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• SQL Server Master class winner

  - by Testas

   The winner of the SQL Server MasterClass competition courtesy of the UK SQL Server User Group and SQL Server Magazine!    Steve Hindmarsh     There is still time to register for the seminar yourself at:  www.regonline.co.uk/kimtrippsql     More information about the seminar     Where: Radisson Edwardian Heathrow Hotel, London  When: Thursday 17th June 2010  This one-day MasterClass will focus on many of the top issues companies face when implementing and maintaining a SQL Server-based solution. In the case where a company has no dedicated DBA, IT managers sometimes struggle to keep the data tier performing well and the data available. This can be especially troublesome when the development team is unfamiliar with the affect application design choices have on database performance. The Microsoft SQL Server MasterClass 2010 is presented by Paul S. Randal and Kimberly L. Tripp, two of the most experienced and respected people in the SQL Server world. Together they have over 30 years combined experience working with SQL Server in the field, and on the SQL Server product team itself. This is a unique opportunity to hear them present at a UK event which will: Debunk many of the ingrained misconceptions around SQL Server's behaviour    Show you disaster recovery techniques critical to preserving your company's life-blood - the data    Explain how a common application design pattern can wreak havoc in the database Walk through the top-10 points to follow around operations and maintenance for a well-performing and available data tier! Please Note: Agenda may be subject to change  Sessions Abstracts  KEYNOTE: Bridging the Gap Between Development and Production    Applications are commonly developed with little regard for how design choices will affect performance in production. This is often because developers don't realize the implications of their design on how SQL Server will be able to handle a high workload (e.g. blocking, fragmentation) and/or because there's no full-time trained DBA that can recognize production problems and help educate developers. The keynote sets the stage for the rest of the day. Discussing some of the issues that can arise, explaining how some can be avoided and highlighting some of the features in SQL 2008 that can help developers and DBAs make better use of SQL Server, and troubleshoot when things go wrong.   SESSION ONE: SQL Server Mythbusters  It's amazing how many myths and misconceptions have sprung up and persisted over the years about SQL Server - after many years helping people out on forums, newsgroups, and customer engagements, Paul and Kimberly have heard it all. Are there really non-logged operations? Can interrupting shrinks or rebuilds cause corruption? Can you override the server's MAXDOP setting? Will the server always do a table-scan to get a row count? Many myths lead to poor design choices and inappropriate maintenance practices so these are just a few of many, many myths that Paul and Kimberly will debunk in this fast-paced session on how SQL Server operates and should be managed and maintained.   SESSION TWO: Database Recovery Techniques Demo-Fest  Even if a company has a disaster recovery strategy in place, they need to practice to make sure that the plan will work when a disaster does strike. In this fast-paced demo session Paul and Kimberly will repeatedly do nasty things to databases and then show how they are recovered - demonstrating many techniques that can be used in production for disaster recovery. Not for the faint-hearted!   SESSION THREE: GUIDs: Use, Abuse, and How To Move Forward   Since the addition of the GUID (Microsoft’s implementation of the UUID), my life as a consultant and "tuner" has been busy. I’ve seen databases designed with GUID keys run fairly well with small workloads but completely fall over and fail because they just cannot scale. And, I know why GUIDs are chosen - it simplifies the handling of parent/child rows in your batches so you can reduce round-trips or avoid dealing with identity values. And, yes, sometimes it's even for distributed databases and/or security that GUIDs are chosen. I'm not entirely against ever using a GUID but overusing and abusing GUIDs just has to be stopped! Please, please, please let me give you better solutions and explanations on how to deal with your parent/child rows, round-trips and clustering keys!   SESSION 4: Essential Database Maintenance  In this session, Paul and Kimberly will run you through their top-ten database maintenance recommendations, with a lot of tips and tricks along the way. These are distilled from almost 30 years combined experience working with SQL Server customers and are geared towards making your databases more performant, more available, and more easily managed (to save you time!). Everything in this session will be practical and applicable to a wide variety of databases. Topics covered include: backups, shrinks, fragmentation, statistics, and much more! Focus will be on 2005 but we'll explain some of the key differences for 2000 and 2008 as well. Speaker Biographies     Kimberley L. Tripp Paul and Kimberly are a husband-and-wife team who own and run SQLskills.com, a world-renowned SQL Server consulting and training company. They are both SQL Server MVPs and Microsoft Regional Directors, with over 30 years of combined experience on SQL Server. Paul worked on the SQL Server team for nine years in development and management roles, writing many of the DBCC commands, and ultimately with responsibility for core Storage Engine for SQL Server 2008. Paul writes extensively on his blog (SQLskills.com/blogs/Paul) and for TechNet Magazine, for which he is also a Contributing Editor. Kimberly worked on the SQL Server team in the early 1990s as a tester and writer before leaving to found SQLskills and embrace her passion for teaching and consulting. Kimberly has been a staple at worldwide conferences since she first presented at TechEd in 1996, and she blogs at SQLskills.com/blogs/Kimberly. They have written Microsoft whitepapers and books for SQL Server 2000, 2005 and 2008, and are regular, top-rated presenters worldwide on database maintenance, high availability, disaster recovery, performance tuning, and SQL Server internals. Together they teach the SQL MCM certification and throughout Microsoft.In their spare time, they like to find frogfish in remote corners of the world.   Speaker Testimonials  "To call them good trainers is an epic understatement. They know how to deliver technical material in ways that illustrate it well. I had to stop Paul at one point and ask him how long it took to build a particular slide because the animations were so good at conveying a hard-to-describe process." "These are not beginner presenters, and they put an extreme amount of preparation and attention to detail into everything that they do. Completely, utterly professional." "When it comes to the instructors themselves, Kimberly and Paul simply have no equal. Not only are they both ultimate authorities, but they have endless enthusiasm about the material, and spot on delivery. If either ever got tired they never showed it, even after going all day and all week. We witnessed countless demos over the course of the week, some extremely involved, multi-step processes, and I can’t recall one that didn’t go the way it was supposed to." "You might think that with this extreme level of skill comes extreme levels of egotism and lack of patience. Nothing could be further from the truth. ... They simply know how to teach, and are approachable, humble, and patient." "The experience Paul and Kimberly have had with real live customers yields a lot more information and things to watch out for than you'd ever get from documentation alone." “Kimberly, I just wanted to send you an email to let you know how awesome you are! I have applied some of your indexing strategies to our website’s homegrown CMS and we are experiencing a significant performance increase. WOW....amazing tips delivered in an exciting way!  Thanks again” 

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• Android: Filtering a SimpleCursorAdapter ListView

  - by Diego Tori

  Right now, I'm running into issues trying to implement a FilterQueryProvider in my custom SimpleCursorAdapter, since I'm unsure of what to do in the FilterQueryProvider's runQuery function. In other words, since the query that comprises my ListView basically gets the rowID, name, and a third column from my databases's table, I want to be able to filter the cursor based on the partial value of the name column. However, I am uncertain of whether I can do this directly from runQuery without expanding my DB class since I want to filter the existing cursor, or will I have to create a new query function in my DB class that partially searches my name column, and if so, how would I go about creating the query statement while using the CharSequence constraint argument in runQuery? I am also concerned about the performance issues associated with trying to run multiple queries based on partial text since the DB table in question has about 1300-1400 rows. In other words, would I run into a bottleneck trying to filter the cursor?

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• Slow select when inserting large amounts of data (MYSQL)

  - by siannopollo

  I have a process that imports a lot of data (950k rows) using inserts that insert 500 rows at a time. The process generally takes about 12 hours, which isn't too bad. Normally doing a query on the table is pretty quick (under 1 second) as I've put (what I think to be) the proper indexes in place. The problem I'm having is trying to run a query when the import process is running. It is making the query take almost 2 minutes! What can I do to make these two things not compete for resources (or whatever)? I've looked into "insert delayed" but not sure I want to change the table to MyISAM. Thanks for any help!

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• PostGres Error When Using Distinct : postgres ERROR: could not identify an ordering operator for ty

  - by CaffeineIV

  ** EDIT ** Nevermind, just needed to take out the parens... I get this error: ERROR: could not identify an ordering operator for type record when trying to use DISTINCT Here's the query: select DISTINCT(g.fielda, g.fieldb, r.type) from fields g LEFT JOIN types r ON g.id = r.id; And the errors: ERROR: could not identify an ordering operator for type record HINT: Use an explicit ordering operator or modify the query. ********** Error ********** ERROR: could not identify an ordering operator for type record SQL state: 42883 Hint: Use an explicit ordering operator or modify the query.

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• The specified type member 'EntityKey' is not supported in LINQ to Entities

  - by user300992

  I have 2 Entities "UserProfile" and "Agent", they are 1-many relationship. I want to do a query to get a list of Agents by giving the userProfileEntityKey. When I run it, I got this "The specified type member 'EntityKey' is not supported in LINQ to Entities" error. public IQueryable<Agent> GetAgentListByUserProfile(EntityKey userProfileEntityKey) { ObjectQuery<Agent> agentObjects = this.DataContext.AgentSet; IQueryable<Agent> resultQuery = (from p in agentObjects where p.UserProfile.EntityKey == userProfileEntityKey select p); return resultQuery; } So, what is the correct way to do this? Do I use p.UserProfile.UserId = UserId ? If that's the case, it's not conceptual anymore. Or should I write object query instead of LINQ query?

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• Add WhereParameters to LinqDataSource in Selecting event

  - by Steven

  I have a repeater using a LinqDataSource as a data source. When a query string is entered, I'd like to filter the results, but ONLY when a query string is entered. If there is no query string, the results should not be filtered, all results should be returned. I'm trying to add a WhereParameter to my LinqDataSource in the Selecting event of the LinqDataSource, but it's not working. Here's my code: protected void ldsImages_Selecting(object sender, LinqDataSourceSelectEventArgs e) { if (Request.QueryString["id"] != null) { e.WhereParameters.Add("ImageTypeID", Request.QueryString["id"]); } }

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• PHP PDO MySQL IN (?,?,?...

