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  • SQLAuthority News – Download Whitepaper – Understanding and Controlling Parallel Query Processing in SQL Server

    - by pinaldave
    My recently article SQL SERVER – Reducing CXPACKET Wait Stats for High Transactional Database has received many good comments regarding MAXDOP 1 and MAXDOP 0. I really enjoyed reading the comments as the comments are received from industry leaders and gurus. I was further researching on the subject and I end up on following white paper written by Microsoft. Understanding and Controlling Parallel Query Processing in SQL Server Data warehousing and general reporting applications tend to be CPU intensive because they need to read and process a large number of rows. To facilitate quick data processing for queries that touch a large amount of data, Microsoft SQL Server exploits the power of multiple logical processors to provide parallel query processing operations such as parallel scans. Through extensive testing, we have learned that, for most large queries that are executed in a parallel fashion, SQL Server can deliver linear or nearly linear response time speedup as the number of logical processors increases. However, some queries in high parallelism scenarios perform suboptimally. There are also some parallelism issues that can occur in a multi-user parallel query workload. This white paper describes parallel performance problems you might encounter when you run such queries and workloads, and it explains why these issues occur. In addition, it presents how data warehouse developers can detect these issues, and how they can work around them or mitigate them. To review the document, please download the Understanding and Controlling Parallel Query Processing in SQL Server Word document. Note: Above abstract has been taken from here. The real question is what does the parallel queries has made life of DBA much simpler or is it looked at with potential issue related to degradation of the performance? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL White Papers, SQLAuthority News, T SQL, Technology

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  • SQL SERVER – Quiz and Video – Introduction to Hierarchical Query using a Recursive CTE

    - by pinaldave
    This blog post is inspired from SQL Queries Joes 2 Pros: SQL Query Techniques For Microsoft SQL Server 2008 – SQL Exam Prep Series 70-433 – Volume 2.[Amazon] | [Flipkart] | [Kindle] | [IndiaPlaza] This is follow up blog post of my earlier blog post on the same subject - SQL SERVER – Introduction to Hierarchical Query using a Recursive CTE – A Primer. In the article we discussed various basics terminology of the CTE. The article further covers following important concepts of common table expression. What is a Common Table Expression (CTE) Building a Recursive CTE Identify the Anchor and Recursive Query Add the Anchor and Recursive query to a CTE Add an expression to track hierarchical level Add a self-referencing INNER JOIN statement Above six are the most important concepts related to CTE and SQL Server.  There are many more things one has to learn but without beginners fundamentals one can’t learn the advanced  concepts. Let us have small quiz and check how many of you get the fundamentals right. Quiz 1) You have an employee table with the following data. EmpID FirstName LastName MgrID 1 David Kennson 11 2 Eric Bender 11 3 Lisa Kendall 4 4 David Lonning 11 5 John Marshbank 4 6 James Newton 3 7 Sally Smith NULL You need to write a recursive CTE that shows the EmpID, FirstName, LastName, MgrID, and employee level. The CEO should be listed at Level 1. All people who work for the CEO will be listed at Level 2. All of the people who work for those people will be listed at Level 3. Which CTE code will achieve this result? WITH EmpList AS (SELECT Boss.EmpID, Boss.FName, Boss.LName, Boss.MgrID, 1 AS Lvl FROM Employee AS Boss WHERE Boss.MgrID IS NULL UNION ALL SELECT E.EmpID, E.FirstName, E.LastName, E.MgrID, EmpList.Lvl + 1 FROM Employee AS E INNER JOIN EmpList ON E.MgrID = EmpList.EmpID) SELECT * FROM EmpList WITH EmpListAS (SELECT EmpID, FirstName, LastName, MgrID, 1 as Lvl FROM Employee WHERE MgrID IS NULL UNION ALL SELECT EmpID, FirstName, LastName, MgrID, 2 as Lvl ) SELECT * FROM BossList WITH EmpList AS (SELECT EmpID, FirstName, LastName, MgrID, 1 as Lvl FROM Employee WHERE MgrID is NOT NULL UNION SELECT EmpID, FirstName, LastName, MgrID, BossList.Lvl + 1 FROM Employee INNER JOIN EmpList BossList ON Employee.MgrID = BossList.EmpID) SELECT * FROM EmpList 2) You have a table named Employee. The EmployeeID of each employee’s manager is in the ManagerID column. You need to write a recursive query that produces a list of employees and their manager. The query must also include the employee’s level in the hierarchy. You write the following code segment: WITH EmployeeList (EmployeeID, FullName, ManagerName, Level) AS ( –PICK ANSWER CODE HERE ) SELECT EmployeeID, FullName, ” AS [ManagerID], 1 AS [Level] FROM Employee WHERE ManagerID IS NULL UNION ALL SELECT emp.EmployeeID, emp.FullName mgr.FullName, 1 + 1 AS [Level] FROM Employee emp JOIN Employee mgr ON emp.ManagerID = mgr.EmployeeId SELECT EmployeeID, FullName, ” AS [ManagerID], 1 AS [Level] FROM Employee WHERE ManagerID IS NULL UNION ALL SELECT emp.EmployeeID, emp.FullName, mgr.FullName, mgr.Level + 1 FROM EmployeeList mgr JOIN Employee emp ON emp.ManagerID = mgr.EmployeeId Now make sure that you write down all the answers on the piece of paper. Watch following video and read earlier article over here. If you want to change the answer you still have chance. Solution 1) 1 2) 2 Now compare let us check the answers and compare your answers to following answers. I am very confident you will get them correct. Available at USA: Amazon India: Flipkart | IndiaPlaza Volume: 1, 2, 3, 4, 5 Please leave your feedback in the comment area for the quiz and video. Did you know all the answers of the quiz? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Relationship with Parallelism with Locks and Query Wait – Question for You

    - by Pinal Dave
    Today, I have one very simple question based on following image. A full disclaimer is that I have no idea why it is like that. I tried to reach out to few of my friends who know a lot about SQL Server but no one has any answer. Here is the question: If you go to server properties and click on Advanced you will see the following screen. Under the Parallelism section if you noticed there are four options: Cost Threshold for Parallelism Locks Max Degree of Parallelism Query Wait I can clearly understand why Cost Threshold for Parallelism and Max Degree of Parallelism belongs to Parallelism but I am not sure why we have two other options Locks and Query Wait belongs to Parallelism section. I can see that the options are ordered alphabetically but I do not understand the reason for locks and query wait to list under Parallelism. Here is the question for you – Why Locks and Query Wait options are listed under Parallelism section in SQL Server Advanced Properties? Please leave a comment with your explanation. I will publish valid answers on this blog with due credit. Reference: Pinal Dave (http://blog.sqlauthority.com)   Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Undocumented Query Plans: Equality Comparisons

    - by Paul White
    The diagram below shows two data sets, with differences highlighted: To find changed rows using TSQL, we might write a query like this: The logic is clear: join rows from the two sets together on the primary key column, and return rows where a change has occurred in one or more data columns.  Unfortunately, this query only finds one of the expected four rows: The problem, of course, is that our query does not correctly handle NULLs.  The ‘not equal to’ operators <> and != do not evaluate...(read more)

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  • How can we remove specific string from string ?

    - by Harikrishna
    I will have a different type of string(string will not have fixed format,they will be different every time) from them I want to remove some specific substring.Like the string can be FUTIDX 26FEB2009 NIFTY 0 FUTSTK ONGC 27 Mar 2008 FUTIDX MINIFTY 30 Jul 2009 FUTIDX NIFTY 27 Aug 2009 NIFTY FUT XP: 29/05/2008 Now I want to Remove the string which starts with FUT how can I do that ?

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  • string.format vs + for string concatenatoin

    - by AMissico
    Which is better in respect to performance and memory utilization? // + Operator oMessage.Subject = "Agreement, # " + sNumber + ", Name: " + sName; // String.Format oMessage.Subject = string.Format("Agreement, # {0}, Name: {1}", sNumber, sName); My preference is memory utilization. The + operator is used throughout the application. String.Format and StringBuilder is rarely use. I want to reduce the amount of memory fragmentation caused by excessive string allocations.

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  • How to compare two structure strings in C++

    - by Arvandor
    Ok, so this week in class we're working with arrays. I've got an assignment that wanted me to create a structure for an employee containing an employee ID, first name, last name, and wages. Then it has me ask users for input for 5 different employees all stored in an array of this structure, then ask them for a search field type, then a search value. Lastly, display all the information for all positive search results. I'm still new, so I'm sure it isn't a terribly elegant program, but what I'm trying to do now is figure out how to compare a user entered string with the string stored in the structure... I'll try to give all the pertinent code below. struct employee { int empid, string firstname, string lastname, float wage }; employee emparray[] = {}; employee value[] = {}; //Code for populating emparray and structure, then determine search field etc. cout << "Enter a search value: "; cin >> value.lastname; for(i = 0; i < 5; i++) { if(strcmp(value.lastname.c_str, emparray[i].lastname.c_str) == 0) { output(); } } Which... I thought would work, but it's giving me the following error.. Error 1 error C3867: 'std::basic_string<_Elem,_Traits,_Alloc>::c_str': function call missing argument list; use '&std::basic_string<_Elem,_Traits,_Alloc>::c_str' to create a pointer to member d:\myfile Any thoughts on what's going on? Is there a way to compare two .name notated strings without totally revamping the program? IF you want to drill me on best practices, please feel free, but also please try to solve my particular problem.

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  • Regarding String manipulation

    - by arav
    I have a String str which can have list of values like below. I want the first letter in the string to be uppercase and if underscore appears in the string then i need to remove it and need to make the letter after it as upper case. The rest all letter i want it to be lower case. "" "abc" "abc_def" "Abc_def_Ghi12_abd" "abc__de" "_" Output: "" "Abc" "AbcDef" "AbcDefGhi12Abd" "AbcDe" ""

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  • How to convert a JSON string to a Map<String, String> with Jackson JSON

    - by Infinity
    This is my first time trying to do something useful with Java.. I'm trying to do something like this but it doesn't work: Map<String, String> propertyMap = new HashMap<String, String>(); propertyMap = JacksonUtils.fromJSON(properties, Map.class); But the IDE says: 'Unchecked assignment Map to Map<String,String>' What's the right way to do this? I'm only using Jackson because that's what is already available in the project, is there a native Java way of converting to/from JSON? In PHP I would simply json_decode($str) and I'd get back an array. I need basically the same thing here. Thanks!

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  • specify query timeout when using toplink essential query hint

    - by yhzs8
    Hi, For glassfish v2, I have searched through the web and I cannot find anyway to specify query timeout when using TopLink essential query hint. We have another option to migrate to EclipseLink but that is not feasible. have tried the solution in http://forums.oracle.com/forums/thread.jspa?threadID=974732&tstart=-1 but it seems the DatabaseQuery which one could set a timeout value is actually for Toplink, not TopLink essential. Do we have some other way to instruct the JDBC driver for this timeout value other than the query hint? I need to do it on query-basis and not system-basis (which is just to change the value of DISTRIBUTED_LOCK_TIMEOUT)

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  • mysql query query

    - by nightcoder1
    basically i need to write a query for mysql, but i have no experience in this and i cant find good tutorials on the old tinternet. i have a table called rels with columns "hosd_id" "linkedhost_id" "text link" and a table called hostlist with columns "id" "hostname" all i am trying to achieve is a query which outputs the "hostname" and "linked_id" when "host_id" is equal to "id" any help or pointers on syntax or code would be helpfull, or even a good mysql query guide

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  • mod_rewrite to redirect URL with query string

    - by meeble
    I've searched all over stackoverflow, but none of the answers seem to be working for this situation. I have a lot of working mod_rewrite rules already in my httpd.conf file. I just recently found that Google had indexed one of my non-rewritten URLs with a query string in it: http://domain.com/?state=arizona I would like to use mod_rewrite to do a 301 redirect to this URL: http://domain.com/arizona The issue is that later on in my rewrite rules, that 2nd URL is being rewritten to pass query variables on to WordPress. It ends up getting rewritten to: http://domain.com/index.php?state=arizona Which is the proper functionality. Everything I have tried so far has either not worked at all or put me in an endless rewrite loop. This is what I have right now, which is getting stuck in a loop: RewriteCond %{QUERY_STRING} state=arizona [NC] RewriteRule .* http://domain.com/arizona [R=301,L] #older rewrite rule that passes query string based on URL: RewriteRule ^([A-Za-z-]+)$ index.php?state=$1 [L] which gives me an endless rewrite loop and takes me to this URL: http://domain.com/arizona?state=arizona I then tried this: RewriteRule .* http://domain.com/arizona? [R=301,L] which got rid of the query string in the URL, but still creates a loop.

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  • Combining two-part SQL query into one query

    - by user332523
    Hello, I have a SQL query that I'm currently solving by doing two queries. I am wondering if there is a way to do it in a single query that makes it more efficient. Consider two tables: Transaction_Entries table and Transactions, each one defined below: Transactions - id - reference_number (varchar) Transaction_Entries - id - account_id - transaction_id (references Transactions table) Notes: There are multiple transaction entries per transaction. Some transactions are related, and will have the same reference_number string. To get all transaction entries for Account X, then I would do SELECT E.*, T.reference_number FROM Transaction_Entries E JOIN Transactions T ON (E.transaction_id=T.id) where E.account_id = X The next part is the hard part. I want to find all related transactions, regardless of the account id. First I make a list of all the unique reference numbers I found in the previous result set. Then for each one, I can query all the transactions that have that reference number. Assume that I hold all the rows from the previous query in PreviousResultSet UniqueReferenceNumbers = GetUniqueReferenceNumbers(PreviousResultSet) // in Java foreach R in UniqueReferenceNumbers // in Java SELECT * FROM Transaction_Entries where transaction_id IN (SELECT * FROM Transactions WHERE reference_number=R Any suggestions how I can put this into a single efficient query?

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  • String Occurance Counting Algorithm

    - by Hellnar
    Hello, I am curious what is the most efficient algorithm (or commonly used) to count the number of occurances of a string in a chunck of text. From what I read, Boyer–Moore string search algorithm is the standard for string search but I am not sure if counting occurance in an efficient way would be same as searching a string. In python this is what I want: text_chunck = "one two three four one five six one" occurance_count(text_chunck, "one") # gives 3. Regards EDIT: It seems like python str.count serves me such method however I am not able to find what algorithm it uses.

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  • C++ String tokenisation from 3D .obj files

    - by Ben
    I'm pretty new to C++ and was looking for a good way to pull the data out of this line. A sample line that I might need to tokenise is f 11/65/11 16/70/16 17/69/17 I have a tokenisation method that splits strings into a vector as delimited by a string which may be useful static void Tokenise(const string& str, vector<string>& tokens, const string& delimiters = " ") The only way I can think of doing it is to tokenise with " " as a delimiter, remove the first item from the resulting vector, then tokenise each part by itself. Is there a good way to do this all in one?

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  • string in c++,question

    - by user189364
    Hi, I created a program in C++ that remove commas (') from a given integer. i.e. 2,00,00 would return 20000. I am not using any new space. Here is the program i created void removeCommas(string& str1,int len) { int j=0; for(int i=0;i<len;i++) { if(str1[i] == ',') continue; else { str1[j] =str1[i]; j++; } } str1[j] = '\0'; } void main() { string str1; getline(cin,str1); int i = str1.length(); removeCommas(str1,i); cout<<"the new string "<<str1<<endl; } Here is the result i get : Input : 2,000,00 String length =8 Output = 200000 0 Length = 8 My question is that why does it show the length has 8 in output and shows the rest of string when i did put a null character. It should show output as 200000 and length has 6.

