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  • Does clustered index on foreign key column increase join performance vs non-clustered ?

    - by alpav
    In many places it's recommended that clustered indexes are better utilized when used to select range of rows using BETWEEN statement. When I select joining by foreign key field in such a way that this clustered index is used, I guess, that clusterization should help too because range of rows is being selected even though they all have same clustered key value and BETWEEN is not used. Considering that I care only about that one select with join and nothing else, am I wrong with my guess ?

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  • simple php Dollar $ evaluation in string questions

    - by Mirage
    I have always been confused that .e,g in php i have sql statement $qry = "select * from table where id = $id"; now can i insert "$" directly inside the quotes or i have to use $qry = "select * from table where id =".$id." "; or $qry = 'select * from table where id = $id'; or $qry = 'select * from table where id = '$id''; Which is correct

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  • Python combinations no repeat by constraint

    - by user2758113
    I have a tuple of tuples (Name, val 1, val 2, Class) tuple = (("Jackson",10,12,"A"), ("Ryan",10,20,"A"), ("Michael",10,12,"B"), ("Andrew",10,20,"B"), ("McKensie",10,12,"C"), ("Alex",10,20,"D")) I need to return all combinations using itertools combinations that do not repeat classes. How can I return combinations that dont repeat classes. For example, the first returned statement would be: tuple0, tuple2, tuple4, tuple5 and so on.

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  • How to skip to next iteration in jQuery.each() util?

    - by Josh
    I'm trying to iterate through an array of elements. jQuery's documentation says: jquery.Each() documentation Returning non-false is the same as a continue statement in a for loop, it will skip immediately to the next iteration. I've tried calling 'return non-false;' and 'non-false;' (sans return) neither of which skip to the next iteration. Instead, they break the loop. What am i missing?

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  • install python modules on shared web hosting

    - by Ali
    I am using a shared hosting environment that will not give me access to the command line. Can I download the python module on my computer, compile it using python setup.py installand then simply upload a .py file to the web host? If yes, where does the install statement place the compiled file?

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  • Control statements in Haskell?

    - by Nathan
    I am just beginning Haskell, but from all the online tutorials I've found I can't seem to find if there is one accepted way to do a conditional control statement. I have seen if-else, guards, and pattern matching, but they all seem to accomplish the same thing. Is there one generally accepted/faster/more efficient way than the rest?

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  • LINQ causing my obfuscator to break

    - by JL
    I have the following LINQ that is causing my obfuscator to break. .Where(f => f.FileName == fileName).OrderByDescending(f => f.Position).FirstOrDefault(); Is there another way I could reword this LINQ statement to test against my obfuscator? I've reported the bug, but it could take 1-2 months to fix, so I need to try recode this LINQ in the meantime.

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  • How do you create a transaction that spans multiple statements in Python with MySQLdb?

    - by Fast Fish
    I know that with an InnoDB table, transactions are autocommit, however I understand that to mean for a single statement? For example, I want to check if a user exists in a table, and then if it doesn't, create it. However there lies a race condition. I believe using a transaction prior to doing the select, will ensure that the table remains untouched until the subsequent insert, and the transaction is committed. How can you do this with MySQLdb and Python?

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  • SQL Server CTE referred in self joins slow

    - by Kharlos Dominguez
    Hello, I have written a table-valued UDF that starts by a CTE to return a subset of the rows from a large table. There are several joins in the CTE. A couple of inner and one left join to other tables, which don't contain a lot of rows. The CTE has a where clause that returns the rows within a date range, in order to return only the rows needed. I'm then referencing this CTE in 4 self left joins, in order to build subtotals using different criterias. The query is quite complex but here is a simplified pseudo-version of it WITH DataCTE as ( SELECT [columns] FROM table INNER JOIN table2 ON [...] INNER JOIN table3 ON [...] LEFT JOIN table3 ON [...] ) SELECT [aggregates_columns of each subset] FROM DataCTE Main LEFT JOIN DataCTE BananasSubset ON [...] AND Product = 'Bananas' AND Quality = 100 LEFT JOIN DataCTE DamagedBananasSubset ON [...] AND Product = 'Bananas' AND Quality < 20 LEFT JOIN DataCTE MangosSubset ON [...] GROUP BY [ I have the feeling that SQL Server gets confused and calls the CTE for each self join, which seems confirmed by looking at the execution plan, although I confess not being an expert at reading those. I would have assumed SQL Server to be smart enough to only perform the data retrieval from the CTE only once, rather than do it several times. I have tried the same approach but rather than using a CTE to get the subset of the data, I used the same select query as in the CTE, but made it output to a temp table instead. The version referring the CTE version takes 40 seconds. The version referring the temp table takes between 1 and 2 seconds. Why isn't SQL Server smart enough to keep the CTE results in memory? I like CTEs, especially in this case as my UDF is a table-valued one, so it allowed me to keep everything in a single statement. To use a temp table, I would need to write a multi-statement table valued UDF, which I find a slightly less elegant solution. Did some of you had this kind of performance issues with CTE, and if so, how did you get them sorted? Thanks, Kharlos

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  • How to insert hyperlink into access database via sql?

    - by CSharperWithJava
    I have a fairly simple MS Access Database that contains some metadata about a bunch of documents and a hyperlink field that links to the document on our network drive. However, when I use a SQL INSERT statement to populate the hyperlink field, the value I give it only becomes the display text, not the actual link. How can I make the value a functional hyperlink? I'd think that the hyperlink data type would actually create hyperlinks. I'm using Access 2002 SP3.

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  • jQuery Checkbox class attribute

    - by mike
    how do you access the class attribute of a in a jQuery selector statement? for example <asp:CheckBox runat="server" ID="cbTest" Text="Cb Test" FieldName="1st Test Check Box" class="toggleBox"/> this: $(':checkbox').toggleAttr("checked", true, false) accesses the checkbox and applies a custom function to the checked attribute but if i want to filter based on a certain class how do i access/filter based on that?

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  • How to add new object to an IList mapped as a one-to-many with NHibernate?

    - by Jørn Schou-Rode
    My model contains a class Section which has an ordered list of Statics that are part of this section. Leaving all the other properties out, the implementation of the model looks like this: public class Section { public virtual int Id { get; private set; } public virtual IList<Static> Statics { get; private set; } } public class Static { public virtual int Id { get; private set; } } In the database, the relationship is implemented as a one-to-many, where the table Static has a foreign key pointing to Section and an integer column Position to store its index position in the list it is part of. The mapping is done in Fluent NHibernate like this: public SectionMap() { Id(x => x.Id); HasMany(x => x.Statics).Cascade.All().LazyLoad() .AsList(x => x.WithColumn("Position")); } public StaticMap() { Id(x => x.Id); References(x => x.Section); } Now I am able to load existing Statics, and I am also able to update the details of those. However, I cannot seem to find a way to add new Statics to a Section, and have this change persisted to the database. I have tried several combinations of: mySection.Statics.Add(myStatic) session.Update(mySection) session.Save(myStatic) but the closest I have gotten (using the first two statements), is to an SQL exception reading: "Cannot insert the value NULL into column 'Position'". Clearly an INSERT is attempted here, but NHibernate does not seem to automatically append the index position to the SQL statement. What am I doing wrong? Am I missing something in my mappings? Do I need to expose the Position column as a property and assign a value to it myself? EDIT: Apparently everything works as expected, if I remove the NOT NULL constraint on the Static.Position column in the database. I guess NHibernate makes the insert and immediatly after updates the row with a Position value. While this is an anwers to the question, I am not sure if it is the best one. I would prefer the Position column to be not nullable, so I still hope there is some way to make NHibernate provide a value for that column directly in the INSERT statement. Thus, the question is still open. Any other solutions?

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  • Should mutex.WaitOne() inside or before the try/finally block.

    - by chillitom
    Hi Guys, I was wondering which of the following was the suggested pattern when using Mutex (or Semaphores or ReadWriteLockSlims etc.). Should the initial lock happen inside or outside of the try statement? Is it unimportant? _mutex.WaitOne() try { // critical code } finally { _mutex.ReleaseMutex(); } or try { _mutex.WaitOne() // critical code } finally { _mutex.ReleaseMutex(); }

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  • MySQL : Selecting alternative field if given field is empty

    - by Kyobul
    Hi, I wonder if is it possible to run mysql command which can select an alternative field if the first given field is empty, on the same table. Example : I have table called "posts" which have "intro" and "content". In the same statement I would like to select as a result "content" if "intro" is empty, but not having both in the result array. Thanks in advance

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  • class foo; in header file

    - by Thomas
    Hi, Is some one able to explain why header files have something like this? class foo; // This here? class bar { bar(); }; Do you need an include statement when using this? Thanks.

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  • SQLite3 Integer Max Value

    - by peterwkc
    Hello to all, what is the maximum value of data type INTEGER in sqlite3 ? How do you store ip address in database ? What is attached ? How to create table which belongs to a specific database using sql ddl? What is this error about ? error while the list of system catalogue : no such table: temp.sqlite_master Unable to execute statement Does sqlite3 text data type supoports unicode? Thanks.

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  • C question on functions

    - by benjamin button
    some times i see that functions are defined as below: read_dir(dir) char *dir; { DIR * dirp; struct dirent *d; /* open directory */ dirp = opendir(dir); ......... so on here what is the importance of the statement char *dir; what is the intension behind declaring the pointer soon after the function name and then starting the function body.

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  • Select...Case VB.NET to C# Equivalent

    - by Alex Essilfie
    I just started using C# and I've got a couple of issues. I hook several controls to one event handler as in the following and I want to perform a slightly different action for each control: Private Sub Button_Click(sender as Object, e as EventArgs) _ Handles button1.Click, Button2.Click 'do a general activity Select CType(sender, Button).Name Case button1.Name 'do something Case button2.Name 'do something else Case Else 'do the defalut action End Select End Sub Is there any way of doing the above select statement in C# without having to use nested ifs?

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  • Release Quickie

    - by Meltemi
    How to succinctly handle this situation. I'm not properly releasing contactDictionary in the if statement... NSNumber *pIDAsNumber; ... NSMutableDictionary *contactDictionary = [NSMutableDictionary dictionaryWithDictionary:[defaults dictionaryForKey:kContactDictionary]]; if (!contactDictionary) { contactDictionary = [[NSMutableDictionary alloc] initWithCapacity:1]; } [contactDictionary setObject:pIDAsNumber forKey:[myClass.personIDAsNumber stringValue]]; [defaults setObject:contactDictionary forKey:kContactDictionary];

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  • SQL simple selection of rows according to their time

    - by iracema78280
    Hello, I have a table with measures and the time this measures have been taken in the following form: MM/DD/YYYY HH:MI:SS AM. I have measures over many days starting at the same time every day.The datas are minute by minute so basically the seconds are always = 0. I want to select only the measures for the first 5 minutes of each day. I would have used the where statement but the condition would only be on the minutes and note the date is there a way to do this? Thanks

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