Lesson 1: Reconciling Data Conflicts in Visual Basic .NET

Printing QR Code in Visual Basic .NET Lesson 1: Reconciling Data Conflicts

If the Keep The Subscriber Change conflict resolution policy is enforced, the last Subscriber transaction to update the Publisher is retained. You can view conflict data using the Microsoft Replication Conflict Viewer. Conflict data is stored until the end of the conflict retention period (a default of 14 days).

You can use the following questions to test your knowledge of the information in Lesson 1, Reconciling Data Conflicts. The questions are also available on the companion CD if you prefer to review them in electronic form.

Answers to these questions and explanations of why each answer choice is correct or incorrect are located in the Answers section at the end of this book.

1. Which conflict resolution policy ensures that the publisher is always updated when a Subscriber synchronizes with new data A. Keep The Publisher Change B. Reinitialize The Subscription C. Keep The Subscriber Change 2. Which SQL Server 2005 subsystem detects data conflicts during Subscriber/ Publisher synchronization A. SQL Server Integration Services B. SQL Server Agent C. Queue Reader Agent D. SQL Server Analysis Services 3. Ian enters some changes to correct a row on a Subscriber database. When he checks back an hour later, he notices that the row has changed but that the changes are different from the ones that he entered. He checks and finds that a conflict occurred. Which of the following conflict resolution policies might apply to the publication (Choose all that apply.) A. Keep The Publisher Change B. Reinitialize The Subscription C. Keep The Subscriber Change

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As you might remember from the study you have undertaken for previous SQL Server 2005 exams, constraints are limitations on the data that users can insert in a column of a database table. UNIQUE or PRIMARY KEY constraints prevent users from inserting a value that already exists within the column, and CHECK constraints prevent users from inserting values that do not meet a particular rule. In the context of SQL Server 2005, an implicit constraint is a business rule. Implicit constraints could be anything from no contractor can bill more than 60 hours in a week to the maximum number of items that a customer can order at any one time. As a database administrator, you might be responsible for ensuring that the database reflects the policy rules of the business. An explicit constraint is one that the administrator applies to the database. Following from the example just mentioned, the database administrator would implement an explicit constraint by programming the database so that it would be impossible for a contractor to enter a value higher than 60 hours per week into the organization s billing database.

After this lesson, you will be able to:

Make implicit constraints explicit. Define primary key constraints. Define unique constraints. Define check constraints. Define foreign key constraints. Apply default definitions to columns. Configure the nullability of columns. Define triggers.

You can think of an implicit constraint as a business or organizational rule. An example might be that all employees within a particular department always have a salary range between 40 and 60 thousand dollars a year. To make this implicit constraint explicit, you must devise a way to ensure that the database does not allow users to enter values outside this range.

Constraints determine whether users can store particular data in a column depending on a particular rule. This rule might be as simple as allow any value to be stored in this column except values that are already stored within this column. Constraints can also be more complex, allowing users to insert into a table s column only values that conform to a particular logical rule. The following types of constraints are covered over the next few pages: