> lHolder([1])+[2] Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unsupported operand type(s) for +: 'lHolder' and 'list' How can I fix this?

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  • Should I use `!IsGood` or `IsGood == false`?

    - by chills42
    I keep seeing code that does checks like this if (IsGood == false) { DoSomething(); } or this if (IsGood == true) { DoSomething(); } I hate this syntax, and always use the following syntax. if (IsGood) { DoSomething(); } or if (!IsGood) { DoSomething(); } Is there any reason to use '== true' or '== false'? Is it a readability thing? Do people just not understand Boolean variables? Also, is there any performance difference between the two?

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  • SQL searching table fields with LIKE

    - by Tom Gullen
    Given your data stored somewhere in a database: Hello my name is Tom I like dinosaurs to talk about SQL. SQL is amazing. I really like SQL. We want to implement a site search, allowing visitors to enter terms and return relating records. A user might search for: Dinosaurs And the SQL: WHERE articleBody LIKE '%Dinosaurs%' Copes fine with returning the correct set of records. How would we cope however, if a user mispells dinosaurs? IE: Dinosores (Poor sore dino). How can we search allowing for error in spelling? We can associate common misspellings we see in search with the correct spelling, and then search on the original terms + corrected term, but this is time consuming to maintain. Any way programatically?

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  • VB.NET overloading array access?

    - by Wayne Werner
    Hi, Is it possible to overload the array/dict access operators in VB.net? For example, you can state something like: Dim mydict As New Hashtable() mydict.add("Cool guy", "Overloading is dangerous!") mydict("Cool guy") = "Overloading is cool!" And that works just fine. But what I would like to do is be able to say: mydict("Cool guy") = "3" and then have 3 automagically converted to the Integer 3. I mean, sure I can have a private member mydict.coolguy and have setCoolguy() and getCoolguy() methods, but I would prefer to be able to write it the former way if at all possible. Thanks

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  • Index, assignment and increment in one statement behaves differently in C++ and C#. Why?

    - by Ivan Zlatanov
    Why is this example of code behaving differently in c++ and C#. [C++ Example] int arr[2]; int index = 0; arr[index] = ++index; The result of which will be arr[1] = 1; [C# Example] int[] arr = new int[2]; int index = 0; arr[index] = ++index; The result of which will be arr[0] = 1; I find this very strange. Surely there must be some rationale for both languages to implement it differently? I wonder what would C++/CLI output?

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  • Linq like or other construction

    - by Yauhen Kavalenka
    I have DB oracle in my solution. I want to have some results in this query. Query example: select * from doctor where doctor.name like '%IVANOV_A%'; But if i do it at LINQ i cannot get any result. from p in repository.Doctor.Where(x => x.Name.ToLower().Containsname)) select p; Where 'name' is variable of string parameter. Web layout request next string: "Ivanov a" or "A Ivanov" But i suggest for user choose you pattetn for query. How i can to get "patient by name" if name consist of "First name" and "Last name" but user doesn't know your doctor's full name?

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  • MySQL: Which is faster — INSTR or LIKE?

    - by Grekker
    If your goal is to test if a string exists in a MySQL column (of type 'varchar', 'text', 'blob', etc) which of the following is faster / more efficient / better to use, and why? Or, is there some other method that tops either of these? INSTR( columnname, 'mystring' ) > 0 vs columnname LIKE '%mystring%'

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  • c++ how to ? function_x ( new object1 )

    - by ismail marmoush
    Hi i want to do the next instead of MyClass object; function_x (object); i want to function_x ( new object ); so what will be the structure of the MyClass to be able to do that .. if i just compiled it , it gives me a compile time error answer function_x (MyClass() ) New Edit thanks for the quick answers.. i did ask the wrong Question i should have asked how temporary variables created in C++ and the answer

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  • Optimize conditional operators branching in C#

    - by abatishchev
    Hello. I have next code: return this.AllowChooseAny.Value ? radioSpecific.Checked ? UserManager.CurrentUser.IsClient ? txtSubject.Text : subjectDropDownList.SelectedItem.Text : String.Empty : UserManager.CurrentUser.IsClient ? txtSubject.Text : subjectDropDownList.SelectedItem.Text; or in less complex form: return any ? specified ? isClient ? textbox : dropdown : empty : isClient ? textbox : dropdown; or in schematic form: | any / \ specified isClient / \ / \ isClient empty textbox dropdown / \ textbox dropdown Evidently I have a duplicated block on two different levels. Is it possible to optimize this code to probably split them to one? Or something like that..

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