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  • Why Use !boolean_variable Over boolean_variable == false

    - by ell
    A comment on this question: Calling A Method that returns a boolean value inside a conditional statement says that you should use !boolean instead of boolean == false when testing conditions. Why? To me boolean == false is much more natural in English and is more explicit. I apologise if this is just a matter of style, but I was wondering if there was some other reason for this preference of !boolean?

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  • MySQL CASE Statements in Multi-Aggregated Crosstab Columns

    Inserting additional columns to a crosstab query is less straightforward than adding row data, because SQL naturally groups data by rows. Moreover, the efficacy of the CASE statement within an aggregate function decreases in direct proportion to the complexity of the criteria. Read on to learn more...

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  • MySQL CASE Statements in Multi-Aggregated Crosstab Columns

    Inserting additional columns to a crosstab query is less straightforward than adding row data, because SQL naturally groups data by rows. Moreover, the efficacy of the CASE statement within an aggregate function decreases in direct proportion to the complexity of the criteria. Read on to learn more...

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  • Adding Column to a SQL Server Table

    - by Dinesh Asanka
    Adding a column to a table is  common task for  DBAs. You can add a column to a table which is a nullable column or which has default values. But are these two operations are similar internally and which method is optimal? Let us start this with an example. I created a database and a table using following script: USE master Go --Drop Database if exists IF EXISTS (SELECT 1 FROM SYS.databases WHERE name = 'AddColumn') DROP DATABASE AddColumn --Create the database CREATE DATABASE AddColumn GO USE AddColumn GO --Drop the table if exists IF EXISTS ( SELECT 1 FROM sys.tables WHERE Name = 'ExistingTable') DROP TABLE ExistingTable GO --Create the table CREATE TABLE ExistingTable (ID BIGINT IDENTITY(1,1) PRIMARY KEY CLUSTERED, DateTime1 DATETIME DEFAULT GETDATE(), DateTime2 DATETIME DEFAULT GETDATE(), DateTime3 DATETIME DEFAULT GETDATE(), DateTime4 DATETIME DEFAULT GETDATE(), Gendar CHAR(1) DEFAULT 'M', STATUS1 CHAR(1) DEFAULT 'Y' ) GO -- Insert 100,000 records with defaults records INSERT INTO ExistingTable DEFAULT VALUES GO 100000 Before adding a Column Before adding a column let us look at some of the details of the database. DBCC IND (AddColumn,ExistingTable,1) By running the above query, you will see 637 pages for the created table. Adding a Column You can add a column to the table with following statement. ALTER TABLE ExistingTable Add NewColumn INT NULL Above will add a column with a null value for the existing records. Alternatively you could add a column with default values. ALTER TABLE ExistingTable Add NewColumn INT NOT NULL DEFAULT 1 The above statement will add a column with a 1 value to the existing records. In the below table I measured the performance difference between above two statements. Parameter Nullable Column Default Value CPU 31 702 Duration 129 ms 6653 ms Reads 38 116,397 Writes 6 1329 Row Count 0 100000 If you look at the RowCount parameter, you can clearly see the difference. Though column is added in the first case, none of the rows are affected while in the second case all the rows are updated. That is the reason, why it has taken more duration and CPU to add column with Default value. We can verify this by several methods. Number of Pages The number of data pages can be obtained by using DBCC IND command. Though, this an undocumented dbcc command, many experts are ok to use this command in production. However, since there is no official word from Microsoft, use this “at your own risk”. DBCC IND (AddColumn,ExistingTable,1) Before Adding the Columns 637 Adding a Column with NULL 637 Adding a column with DEFAULT value 1270 This clearly shows that pages are physically modified. Please note, a high value indicated in the Adding a column with DEFAULT value  column is also a result of page splits. Continues…

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  • Use of c89 in GNU software

    - by Federico Culloca
    In GNU coding standard it is said that free software developer should use C89 because C99 is not widespread yet. 1999 Standard C is not widespread yet, so please do not require its features in programs. Reference here. Are they talking about developers knowledge of C99, or about compilers supporting it? Also, is this statement plausible as of today or is it somewhat "obsolete" or at least obsolescent.

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  • Sub-Select to Delimited List in T-SQL

    - by Doug Lampe
    The following transact-SQL statement can be used with Microsoft SQL Server to create a delimited list from a sub-query.  In this case the delimiter is a comma. SELECT Left(item,LEN(item)-1)as delimited_list FROM (     select       CAST       (          (               select original_item + ','               from TABLE             where condition_field = 'value'             for xml path ('')           )   as varchar(max)      ) as item ) as temp

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  • How can I keep current with Python coding style?

    - by vartec
    I've been using Python since version 2.2. I do pick up new language constructs like for example with statement or dictionary/set comprehensions. However, I've realized that even though I'm being consistent with PEP-8, for existing constructs I'm using old style, rather than new style (for example except Exception, e instead of except Exception as e). Is there a resource which would have either most current style guide, or even better a list of changes in Python's coding style?

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  • Meta Tag and Search Engine Ranking

    According to SEO Services India, Meta Tag is a coding statement in Hyper Text Markup Language (HTML). It is the information displayed on the head, which comes after the title tag of a Web site. This ... [Author: John Anthony - Web Design and Development - June 10, 2010]

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  • Have you used the ExecutionValue and ExecValueVariable properties?

    The ExecutionValue execution value property and it’s friend ExecValueVariable are a much undervalued feature of SSIS, and many people I talk to are not even aware of their existence, so I thought I’d try and raise their profile a bit. The ExecutionValue property is defined on the base object Task, so all tasks have it available, but it is up to the task developer to do something useful with it. The basic idea behind it is that it allows the task to return something useful and interesting about what it has performed, in addition to the standard success or failure result. The best example perhaps is the Execute SQL Task which uses the ExecutionValue property to return the number of rows affected by the SQL statement(s). This is a very useful feature, something people often want to capture into a variable, and start using the result set options to do. Unfortunately we cannot read the value of a task property at runtime from within a SSIS package, so the ExecutionValue property on its own is a bit of a let down, but enter the ExecValueVariable and we have the perfect marriage. The ExecValueVariable is another property exposed through the task (TaskHost), which lets us select a SSIS package variable. What happens now is that when the task sets the ExecutionValue, the interesting value is copied into the variable we set on the ExecValueVariable property, and a variable is something we can access and do something with. So put simply if the ExecutionValue property value is of interest, make sure you create yourself a package variable and set the name as the ExecValueVariable. Have  look at the 3 step guide below: 1 Configure your task as normal, for example the Execute SQL Task, which here calls a stored procedure to do some updates. 2 Create variable of a suitable type to match the ExecutionValue, an integer is used to match the result we want to capture, the number of rows. 3 Set the ExecValueVariable for the task, just select the variable we created in step 2. You need to do this in Properties grid for the task (Short-cut key, select the task and press F4) Now when we execute the sample task above, our variable UpdateQueueRowCount will get the number of rows we updated in our Execute SQL Task. I’ve tried to collate a list of tasks that return something useful via the ExecutionValue and ExecValueVariable mechanism, but the documentation isn’t always great. Task ExecutionValue Description Execute SQL Task Returns the number of rows affected by the SQL statement or statements. File System Task Returns the number of successful operations performed by the task. File Watcher Task Returns the full path of the file found Transfer Error Messages Task Returns the number of error messages that have been transferred Transfer Jobs Task Returns the number of jobs that are transferred Transfer Logins Task Returns the number of logins transferred Transfer Master Stored Procedures Task Returns the number of stored procedures transferred Transfer SQL Server Objects Task Returns the number of objects transferred WMI Data Reader Task Returns an object that contains the results of the task. Not exactly clear, but I assume it depends on the WMI query used.

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  • Message during Edit and Continue doesn't give an option to edit.

    - by Michael Freidgeim
    During my Edit and Continue session I received a message --------------------------- Microsoft Visual Studio --------------------------- Modifying a catch handler around an active statement will prevent the debug session from continuing while Edit and Continue is enabled. --------------------------- OK    --------------------------- I would expect that Visual Studio give me option to edit, but stop Edit and Continue or Cancel, but it only disallow edit .

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  • Checking update reason after actual update

    - by KaRo
    Is there a possibility to find out the reason for at least the last automatic update? When the update-window pops up one can click on the entries and find a statement about what bug shall be fixed with a certain package, or more general why it is updated at all. I want to check for this information afterwards to check if a certain bug or functionality is claimed to be fixed already. thx - robert.

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  • The EXCEPT and INTERSECT Operators in SQL Server

    The UNION, EXCEPT and INTERSECT operators of SQL enable you to combine more than one SELECT statement to form a single result set. Rob Sheldon explains all, with plenty of examples. Join SQL Backup’s 35,000+ customers to compress and strengthen your backups "SQL Backup will be a REAL boost to any DBA lucky enough to use it." Jonathan Allen. Download a free trial now.

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  • SQL SERVER – Fix: Error: 147 An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference

    - by pinaldave
    Everybody was beginner once and I always like to get involved in the questions from beginners. There is a big difference between the question from beginner and question from advanced user. I have noticed that if an advanced user gets an error, they usually need just a small hint to resolve the problem. However, when a beginner gets error he sometimes sits on the error for a long time as he/she has no idea about how to solve the problem as well have no idea regarding what is the capability of the product. I recently received a very novice level question. When I received the problem I quickly see how the user was stuck. When I replied him with the solution, he wrote a long email explaining how he was not able to solve the problem. He thanked multiple times in the email. This whole thing inspired me to write this quick blog post. I have modified the user’s question to match the code with AdventureWorks as well simplified so it contains the core content which I wanted to discuss. Problem Statement: Find all the details of SalesOrderHeaders for the latest ShipDate. He comes up with following T-SQL Query: SELECT * FROM [Sales].[SalesOrderHeader] WHERE ShipDate = MAX(ShipDate) GO When he executed above script it gave him following error: Msg 147, Level 15, State 1, Line 3 An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference. He was not able to resolve this problem, even though the solution was given in the query description itself. Due to lack of experience he came up with another version of above query based on the error message. SELECT * FROM [Sales].[SalesOrderHeader] HAVING ShipDate = MAX(ShipDate) GO When he ran above query it produced another error. Msg 8121, Level 16, State 1, Line 3 Column ‘Sales.SalesOrderHeader.ShipDate’ is invalid in the HAVING clause because it is not contained in either an aggregate function or the GROUP BY clause. What he wanted actually was the SalesOrderHeader all the Sales shipped on the last day. Based on the problem statement what the right solution is as following, which does not generate error. SELECT * FROM [Sales].[SalesOrderHeader] WHERE ShipDate = (SELECT MAX(ShipDate) FROM [Sales].[SalesOrderHeader]) Well, that’s it! Very simple. With SQL Server there are always multiple solution to a single problem. Is there any other solution available to the problem stated? Please share in the comment. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Quick Tip - Speed a Slow Restore from the Transaction Log

    - by KKline
    Here's a quick tip for you: During some restore operations on Microsoft SQL Server, the transaction log redo step might be taking an unusually long time. Depending somewhat on the version and edition of SQL Server you've installed, you may be able to increase performance by tinkering with the readahead performance for the redo operations. To do this, you should use the MAXTRANSFERSIZE parameter of the RESTORE statement. For example, if you set MAXTRANSFERSIZE=1048576, it'll use 1MB buffers. If you...(read more)

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  • Algorithms for pairing a rating system to an assignment queue

    - by blunders
    Attempting to research how to allow a group of people to effectively rank a set of objects (each group member will have contributed one object to the group), and then assign each member an object that's not their own based on: Their ratings of the objects, Their objects rating, and The object remaining to be assigned. Idea is to attempt to assign objects to people based on the groups rating of their contribution to the group relative to other member's contribution, the the personal preferences expressed via the ratings. Any suggestions for: Further research, Refining the statement of the problem/solution, or A solution.

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  • How can I test database access methods in Java?

    - by javaStudent
    I want to write a test for a method that accesses a database such as following. public class MyClass{ public String getAddress(Int id){ String query = "Select * from Address where id="+id; //some additional statements resultSet = statement.executeQuery(); return result.getString(ADDRESS); } } How can I test this method? I am using Java.

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  • Checking if %Y exists in current file in VimScript [closed]

    - by Eduan
    Like the title says. I would love to know how, with VimScript, I can do an if statement, that checks if %Y (for statusline) exists in the current file. This is what I have so far: if expand('%:Y') != "" let filetype=extend('%:Y') let filetype+= ",\ " else let filetype="" endif This is, of course, for my statusline, for which I don't want to show the filetype comma and space if the filetype doesn't exist. BTW, this is a direct copy of this StackOverflow question: http://stackoverflow.com/questions/13314264/checking-if-y-exists-in-current-file-in-vimscript

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  • Can I develop games for mobile platforms in C++?

    - by James Bern
    I have a good grasp in C++ and C and have also experience developing AAA game using C++. Now, I'm shamelessly thinking to dive into mobile game development either in iOS or Android. Unfortunately, I don't know objective-C and java and neither have courage to learn it. So, As above mentioned reason, Is there any possibility to do mobile development in C++ without using any single statement of JAVA and Objective-C ?

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  • Quick Tip - Speed a Slow Restore from the Transaction Log

    - by KKline
    Here's a quick tip for you: During some restore operations on Microsoft SQL Server, the transaction log redo step might be taking an unusually long time. Depending somewhat on the version and edition of SQL Server you've installed, you may be able to increase performance by tinkering with the readahead performance for the redo operations. To do this, you should use the MAXTRANSFERSIZE parameter of the RESTORE statement. For example, if you set MAXTRANSFERSIZE=1048576, it'll use 1MB buffers. If you...(read more)

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  • C to C++ Conversion [closed]