  - by nute

  I want to write a MySQL statement like: SELECT * FROM someTable WHERE someId IN (value1, value2, value3, ...) The trick here is that I do not know ahead of time how many values there will be in the IN(). Obviously I know I can generate the query on the go with string manipulations, however since this will run in a loop, I was wondering if I could do it with a PDO PreparedStatement. Something like: $query = $PDO->prepare('SELECT * FROM someTable WHERE someId IN (:idList)'); $query->bindValue(':idList', implode(',', $idArray)); Is that possible?

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• How to group a complex list of objects using LINQ?

  - by Daoming Yang

  I want to select and group the products, and rank them by the number of times they occur. For example, I have an OrderList each of order object has a OrderProductVariantList(OrderLineList), and each of OrderProductVariant object has ProductVariant, and then the ProductVariant object will have a Product object which contains product information. A friend helped me with the following code. It could be compiled, but it did not return any value/result. I used the watch window for the query and it gave me "The name 'query' does not exist in the current context". Can anyone help me? Many thanks. var query = orderList.SelectMany( o => o.OrderLineList ) // results in IEnumerable<OrderProductVariant> .Select( opv => opv.ProductVariant ) .Select( pv => p.Product ) .GroupBy( p => p ) .Select( g => new { Product = g.Key, Count = g.Count() });

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• Building KPIs to monitor your business Its not really about the Technology

  When I have discussions with people about Business Intelligence, one of the questions the inevitably come up is about building KPIs and how to accomplish that. From a technical level the concept of a KPI is very simple, almost too simple in that it is like the tip of an iceberg floating above the water. The key to that iceberg is not really the tip, but the mass of the iceberg that is hidden beneath the surface upon which the tip sits. The analogy of the iceberg is not meant to indicate that the foundation of the KPI is overly difficult or complex. The disparity in size in meant to indicate that the larger thing that needs to be defined is not the technical tip, but the underlying business definition of what the KPI means. From a technical perspective the KPI consists of primarily the following items: Actual Value This is the actual value data point that is being measured. An example would be something like the amount of sales. Target Value This is the target goal for the KPI. This is a number that can be measured against Actual Value. An example would be $10,000 in monthly sales. Target Indicator Range This is the definition of ranges that define what type of indicator the user will see comparing the Actual Value to the Target Value. Most often this is defined by stoplight, but can be any indicator that is going to show a status in a quick fashion to the user. Typically this would be something like: Red Light = Actual Value more than 5% below target; Yellow Light = Within 5% of target either direction; Green Light = More than 5% higher than Target Value Status\Trend Indicator This is an optional attribute of a KPI that is typically used to show some kind of trend. The vast majority of these indicators are used to show some type of progress against a previous period. As an example, the status indicator might be used to show how the monthly sales compare to last month. With this type of indicator there needs to be not only a definition of what the ranges are for your status indictor, but then also what value the number needs to be compared against. So now we have an idea of what data points a KPI consists of from a technical perspective lets talk a bit about tools. As you can see technically there is not a whole lot to them and the choice of technology is not as important as the definition of the KPIs, which we will get to in a minute. There are many different types of tools in the Microsoft BI stack that you can use to expose your KPI to the business. These include Performance Point, SharePoint, Excel, and SQL Reporting Services. There are pluses and minuses to each technology and the right technology is based a lot on your goals and how you want to deliver the information to the users. Additionally, there are other non-Microsoft tools that can be used to expose KPI indicators to your business users. Regardless of the technology used as your front end, the heavy lifting of KPI is in the business definition of the values and benchmarks for that KPI. The discussion about KPIs is very dependent on the history of an organization and how much they are exposed to the attributes of a KPI. Often times when discussing KPIs with a business contact who has not been exposed to KPIs the discussion tends to also be a session educating the business user about what a KPI is and what goes into the definition of a KPI. The majority of times the business user has an idea of what their actual values are and they have been tracking those numbers for some time, generally in Excel and all manually. So they will know the amount of sales last month along with sales two years ago in the same month. Where the conversation tends to get stuck is when you start discussing what the target value should be. The actual value is answering the What and How much questions. When you are talking about the Target values you are asking the question Is this number good or bad. Typically, the user will know whether or not the value is good or bad, but most of the time they are not able to quantify what is good or bad. Their response is usually something like I just know. Because they have been watching the sales quantity for years now, they can tell you that a 5% decrease in sales this month might actually be a good thing, maybe because the salespeople are all waiting until next month when the new versions come out. It can sometimes be very hard to break the business people of this habit. One of the fears generally is that the status indicator is not subjective. Thus, in the scenario above, the business user is going to be fearful that their boss, just looking at a negative red indicator, is going to haul them out to the woodshed for a bad month. But, on the flip side, if all you are displaying is the amount of sales, only a person with knowledge of last month sales and the target amount for this month would have any idea if $10,000 in sales is good or not. Here is where a key point about KPIs needs to be communicated to both the business user and any user who might be viewing the results of that KPI. The KPI is just one tool that is used to report on business performance. The KPI is meant as a quick indicator of one business statistic. It is not meant to tell the entire story. It does not answer the question Why. Its primary purpose is to objectively and quickly expose an area of the business that might warrant more review. There is always going to be the need to do further analysis on any potential negative or neutral KPI. So, hopefully, once you have convinced your business user to come up with some target numbers and ranges for status indicators, you then need to take the next step and help them answer the Why question. The main question here to ask is, Okay, you see the indicator and you need to discover why the number is what is, where do you go?. The answer is usually a combination of sources. A sales manager might have some of the following items at their disposal (Marketing report showing a decrease in the promotional discounts for the month, Pricing Report showing the reduction of prices of older models, an Inventory Report showing the discontinuation of a particular product line, or a memo showing the ending of a large affiliate partnership. The answers to the question Why are never as simple as a single indicator value. Bring able to quickly get to this information is all about designing how a user accesses the KPIs and then also how easily they can get to the additional information they need. This is where a Dashboard mentality can come in handy. For example, the business user can have a dashboard that shows their KPIs, but also has links to some of the common reports that they run regarding Sales Data. The users boss may have the same KPIs on their dashboard, but instead of links to individual reports they are going to have a link to a status report that was created by the user that pulls together all the data about the KPI in a summary format the users boss can review. So some of the key things to think about when building or evaluating KPIs for your organization: Technology should not be the driving factor KPIs are of little value without some indicator for whether a value is good, bad or neutral. KPIs only give an answer to the Is this number good\bad? question Make sure the ability to drill into the Why of a KPI is close at hand and relevant to the user who is viewing the KPI. The KPI is a key business tool when defined properly to help monitor business performance across the enterprise in an objective and consistent manner. At times it might feel like the process of defining the business aspects of a KPI can sometimes be arduous, the payoff in the end can far outweigh the costs. Some of the benefits of going through this process are a better understanding of the key metrics for an organization and the measure of those metrics and a consistent snapshot of business performance that can be utilized across the organization. And I think that these are benefits to any organization regardless of the technology or the implementation.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• MYSQL: Like Method, Similar Words - But Don't Show the Searched Word

  - by elmaso

  Hello, actually i use this method to show similar words for a search request.. $query = "SELECT * FROM searches WHERE Query LIKE '%$search%' ORDER BY Query"; if someone searches for "nelly" it looks up in the database for similar words "nelly furtado, nelly ft. kelly"... but i dont want to show up the searched word.. example: you've searched for nelly - try this too: nelly, nelly furtado, nelly ft., the bold word should not showed up again, because it's the searched word.. is there maybe a method with MATCH AGAINST? thank you!

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• Why do I keep on getting an exception-illegal operation on ResultSet?

  - by eli1987

  Here is the code-admittedly I'm terrible at Java, but surely I catch a null result set with the if....else statement....sorry its the whole Class: /* * To change this template, choose Tools | Templates * and open the template in the editor. */ /* * SearchParts.java * * Created on 08-Mar-2010, 12:14:31 */ package garits; import java.sql.*; import javax.swing.*; /** * * @author Deniz */ public class SearchParts extends javax.swing.JFrame { /** Creates new form SearchParts */ public SearchParts() { initComponents(); } /** This method is called from within the constructor to * initialize the form. * WARNING: Do NOT modify this code. The content of this method is * always regenerated by the Form Editor. */ @SuppressWarnings("unchecked") private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { if (!jTextField1.getText().equals("")) { String result = ""; int Partnumber = Integer.parseInt(jTextField1.getText()); DB db = new DB(); try { db.connect(); String query = "Select * from Stock Where Part_no =" + "'" + jTextField1.getText() + "'"; ResultSet rs = db.execSQL(query); if (rs.equals(null)) { PartNotFound nf = new PartNotFound(); nf.setVisible(true); } else { ResultSetMetaData rsmd = rs.getMetaData(); int numberOfColumns = rsmd.getColumnCount(); int RowCount = 0; for (int i = 1; i < numberOfColumns; i++) { rs.getString(i); result += i + "/n"; } if (!result.equals("")) { Receptionist_FranchiseePartFound part = new Receptionist_FranchiseePartFound(); part.setVisible(true); while (rs.next()) { RowCount++; } part.getTable().addRowSelectionInterval(0, RowCount); } else { PartNotFound nf = new PartNotFound(); } } } catch (Exception e) { e.printStackTrace(); JOptionPane.showMessageDialog(jButton1, "More information needed for search", "Error Message", JOptionPane.ERROR_MESSAGE); } } else if (!jTextField2.getText().equals("")) { String result = ""; DB db = new DB(); try { db.connect(); String query = "Select * from Stock Where Part_name =" + "'" + jTextField2.getText() + "'"; ResultSet rs = db.execSQL(query); if (rs.equals(null)) { PartNotFound nf = new PartNotFound(); nf.setVisible(true); } else { ResultSetMetaData rsmd = rs.getMetaData(); int numberOfColumns = rsmd.getColumnCount(); int RowCount = 0; for (int i = 1; i < numberOfColumns; i++) { rs.getString(i); result += i + "/n"; } // Receptionist_FranchiseePartFound part = new Receptionist_FranchiseePartFound(); // part.setVisible(true); if (!result.equals("")) { Receptionist_FranchiseePartFound part = new Receptionist_FranchiseePartFound(); part.setVisible(true); while (rs.next()) { RowCount++; } part.getTable().addRowSelectionInterval(0, RowCount); } else { PartNotFound nf = new PartNotFound(); nf.setVisible(true); } } } catch (Exception e) { e.printStackTrace(); JOptionPane.showMessageDialog(jButton1, "More information needed for search", "Error Message", JOptionPane.ERROR_MESSAGE); } } else if (jTextField1.getText().equals("") && jTextField2.getText().equals("")) { String result = ""; DB db = new DB(); try { db.connect(); String query = "Select * from Stock Where Manufacturer =" + "'" + jTextField3.getText() + "'AND Vehicle_type ='" + jTextField4.getText() + "'"; ResultSet rs = db.execSQL(query); if (rs.equals(null)) { PartNotFound nf = new PartNotFound(); nf.setVisible(true); } else{ ResultSetMetaData rsmd = rs.getMetaData(); int numberOfColumns = rsmd.getColumnCount(); int RowCount = 0; for (int i = 1; i < numberOfColumns; i++) { rs.getString(i); result += i + "/n"; } // Receptionist_FranchiseePartFound part = new Receptionist_FranchiseePartFound(); // part.setVisible(true); if (!result.equals("")) { Receptionist_FranchiseePartFound part = new Receptionist_FranchiseePartFound(); part.setVisible(true); while (rs.next()) { RowCount++; } part.getTable().addRowSelectionInterval(0, RowCount); } else { PartNotFound nf = new PartNotFound(); nf.setVisible(true); } } } catch (Exception e) { e.printStackTrace(); JOptionPane.showMessageDialog(jButton1, "More information needed for search", "Error Message", JOptionPane.ERROR_MESSAGE); } } else if (jTextField3.getText().equals("") || jTextField4.getText().equals("")) { JOptionPane.showMessageDialog(jButton1, "More information needed for search", "Error Message", JOptionPane.ERROR_MESSAGE); } } /** * @param args the command line arguments */ // Variables declaration - do not modify private javax.swing.JButton jButton1; private javax.swing.JButton jButton2; private javax.swing.JLabel jLabel1; private javax.swing.JLabel jLabel2; private javax.swing.JLabel jLabel3; private javax.swing.JLabel jLabel4; private javax.swing.JLabel jLabel5; private javax.swing.JLabel jLabel6; private javax.swing.JLabel jLabel7; private javax.swing.JLabel jLabel8; private javax.swing.JTextField jTextField1; private javax.swing.JTextField jTextField2; private javax.swing.JTextField jTextField3; private javax.swing.JTextField jTextField4; // End of variables declaration }

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• Detect the FTS3 extension in SQLite3

  - by pts

  What is the SQLite query to detect if the FTS3 extension module is installed? Or is it possible to get a list of installed extensions with an SQLite3 query? It has to work with pysqlite2. I know that I can get the list of tables using SELECT * FROM sqlite_master, I'd like to get something similar for the list of extensions. I also know that CREATE VIRTUAL TABLE v USING FTS3 (t TEXT) succeeds iff FTS3 is installed, but I'd like to get a query without side effects (not even creating a temporary table).

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• C#: LINQ vs foreach - Round 1.

  - by James Michael Hare

  So I was reading Peter Kellner's blog entry on Resharper 5.0 and its LINQ refactoring and thought that was very cool.  But that raised a point I had always been curious about in my head -- which is a better choice: manual foreach loops or LINQ?    The answer is not really clear-cut.  There are two sides to any code cost arguments: performance and maintainability.  The first of these is obvious and quantifiable.  Given any two pieces of code that perform the same function, you can run them side-by-side and see which piece of code performs better.   Unfortunately, this is not always a good measure.  Well written assembly language outperforms well written C++ code, but you lose a lot in maintainability which creates a big techncial debt load that is hard to offset as the application ages.  In contrast, higher level constructs make the code more brief and easier to understand, hence reducing technical cost.   Now, obviously in this case we're not talking two separate languages, we're comparing doing something manually in the language versus using a higher-order set of IEnumerable extensions that are in the System.Linq library.   Well, before we discuss any further, let's look at some sample code and the numbers.  First, let's take a look at the for loop and the LINQ expression.  This is just a simple find comparison:       // find implemented via LINQ     public static bool FindViaLinq(IEnumerable<int> list, int target)     {         return list.Any(item => item == target);     }         // find implemented via standard iteration     public static bool FindViaIteration(IEnumerable<int> list, int target)     {         foreach (var i in list)         {             if (i == target)             {                 return true;             }         }           return false;     }   Okay, looking at this from a maintainability point of view, the Linq expression is definitely more concise (8 lines down to 1) and is very readable in intention.  You don't have to actually analyze the behavior of the loop to determine what it's doing.   So let's take a look at performance metrics from 100,000 iterations of these methods on a List<int> of varying sizes filled with random data.  For this test, we fill a target array with 100,000 random integers and then run the exact same pseudo-random targets through both searches.                       List<T> On 100,000 Iterations     Method      Size     Total (ms)  Per Iteration (ms)  % Slower     Any         10       26          0.00046             30.00%     Iteration   10       20          0.00023             -     Any         100      116         0.00201             18.37%     Iteration   100      98          0.00118             -     Any         1000     1058        0.01853             16.78%     Iteration   1000     906         0.01155             -     Any         10,000   10,383      0.18189             17.41%     Iteration   10,000   8843        0.11362             -     Any         100,000  104,004     1.8297              18.27%     Iteration   100,000  87,941      1.13163             -   The LINQ expression is running about 17% slower for average size collections and worse for smaller collections.  Presumably, this is due to the overhead of the state machine used to track the iterators for the yield returns in the LINQ expressions, which seems about right in a tight loop such as this.   So what about other LINQ expressions?  After all, Any() is one of the more trivial ones.  I decided to try the TakeWhile() algorithm using a Count() to get the position stopped like the sample Pete was using in his blog that Resharper refactored for him into LINQ:       // Linq form     public static int GetTargetPosition1(IEnumerable<int> list, int target)     {         return list.TakeWhile(item => item != target).Count();     }       // traditionally iterative form     public static int GetTargetPosition2(IEnumerable<int> list, int target)     {         int count = 0;           foreach (var i in list)         {             if(i == target)             {                 break;             }               ++count;         }           return count;     }   Once again, the LINQ expression is much shorter, easier to read, and should be easier to maintain over time, reducing the cost of technical debt.  So I ran these through the same test data:                       List<T> On 100,000 Iterations     Method      Size     Total (ms)  Per Iteration (ms)  % Slower     TakeWhile   10       41          0.00041             128%     Iteration   10       18          0.00018             -     TakeWhile   100      171         0.00171             88%     Iteration   100      91          0.00091             -     TakeWhile   1000     1604        0.01604             94%     Iteration   1000     825         0.00825             -     TakeWhile   10,000   15765       0.15765             92%     Iteration   10,000   8204        0.08204             -     TakeWhile   100,000  156950      1.5695              92%     Iteration   100,000  81635       0.81635             -     Wow!  