DATABASE DESIGN AND CREATION in visual C#

Embed 2d Data Matrix barcode in visual C# DATABASE DESIGN AND CREATION

Before you read on, look back at Table 3-4. The predicate month_no > 8 gives a cardinality of 437, and the predicate month_no <= 8 gives a cardinality of 864. Since every row in the table must meet exactly one or other of these two predicates (given that we have no nulls), what cardinality do you think the optimizer will return for the following clause where or month_no > 8 month_no <= 8 There are three possible guesses: It will return 1301, because that s what you get by adding the cardinalities of the two individual predicates that obviously don t overlap. It will return 1200, because the combined predicate clearly describes all the rows in the table, and there are 1,200 rows in the table. It will return 986, because that was the last test I did in the script ranges.sql, and that s what actually happened. The third argument is always compelling, even when the result is apparently irrational. And just to make things a touch more confusing, Table 3-6 shows the cardinalities you get on this query as you change the constant (see script ranges_02.sql in the online code suite).

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Try It Out: Propagating New Dataset Rows to a Data Source Let s again modify Listing 8-4 to delete a row from the database. 1. Add a new Console Application project named PersistDeletes to your 08 solution. 2. Replace the code in Module1.vb with the code in Listing 8-7.

Note that you can also view the dependencies of your application by looking at the application manifest file. For simple applications, you don t have to worry about what files are downloaded; Visual Studio and ClickOnce take care of everything for you. Other applications will require special attention, though. For example, consider a large application that is deployed under various licenses: Enterprise, Professional, and Standard. Users of the system can download the application and then enter a license key to activate a particular version. In this scenario, it does not make sense for the user to download the entire application all at once if they need only a subset of the system. It may make more sense for you to partition the application so a user can download each partition on demand. This particular scenario becomes more serious when you consider the options for protecting against software piracy. For example, if you deploy the entire code base of your application to all of your users and rely on a license to determine what modules to enable, hackers can find ways to get around the licensing issues and enable other modules. A better solution is to not deploy the unnecessary modules. ClickOnce offers a facility that can assist with these types of scenarios called on-demand download. The idea behind on-demand download is that you create groups of files and then use the ClickOnce APIs to download each group at runtime. This approach offers the benefit of reducing the overall download the initial download is reduced to what needs to be downloaded to run the application, and if a piece of functionality is not needed, it is not downloaded.

Consider enhancing the app even more by adding these features: Save the most recently entered locations to allow quicker access. Allow the user to choose what audio device is used to play back sound. Write a new Screen that can be used to play back SVG or Plazmic content. It doesn t make sense to go overboard with this app after all, BlackBerry devices have a good Media application built in. However, these sorts of enhancements help a great deal when determining how feasible it is to add certain types of content into your own apps.

// Shallow copy creates another name for the array. array<int>^ array2 = array1; array2[0] = 100; // This prints "100" since array2 is a synonym of array1. Console::WriteLine( "{0}", array1[0] ); array<int>^ array3 = gcnew array<int>(3); Array::Copy(array1, array3, array1->Length); // Change a value in the new copy of the array. array3[0] = 200; // This prints "100 1 2" since the old array was not affected. Console::WriteLine( "{0} {1} {2}", array1[0], array1[1], array1[2]); } Here is the output of Listing 5-30: 100 100 1 2

This private method determines if a given link falls within the set of links being crawled by this crawler s instance: