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Creating Report Sample Codes In Lesson 22 and Lesson 23, we have learned how to build VB database applications using data control.
While these values can be provided manually, when using ad-hoc SQL statements any customizations will be overwritten when the Table Adapter Configuration wizard is completed.
When building a Data Access Layer using Typed Data Sets, the tools work better when using subqueries. Over the next several steps we will create a Table Adapter that, initially, uses a main query that omits any that returns additional columns from related tables.
In particular, the Table Adapter s wizard will not auto-generate corresponding SELECT Product ID, Product Name, Products. Category ID, Quantity Per Unit, Unit Price, Units In Stock, Units On Order, Reorder Level, Discontinued, Categories. Company Name as Supplier Name FROM Products LEFT JOIN Categories ON Categories. Finally, we'll create a corresponding Business Logic Layer class and demonstrate using the Table Adapter in an ASP. For this tutorial we will add a Table Adapter and strongly-typed Data Table for the when initially creating the Table Adapter precludes the wizard from automatically generating the corresponding insert, update, and delete capabilities.
The SELECT Product ID, Product Name, Supplier ID, Category ID, Quantity Per Unit, Unit Price, Units In Stock, Units On Order, Reorder Level, Discontinued, (SELECT Category Name FROM Categories WHERE Categories. Category ID) as Category Name, (SELECT Company Name FROM Suppliers WHERE Suppliers. Supplier ID) as Supplier Name FROM Products SELECT Product ID, Product Name, Products. Category ID, Quantity Per Unit, Unit Price, Units In Stock, Units On Order, Reorder Level, Discontinued, Categories. Company Name as Supplier Name FROM Products LEFT JOIN Categories ON Categories. Their advice, then, is to use the technique that you and your team are most comfortable with. That means all of the customizations we later made would be lost if we right-clicked on the Table Adapter, chose Configure from the context menu, and completed the wizard again.
It merits noting that after imparting this advice these experts immediately express their preference of s over correlated subqueries. The brittleness of the Table Adapter s auto-generated stored procedures and re-run the Table Adapter Configuration wizard without having to fear that the stored procedures will be modified.
To retrieve data from two different tables we can use either a correlated subquery or a JOIN operation.
In this tutorial we compare correlated subqueries and the JOIN syntax before looking at how to create a Table Adapter that includes a JOIN in its main query.
Second, change the Object Data Source s table, causing the delete to fail.
Figure 15: Deleting an Employee That has Corresponding Orders Results in a Foreign Key Constraint Violation (Click to view full-size image) To allow an employee to be deleted you could: s provide two different techniques for accessing data from related tables in a query.
Secondly, insert the ADO data control and name it as ado Books and change its caption to book.
The following example will illustrate how to build a relatively powerful database application using ADO data control. First of all, name the new form as frm Book Title and change its caption to Book Titles- ADO Application.
To be able to use ADO data control, you need to insert it into the toolbox.