I expected some overhead due to the state machines iterators produce, but 90% slower?  That seems a little heavy to me.  So then I thought, well, what if TakeWhile() is not the right tool for the job?  The problem is TakeWhile returns each item for processing using yield return, whereas our for-loop really doesn't care about the item beyond using it as a stop condition to evaluate. So what if that back and forth with the iterator state machine is the problem?  Well, we can quickly create an (albeit ugly) lambda that uses the Any() along with a count in a closure (if a LINQ guru knows a better way PLEASE let me know!), after all , this is more consistent with what we're trying to do, we're trying to find the first occurence of an item and halt once we find it, we just happen to be counting on the way.  This mostly matches Any().       // a new method that uses linq but evaluates the count in a closure.     public static int TakeWhileViaLinq2(IEnumerable<int> list, int target)     {         int count = 0;         list.Any(item =>             {                 if(item == target)                 {                     return true;                 }                   ++count;                 return false;             });         return count;     }     Now how does this one compare?                         List<T> On 100,000 Iterations     Method         Size     Total (ms)  Per Iteration (ms)  % Slower     TakeWhile      10       41          0.00041             128%     Any w/Closure  10       23          0.00023             28%     Iteration      10       18          0.00018             -     TakeWhile      100      171         0.00171             88%     Any w/Closure  100      116         0.00116             27%     Iteration      100      91          0.00091             -     TakeWhile      1000     1604        0.01604             94%     Any w/Closure  1000     1101        0.01101             33%     Iteration      1000     825         0.00825             -     TakeWhile      10,000   15765       0.15765             92%     Any w/Closure  10,000   10802       0.10802             32%     Iteration      10,000   8204        0.08204             -     TakeWhile      100,000  156950      1.5695              92%     Any w/Closure  100,000  108378      1.08378             33%     Iteration      100,000  81635       0.81635             -     Much better!  It seems that the overhead of TakeAny() returning each item and updating the state in the state machine is drastically reduced by using Any() since Any() iterates forward until it finds the value we're looking for -- for the task we're attempting to do.   So the lesson there is, make sure when you use a LINQ expression you're choosing the best expression for the job, because if you're doing more work than you really need, you'll have a slower algorithm.  But this is true of any choice of algorithm or collection in general.     Even with the Any() with the count in the closure it is still about 30% slower, but let's consider that angle carefully.  For a list of 100,000 items, it was the difference between 1.01 ms and 0.82 ms roughly in a List<T>.  That's really not that bad at all in the grand scheme of things.  Even running at 90% slower with TakeWhile(), for the vast majority of my projects, an extra millisecond to save potential errors in the long term and improve maintainability is a small price to pay.  And if your typical list is 1000 items or less we're talking only microseconds worth of difference.   It's like they say: 90% of your performance bottlenecks are in 2% of your code, so over-optimizing almost never pays off.  So personally, I'll take the LINQ expression wherever I can because they will be easier to read and maintain (thus reducing technical debt) and I can rely on Microsoft's development to have coded and unit tested those algorithm fully for me instead of relying on a developer to code the loop logic correctly.   If something's 90% slower, yes, it's worth keeping in mind, but it's really not until you start get magnitudes-of-order slower (10x, 100x, 1000x) that alarm bells should really go off.  And if I ever do need that last millisecond of performance?  Well then I'll optimize JUST THAT problem spot.  To me it's worth it for the readability, speed-to-market, and maintainability.

