c# create barcode image Part IV in .NET

Writer Quick Response Code in .NET Part IV

Part I:

=IF(AND([DateAquired]<1/1/2006,>=10/1/2005),[Price]-[Price]*30%, IF([DateAcquired]<10/1/2005,[Price]-[Price]*50%,[Price]))

EXEC dbo.GetOrders '20080506';

Build your awareness of the development process The more aware you are of the development process, whether from reading or from your own observations about software development, the better position you re in to understand changes and to move your group in a good direction.

Changing DCHP Server Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-22

The Standard User with Administrative Links role has, as you d suspect, the Standard User role access plus membership in groups that gives users assigned this role the ability to perform administrative tasks. Click the Groups link to view the groups that this role includes.

Let s create your first chart. Just as with views, you can copy from an existing chart as a template. However, for this example, we ll create a chart from scratch.

As I ve already mentioned, explicit constraints are not the only means of enforcing data integrity. Data types are constraints as well; they constrain with type-de ned constraints and with sets of operations allowed. An attribute is constrained with its data type. You can also de ne whether a column of a table allows NULLs. Finally, the de nitions of tables constrain as well: if you don t have a place to insert a value, you cannot insert it. I will explain this a bit more in the normalization section of this chapter. You cannot implement all business rules by using declarative means. Some constraints are too complex, and some span a database boundary. A foreign key, for example, is limited to associating tables in the same database only. Some constraints have to be implemented programmatically. You can put your constraining code in a client application, in the middle tier, in the data access layer, in stored procedures in a database, or anywhere you have some code. However, if you want your RDBMS to enforce complex constraints automatically, you have to use triggers. Triggers are special stored procedures that an RDBMS executes, or res, automatically. You can use Data Modi cation Language (DML) triggers to enforce data modi cation rules and Data De nition Language (DDL) triggers to enforce schema modi cation rules. Triggers can re before or after the statement that is modifying the state of a database. SQL Server 2008 supports two kinds of DML triggers: INSTEAD OF and AFTER triggers; only one kind of DDL trigger is supported: the AFTER. INSTEAD OF triggers are not actually ANSI-standard BEFORE triggers; they do re before the statement, but they also intercept the statement, and then you can do whatever you want in the body of the trigger. If you want the statement to execute, you have to write it explicitly in the body of the trigger. In theory, you should always be able to use a view instead of a base relation. However, not all views are updatable. For example, a view can summarize some attributes of a base table; an RDBMS doesn t know how to distribute a value from a single row from a view over multiple base rows. INSTEAD OF triggers are especially meant for making views updatable. SQL Server 2008 also has a built-in XML system type. The XML type enforces some integrity rules by itself: it allows well-formed XML only. In addition, you can validate XML values against a prede ned schema from a schema collection you create inside a SQL Server database. Details of triggers and XML validations are beyond scope of this chapter; for more, please refer to Inside Microsoft SQL Server 2008: T-SQL Programming. You can also use some elements of a database that don t really enforce data integrity but instead help users insert correct values. Defaults can help insert a value when it is not explicitly listed in the INSERT statement. SQL Server 2008 has also a Timestamp type; SQL Server inserts and updates values of this type automatically and guarantees that values in

Lesson Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-74