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  • A simple string array Iteration in C# .NET doesn't work

    - by met.lord
    This is a simple code that should return true or false after comparing each element in a String array with a Session Variable. The thing is that even when the string array named 'plans' gets the right attributes, inside the foreach it keeps iterating only over the first element, so if the Session Variable matches other element different than the first one in the array it never returns true... You could say the problem is right there in the foreach cicle, but I cant see it... I've done this like a hundred times and I can't understand what am I doing wrong... Thank you protected bool ValidatePlans() { bool authorized = false; if (RequiredPlans.Length > 0) { string[] plans = RequiredPlans.Split(','); foreach (string plan in plans) { if (MySessionInfo.Plan == plan) authorized = true; } } return authorized; }

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  • How to check if string contains a string in string array

    - by Abu Hamzah
    edit: the order might change as you can see in the below example, both string have same name but different order.... How would you go after checking to see if the both string array match? the below code returns true but in a reality its should return false since I have extra string array in the _check what i am trying to achieve is to check to see if both string array have same number of strings. string _exists = "Adults,Men,Women,Boys"; string _check = "Men,Women,Boys,Adults,fail"; if (_exists.All(s => _check.Contains(s))) //tried Equal { return true; } else { return false; }

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  • query optimization

    - by Gaurav
    I have a query of the form SELECT uid1,uid2 FROM friend WHERE uid1 IN (SELECT uid2 FROM friend WHERE uid1='.$user_id.') and uid2 IN (SELECT uid2 FROM friend WHERE uid1='.$user_id.') The problem now is that the nested query SELECT uid2 FROM friend WHERE uid1='.$user_id.' returns a very large number of ids(approx. 5000). The table structure of the friend table is uid1(int), uid2(int). This table is used to determine whether two users are linked together as friends. Any workaround? Can I write the query in a different way? Or is there some other way to solve this issue. I'm sure I am not the first person to face such a problem. Any help would be greatly appreciated.

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  • std::string.resize() and std::string.length()

    - by dreamlax
    I'm relatively new to C++ and I'm still getting to grips with the C++ Standard Library. To help transition from C, I want to format a std::string using printf-style formatters. I realise stringstream is a more type-safe approach, but I find myself finding printf-style much easier to read and deal with (at least, for the time being). This is my function: using namespace std; string formatStdString(const string &format, ...) { va_list va; string output; size_t needed; size_t used; va_start(va, format); needed = vsnprintf(&output[0], 0, format.c_str(), va); output.resize(needed + 1); // for null terminator?? used = vsnprintf(&output[0], output.capacity(), format.c_str(), va); // assert(used == needed); va_end(va); return output; } This works, kinda. A few things that I am not sure about are: Do I need to make room for a null terminator, or is this unnecessary? Is capacity() the right function to call here? I keep thinking length() would return 0 since the first character in the string is a '\0'. Occasionally while writing this string's contents to a socket (using its c_str() and length()), I have null bytes popping up on the receiving end, which is causing a bit of grief, but they seem to appear inconsistently. If I don't use this function at all, no null bytes appear.

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  • Linq-To-Sql equivalent for this sql query...

    - by Pandiya Chendur
    I thus far used concatenated Id string like 1,2,3 and updated in my table using this query... if exists( select ClientId from Clients where ClientId IN (SELECT i.items FROM dbo.Splitfn(@Id,',') AS i)) begin update Clients set IsDeleted=1 where ClientId IN (SELECT i.items FROM dbo.Splitfn(@Id,',') AS i) select 'deleted' as message end What is the linq-to-sql equivalent for the above query? Any suggestion...

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  • Remove trailing slash with htaccess but preserve query string

    - by soundseller
    I am using following directives in my htaccess to remove trailing slashs from my uris to prevent duplicate content. However these directives also remove any query string, that might be present. RewriteCond %{HTTP_HOST} ^(www.)?mydomain\com$ [NC] RewriteRule ^(.+)/$ http://www.mydomain.com/$1 [R=301,L] I'd like to know how to remove a potential trailing slash from my URI, but also preserve query strings.

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  • Why this query is so slow?

    - by Silver Light
    This query appears in mysql slow query log: it takes 11 seconds. INSERT INTO record_visits ( record_id, visit_day ) VALUES ( '567', NOW() ); The table has 501043 records and it's structure looks like this: CREATE TABLE IF NOT EXISTS `record_visits` ( `id` int(11) NOT NULL AUTO_INCREMENT, `record_id` int(11) DEFAULT NULL, `visit_day` date DEFAULT NULL, `visit_cnt` bigint(20) DEFAULT '1', PRIMARY KEY (`id`), UNIQUE KEY `record_id_visit_day` (`record_id`,`visit_day`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 ; What could be wrong? Why this INSERT takes so long?

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