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• HQL recursion, how do I do this?

  - by niklassaers

  Hi guys, I have a tree structure where each Node has a parent and a Set<Node> children. Each Node has a String title, and I want to make a query where I select Set<String> titles, being the title of this node and of all parent nodes. How do I write this query? The query for a single title is this, but like I said, I'd like it expanded for the entire branch of parents. SELECT node.title FROM Node node WHERE node.id = :id Cheers Nik

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• Problems with Date, preparedStatement, JDBC and PostgreSQL

  - by GuidoMB

  I Have to get a movie from a PostgreSQL database that matches a given title and release date. title is a character(75) and releaseDate is a date. I Have this code: String query = "SELECT * FROM \"Movie\" WHERE title = ? AND \"releaseDate\" = ?)"; Connection conn = connectionManager.getConnection(); PreparedStatement stmt = conn.prepareStatement(query); java.sql.Date date = new java.sql.Date(releaseDate.getTime()); stmt.setString(1, title); stmt.setDate(2, date); ResultSet result = stmt.executeQuery(); but it's not working because the releaseDate is not matching when it should. The query SELECT * FROM "Movie" WHERE title = A_MOVIE AND "releaseDate" = A_DATE works perfectly on a command shell using psql

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• Efficient Search function with Linq to SQL

  - by Bayonian

  Hi, I'm using VB.NET and Linq to SQL. I have a table with thousands of rows and growing. Right now I'm using .Contains() in the Where clause to perform the query. Below is my search function : Public Shared Function DemoSearchFunction(ByVal keyword As String) As DataTable Dim db As New BibleDataClassesDataContext() Dim query = From b In db.khmer_books _ From ch In db.khmer_chapters _ From v In db.testing_khmers _ Where v.t_v.Contains(keyword) And ch.kh_book_id = b.kh_b_id And v.t_chid = ch.kh_ch_id _ Select b.kh_b_id, b.kh_b_title, ch.kh_ch_id, ch.kh_ch_number, v.t_id, v.t_vn, v.t_v Dim dtDataTableOne = New DataTable("dtOne") dtDataTableOne.Columns.Add("bid", GetType(Integer)) dtDataTableOne.Columns.Add("btitle", GetType(String)) dtDataTableOne.Columns.Add("chid", GetType(Integer)) dtDataTableOne.Columns.Add("chn", GetType(Integer)) dtDataTableOne.Columns.Add("vid", GetType(Integer)) dtDataTableOne.Columns.Add("vn", GetType(Integer)) dtDataTableOne.Columns.Add("verse", GetType(String)) For Each r In query dtDataTableOne.Rows.Add(New Object() {r.kh_b_id, r.kh_b_title, r.kh_ch_id, r.kh_ch_number, r.t_id, r.t_vn, r.t_v}) Next Return dtDataTableOne End Function I would like to know other methods for doing efficient search using Linq to SQL. Thanks.

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• Unable to compare valuesfrom mysql in a prepared statement

  - by Cortopasta

  I can't seem to get this to connect to the database so that I can run my prepared statement. Does anybody have an idea what I've forgotten? private function check_credentials($plain_username, $password) { global $dbcon; $ac = new ac(); $ac->dbconnect(); $userid = $dbcon->prepare('SELECT id FROM users WHERE username = :username AND password = :password LIMIT 1'); $userid->bindParam(':username', $plain_username); $userid->bindParam(':password', $password); $userid->execute(); $id = $userid->fetch(); Return $id; } EDIT: I changed the SQL query from a SELECT FROM query, to an INSERT INTO query and it worked. WHat the heck is going on?

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• nesting classes in php

  - by Honey

  here is my sample class to why i want to nest. include("class.db.php"); class Cart { function getProducts() { //this is how i do it now. //enter code here`but i dont want to redeclare for every method in this class. //how can i declare it in one location to be able to use the same variable in every method? $db = new mysqlDB; $query = $db->query("select something from a table"); return $query } }

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• why this sql not working?

  - by user295189

  I have a query public static function TestQuery( $start=0, $limit=0){ $sql = " SELECT count(*) AS total FROM db.table1 JOIN db.table2 ON table1.fieldID = {$fieldID} AND table2.assigned = 'N'"; $qry = new SQLQuery; $qry-query($sql); if($row = $qry-fetchRow()){ $total = intval($row-total); } return $total; } which works fine but when I add the limit as below, then it doesnt work and gives me errors public static function TestQuery( $start=0, $limit=0){ $sql = " SELECT count(*) AS total FROM db.table1 JOIN db.table2 ON table1.fieldID = {$fieldID} AND table2.assigned = 'N'"; //this fails if($recordlimit 0) $sql .= "LIMIT {$startRecord}, {$recordLimit} "; // $qry = new SQLQuery; $qry-query($sql); if($row = $qry-fetchRow()){ $total = intval($row-total); } return $total; } Any help will be appreciated

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• Using JQuery getJSON method

  - by nav

  Hi, I am attempting to pase a a JSON data using the JQuery getJSON function. The REST query is: http://query.yahooapis.com/v1/public/yql?q=select%20woeid%20from%20geo.places%20where%20text%20%3D%20%22london%22&format=json&jsoncallback=? The script I'm using to parse 'data' to obtain the WOEID value doesnt seem to work below: $.getJSON("http://query.yahooapis.com/v1/public/yql?"+ "q=select%20woeid%20from%20geo.places%20where%20text%20%3D%20%22"+ "london"+ "%22&format=json&jsoncallback=?", function(data){ console.log("json: " + data); var datatmp = data; if(data.results[0]){ var data = filterData(data.results.place[0]); } } ); Can anyone say what I'm doing wrong? link text

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• Entity Framework Model with inheritance and RIA Services

  - by TimothyP

  Hi, We have an entity framework model with has some inheritance in it. The following example is not the actuall model, but just to make my point... Let's say Base class: Person Child classes: Employee, Customer The database has been generated, the DomainService has been created and we can get to the data: lstCustomers.ItemsSource = context.Persons; EntityQuery<Person> query = context.GetPeopleQuery().Take(4); context.Load(query); But how can I modify the query to only return Customers ?

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• Selecting arbitrary strings with Zend DB Select?

  - by wizzard

  I am using the fluent interface to create a Zend DB Select object/query. As part of the query, I would like to select an arbitrary string, like "SELECT 'foo' AS 'type' FROM ...". foo is not a column, it's just a string literal. When I select an arbitrary number, the query works as expected. When I change it to a string, Zend tries to treat foo as a column, and throws an error: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'l.foo' in 'field list' I have tried wrapping the string in Zend_Db_Expr in various ways such as: $select->columns(array('type' => new Zend_Db_Expr('foo'))); That stops Zend from adding the correlation name, but it still treats it as a column: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'foo' in 'field list' I feel like I must be missing something obvious here. How do I tell Zend to stop treating this as a column?

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• Automating scraping of table data to XML

  - by thewinchester

  Problem I have a YQL query result that I'm trying to get converted and sort into a clean XML file. Background Being the pains that they are, information from the World Cup isn't freely available in an easy to reuse format. So, after a bit of finessing with YQL I have managed to liberate the required table rows which contain the data I'm after. The YQL query can be viewed at: http://query.yahooapis.com/v1/public/yql/ravingbeefsteak/worldcup2010groupliberator?diagnostics=true I'd like to now convert this information into XML, and being an absolute n00b I don't know where to start or what to look for. I'm also needing to do a find and replace on the data to get the URL's working as they should without manual changes, and hopefully an initial sorting of the data. If anyone can point me in the right direction of what I need to be doing to make my needs a reality it would be greatly appreciated.

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• IEnumerable<> to IList<>

  - by nachid

  I am using Linq to query my database and returning a generic IList. Whatever I tried I couldn't convert an IQueryable to an IList. Here is my code. I cannot write simpler than this and I don't understand why it is not working. public IList<IRegion> GetRegionList(string countryCode) { var query = from c in Database.RegionDataSource where (c.CountryCode == countryCode) orderby c.Name select new {c.RegionCode, c.RegionName}; return query.Cast<IRegion>().ToList(); } This returns an list with the right number of items but they are all empty Please help, I am bloqued with this for a couple of days now

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• Nested queries in Arel

  - by Schrockwell

  I am attempting to nest SELECT queries in Arel and/or Active Record in Rails 3 to generate the following SQL statement. SELECT sorted.* FROM (SELECT * FROM points ORDER BY points.timestamp DESC) AS sorted GROUP BY sorted.client_id An alias for the subquery can be created by doing points = Table(:points) sorted = points.order('timestamp DESC').alias but then I'm stuck as how to pass it into the parent query (short of calling #to_sql, which sounds pretty ugly). How do you use a SELECT statement as a sub-query in Arel (or Active Record) to accomplish the above? Maybe there's an altogether different way to accomplish this query that doesn't use nested queries?

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