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  • SQL Server - how to determine if indexes aren't being used?

    - by rwmnau
    I have a high-demand transactional database that I think is over-indexed. Originally, it didn't have any indexes at all, so adding some for common processes made a huge difference. However, over time, we've created indexes to speed up individual queries, and some of the most popular tables have 10-15 different indexes on them, and in some cases, the indexes are only slightly different from each other, or are the same columns in a different order. Is there a straightforward way to watch database activity and tell if any indexes are not hit anymore, or what their usage percentage is? I'm concerned that indexes were created to speed up either a single daily/weekly query, or even a query that's not being run anymore, but the index still has to be kept up to date every time the data changes. In the case of the high-traffic tables, that's a dozen times/second, and I want to eliminate indexes that are weighing down data updates while providing only marginal improvement.

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  • sql: how to use count for a particular column ,(or) to count a particular column by its field name

    - by Aravintha Bashyam
    in my query i need a to count a particular column by its field name, SELECT C.INC_COUNT, MIN_X, MIN_Y, MAX_X, MAX_Y, B.STATE_ABBR, B.STATE_NAME, B.LATITUDE, B.LONGITUDE, A.STATE, GEO_ID, concat(A.LSAD_TRANS,' ' , A.NAME) DIST_NAME, A.LSAD, GeometryType(SHAPE) GEO_TYPE, AsText(SHAPE) GEOM from SHAPE_LAYERS A join SHAPE_LAYER_STATE_DESC B on ( A.state = B.state) left outer join INC_DIST_SUMMARY_ALL C on (C.SHAPE_GEO_ID = A. GEO_ID) here i have to count by B.STATE_NAME ,C.INC_COUNT if exmple the field name nevada means i have to get all neveda value count and the C.INC_COUNT.

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  • PHP, better to set the variable before if or use if/else?

    - by DssTrainer
    So a simple one that I just never could find a straight answer on. What is better (performance or otherwise): $var = false; If ($a == $b) { $var = true; } or If ($a == $b) { $var = true; } else { $var = false; } I've heard arguments for both ways. I find the first cleaner to ensure I have it set, and a little less code too. The pro being that you may only need to set it once without conditional. But the con being that if the argument is true, it gets set twice. I am assuming the second way is probably best practice

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  • How many SQL queries per HTTP request is optimal?

    - by Chris Kooken
    I know the answer to this question for the most part is "It Depends", however I wanted to see if anyone had some pointers. We execute queries each request in ASP.NET MVC. Each request we need to get user rights information, and Various data for the Views that we are displaying. How many is too much, I know I should be conscious to the number of queries i am executing. I would assume if they are small queries and optimized out, half-a-dozen should be okay? Am I right? What do you think?

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  • Rewriting a statement using LINQ(C#)

    - by Thinking
    Is it possible to write the folowing using lambda(C#) private static void GetRecordList(List<CustomerInfo> lstCustinfo) { for (int i = 1; i <= 5; i++) { if (i % 2 == 0) lstCustinfo.Add(new CustomerInfo { CountryCode = "USA", CustomerAddress = "US Address" + i.ToString(), CustomerName = "US Customer Name" + i.ToString(), ForeignAmount = i * 50 }); else lstCustinfo.Add(new CustomerInfo { CountryCode = "UK", CustomerAddress = "UK Address" + i.ToString(), CustomerName = "UK Customer Name" + i.ToString(), ForeignAmount = i * 80 }); } }

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  • Unexpected '{' with IF statement

    - by user1926208
    this is my code to move all the files in a directory to another directory which are 1 hour old or more. <?php $srcDir = 'code'; $destDir = 'code/old'; if (file_exists($destDir)) { if (is_dir($destDir)) { if (is_writable($destDir)) { if ($handle = opendir($srcDir)) { while (false !== ($file = readdir($handle))) { if (is_file($srcDir . '/' . $file)) { if(date("U",filectime($srcDir . '/' . $file) >= time() - 3600) { rename($srcDir . '/' . $file, $destDir . '/' . $file); } } } closedir($handle); } else { echo "$srcDir could not be opened.\n"; } } else { echo "$destDir is not writable!\n"; } } else { echo "$destDir is not a directory!\n"; } } else { echo "$destDir does not exist\n"; } ?> and I am getting this error: Parse error: syntax error, unexpected '{' in /home/tcity/public_html/myDir/movefiles.php on line 11

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  • Lambda "if" statement?