    - by Annalyne
    Can someone convert this code to C++, pretty please? :( #include <stdio.h> #include <stdlib.h> #include <time.h> #define WEAPON_ROPE 10 #define WEAPON_REVOLVER 20 #define WEAPON_LEADPIPE 30 #define WEAPON_CANDLESTICK 40 #define WEAPON_KNIFE 50 #define WEAPON_WRENCH 60 #define PEOPLE_MRGREEN 100 #define PEOPLE_MSSCARLET 200 #define PEOPLE_CONLMUSTARD 300 #define PEOPLE_PROFPLUM 400 #define PEOPLE_MISPEACOCK 500 #define PEOPLE_MISWHITE 600 #define PLACE_KITCHEN 1 #define PLACE_HALL 2 #define PLACE_POOLROOM 3 #define PLACE_STUDY 4 #define PLACE_LOUNG 5 #define PLACE_LIBRARY 6 #define PLACE_CONSERVATORY 7 #define PLACE_DINING 8 #define PLACE_BILLIARDS 9 int main() { int die = 0; int players[6][9] = {{0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}; int allCards[] = {WEAPON_ROPE, WEAPON_REVOLVER, WEAPON_LEADPIPE, WEAPON_CANDLESTICK, WEAPON_CANDLESTICK, WEAPON_KNIFE, WEAPON_WRENCH, PEOPLE_MRGREEN, PEOPLE_MSSCARLET, PEOPLE_CONLMUSTARD, PEOPLE_CONLMUSTARD, PEOPLE_PROFPLUM, PEOPLE_MISPEACOCK, PEOPLE_MISWHITE, PLACE_KITCHEN, PLACE_HALL, PLACE_POOLROOM, PLACE_STUDY, PLACE_LOUNG, PLACE_LIBRARY, PLACE_CONSERVATORY, PLACE_DINING, PLACE_BILLIARDS}; int deckSize = 23; // number of cards in allCards array int count; for (count = 0; count < deckSize; ++count) { printf(", %d", allCards[count]); } // End for // These three array's are so you can put a card back, if need be... int weaponCards[] = {WEAPON_ROPE, WEAPON_REVOLVER, WEAPON_LEADPIPE, WEAPON_CANDLESTICK, WEAPON_CANDLESTICK, WEAPON_KNIFE, WEAPON_WRENCH}; int weaponDeckSize = 7; int peopleCards[] = {PEOPLE_MRGREEN, PEOPLE_MSSCARLET, PEOPLE_CONLMUSTARD, PEOPLE_CONLMUSTARD, PEOPLE_PROFPLUM, PEOPLE_MISPEACOCK, PEOPLE_MISWHITE}; int peopleDeckSize = 7; int placeCards[] = {PLACE_KITCHEN, PLACE_HALL, PLACE_POOLROOM, PLACE_STUDY, PLACE_LOUNG, PLACE_LIBRARY, PLACE_CONSERVATORY, PLACE_DINING, PLACE_BILLIARDS}; int placeDeckSize = 9; srand(clock()); // seed rand() using clock() which gives // the current tick your processor is at... int killer[3]; // no need to initialize yet. killer[0-2] will initialize int deckShuffle = rand() % weaponDeckSize; // picks one number out of the deck killer[0] = weaponCards[deckShuffle]; allCards[deckShuffle] = 0; // Card drawn. No longer exists in deck deckShuffle = rand() % peopleDeckSize; // picks another random card out of the deck killer[1] = peopleCards[deckShuffle]; allCards[deckShuffle + weaponDeckSize] = 0; // Card drawn. No longer exists in deck deckShuffle = rand() % placeDeckSize; // randomly picks the last card needed killer[2] = placeCards[deckShuffle]; allCards[deckShuffle + weaponDeckSize + peopleDeckSize] = 0; // Card drawn. No longer exists in deck int numberOfCards = 0; printf("CLUE\n"); printf("written by John Schintone\n"); printf("Origonal game delvoped by Hasbro\n"); int numberOfPlayers = 0; while ((numberOfPlayers < 3) || (numberOfPlayers > 6)) { printf("How many players are Going to play :\n"); printf("[number] > "); scanf("%d",&numberOfPlayers); // A very fast if statement which only uses integers/char's switch(numberOfPlayers) { case 6: { numberOfCards = 3; } break; case 5: { numberOfCards = 4; } break; case 4: { numberOfCards = 5; } break; case 3: { numberOfCards = 6; } break; default: { printf("You must enter a number between 3 and 6...\n"); } // End default } // End switch } // End while int index1, index2; // Note: ++index1; is faster than index1++; and will almost always // produce better code (index1++ happens after this statement line. // ++index1 increments index1 before this statement line) for (index1 = 0; index1 < numberOfPlayers; ++index1) { printf("Player %d", index1); for (index2 = 0; index2 < numberOfCards; ++index2) { // Remember that allCards[deckShuffle] == 0 because we removed that // card ages ago... works out well, just don't forget you did that : ) while (allCards[deckShuffle] == 0) { deckShuffle = rand() % deckSize; } // End while players[index1][index2] = allCards[deckShuffle]; allCards[deckShuffle] = 0; // Card removed for after loop... printf(", %d", players[index1][index2]); switch(players[index1][index2]) { case WEAPON_ROPE: { } break; // Add more... case PEOPLE_MRGREEN: { } break; // Add more... case PLACE_KITCHEN: { } break; // Add more... default: { printf("Program has caught player %d cheating...", index1); } // End default } // End switch } // End for printf("\n"); } // End for printf("The killer is %d, with the %d, and in the %d \n\n", killer[0], killer[1], killer[2]); printf("Type h for this help... \n"); printf("Type e to escape... \n"); printf("Type r to roll the die... \n"); char command = '\0'; // \0 represents zero, or the null character while (command != 'e') { printf("[one character] > "); scanf("%c", &command); if (command == 'r') { die = rand() % 6 + 1; printf("Your number is: %d \n", die); } // end while if (command == 'h') { printf("Type h for this help... \n"); printf("Type e to escape... \n"); printf("Type r to roll the die... \n"); } // End if printf("\n"); } // End while return(0); // Success. Program worked ok } // End main() Function

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