    - by AndyC
    I have 2 objects, both of which I want to convert to dictionarys. I use toDictionary<(). The lambda expression for one object to get the key is (i = i.name). For the other, it's (i = i.inner.name). In the second one, i.name doesn't exist. i.inner.name ALWAYS exists if i.name doesn't. Is there a lambda expression I can use to combine these two? Basically to read as: "if i.name exists then set id to i.name, else set id to i.inner.name". Many thanks.

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  • Which is faster: in_array() or a bunch of expressions in PHP?

    - by Darryl Hein
    Is it faster to do the following: if ($var != 'test1' && $var != 'test2' && $var != 'test3' && $var != 'test4') { ... } Or: if (!in_array($var, array('test1', 'test2', 'test3', 'test4') { ... } Is there a number of values at which point it's faster to do one or the other? (In this case, the array used in the second option doesn't alreay exist.)

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  • Why would SQL be very slow when doing updates?

    - by ooo
    Suddenly doing updates into a few tables have gotten 10 times slower than they used to be. What are some good recommendations to determine root cause and optimization? Could it be that indexing certain columns are causing updates to be slow? Any other recommendations? I guess more important than guesses would be help on the process of identifying the root cause or metrics around performance. Is there anything in Fluent NHibernate that you can use to help identify the root cause of performance issues?

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  • DateTime.Now within a statement

    - by jarrett
    In the below thisIsAlwaysTrue should always be true. DateTime d = DateTime.Now; bool thisIsAlwaysTrue = d == d; But does DateTime.Now work in such a way that isThisAlwaysTrue is guaranteed to be true? Or can the clock change between references to the Now property? bool isThisAlwaysTrue = DateTime.Now == DateTime.Now;

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  • which sql query is more efficient: select count(*) or select ... where key>value?

    - by davka
    I need to periodically update a local cache with new additions to some DB table. The table rows contain an auto-increment sequential number (SN) field. The cache keeps this number too, so basically I just need to fetch all rows with SN larger than the highest I already have. SELECT * FROM table where SN > <max_cached_SN> However, the majority of the attempts will bring no data (I just need to make sure that I have an absolutely up-to-date local copy). So I wander if this will be more efficient: count = SELECT count(*) from table; if (count > <cache_size>) // fetch new rows as above I suppose that selecting by an indexed numeric field is quite efficient, so I wander whether using count has benefit. On the other hand, this test/update will be done quite frequently and by many clients, so there is a motivation to optimize it.

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  • C: Convert A ? B : C into if (A) B else C

    - by tur1ng
    I was looking for a tool that can convert C code expressions for the form: a = (A) ? B : C; into the 'default' syntax with if/else statements: if (A) a = B else a = C Does someone know a tool that's capable to do such a transformation? I work with GCC 4.4.2 and create a preprocessed file with -E but do not want such structures in it.

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  • undefined index mode, which is the variable that case statement is looking for

    - by Brad
    receiving error: PHP Notice: Undefined index: mode in /web/ee_web/include/form-modal.php on line 51 line 51 switch($_GET["mode"]) { block of code it is in: switch($_GET["mode"]) { case "login": login_user(); break; case "logout": session_destroy(); print "<p>You are now logged out.</p>"; print "<p><input type=\"submit\" id=\"closeButton\" name=\"closeButton\" value=\"Close\" onclick=\"self.parent.tb_remove(); parent.location.reload(1);\" /></p>"; break; default: login_user(); //print "<p>How'd you end up here?</p>"; break; } The URL for the page is index.php?mode=logout, that is how I am passing the value into mode. Any way I could resolve this error message?

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  • How do I remove database name from SQL Server generated script?

    - by bucha
    Anytime I use 'script table as' - 'Insert To' (or other command), the script generated automatically places the database name in the script. Such as: INSERT INTO [DatabaseName].[dbo].[tblToBeInserted] ... While not a huge problem to just delete it, it has slipped by a few times and the script breaks if run on a different server with a different database name but has the same schema. (Such as running on [DatabaseName.Test]) Is there an option I can change, or can I modify the output in any way to remove this?

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  • MySQLI Prepared Statement Not Binding Properly

    - by Sev
    Any reason why the following code won't work? $dbconnection = db::getInstance(); //this is a singleton db class $stmt = $dbconnection->prepare("SELECT `id` from `table` where `username`=?"); $stmt->bind_param("s", $username); $stmt->execute(); $stmt->bind_result($uid); $stmt->fetch(); echo $uid; The same connection method is used elsewhere, and it works there. The only difference on that other page where it works, is that there are multiple rows fetched, not just one.

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  • Why do I need the isset() function in php?

    - by Chris
    I am trying to understand the difference between this: if (isset($_POST['Submit'])) { //do something } and if ($_POST['Submit']) { //do something } It seems to me that if the $_POST['Submit'] variable is true, then it is set. Why would I need the isset() function in this case?

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  • variable scope in statement blocks

    - by fearofawhackplanet
    for (int i = 0; i < 10; i++) { Foo(); } int i = 10; // error, 'i' already exists ---------------------------------------- for (int i = 0; i < 10; i++) { Foo(); } i = 10; // error, 'i' doesn't exist By my understanding of scope, the first example should be fine. The fact neither of them are allowed seems even more odd. Surely 'i' is either in scope or not. Is there something non-obvious about scope I don't understand which means the compiler genuinely can't resolve this? Or is just a case of nanny-state compilerism?

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  • What is wrong with the below statement(C#3.0 / Lambda)

    - by Newbie
    what is wrong in the below Enumerable.Range(0, objEntityCode.Count - 1).Select(i => { options.Attributes[i] = new EntityCodeKey { EntityCode = objEntityCode[i].EntityCodes , OrganizationCode = Constants.ORGANIZATION_CODE }; }) .ToArray(); Throwing error The type arguments for method 'System.Linq.Enumerable.Select(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly. But this works Enumerable.Range(0, objEntityCode.Count - 1).ToList().ForEach(i => { options.Attributes[i] = new EntityCodeKey { EntityCode = objEntityCode[i].EntityCodes , OrganizationCode = Constants.ORGANIZATION_CODE }; } ); Using C#3.0. Purpose: I am learning LINQ / LAMBDA and trying to do the same program in different way. Thanks.

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  • Invalid Active Record Statement Rails 2.3.16

    - by Ranzit
    I am using rails 2.3.16 ruby 1.8.7 For the following line of code I ma getting error as follows: Code: ForeignScheduledItem.find(:all, :conditions => { :foreign_scheduled_item => { :scheduled_items => { :subscription_id => params[:subscription_id] } } }, :joins => :scheduled_item).each { |i| @subscriptions.push(Subscription.find_by_id(i.subscription_id)) } Error: ActiveRecord::StatementInvalid (ActiveRecord::StatementInvalid): Can u please help in this regard.

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  • Can this statement ever evaluate to FALSE?

    - by BojanG
    I stumbled upon this while doing a review and the author is not available: int n = Convert.ToInt32(text); if (((n > 0) || (n < 0)) || (n == 0)) { return 1; } The code in general looks solid and it's hard for me to believe that the only purpose of this snippet is to confuse reviewers, but I don't see a way for this condition to fail. Am I missing something?

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