Binding Data to Controls

Most of the controls in the Toolbox are bindable, which means that we can assign a column, or sometimes a group of columns, from a database table to be displayed as their contents. As you move through the rows of a table, the contents of the chosen column or columns will appear in the control. Other bindable controls include TextBoxes, Labels, CheckBoxes, ComboBoxes and Li stBoxes. Most of these controls work by setting their DataBindings.Text property to the name of the table column that you...

First Normal Form

To achieve First Normal Form, we must eliminate any repeating groups. In First Normal Form, we simplify our database structure to eliminate any repeating groups. In other words, First Normal Form includes the concept that fields must be atomic or a field represents one type of value for all records. Examples of these repeating groups can be A list of multiple values in the same field. An example would be a field containing the single string 5 - Tofu, 4 - Jack's New England Clam Chowder. The...

Filtering Data with WHERE

In the previous example, we selected all records from certain columns in the Products table. What if we only want to see products that sell for less than 25 When we want to filter data so that only records meeting certain criteria are retrieved, we can use a WHERE clause in our SQL statement, as shown below SELECT ProductName, UnitPrice, UnitsInStock FROM Products WHERE UnitPrice lt 25 The WHERE clause specifies that the UnitPrice should be less than 25, so that the above SQL statement will...

The User Interface

So you've learned how to design a database and how to update information in it using suitable SQL statements. We can't expect our users to open up an administrative database tool and manipulate the data directly like this, so our next step is to create some way for users to access information. This is the role of the user interface - to provide a means of communication between the user and the database. Through the user interface, users may interact with data and manipulate it in order to...

Tkt Programming

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Info

If you look at the DataGrid control on the designer, you'll notice that it now shows exactly ten rows and that a set of page navigation buttons has appeared at the bottom. 4. Make these changes to btnSearch_Click in PriceCheck .aspx. vb Private Sub btnSearch_Click ByVal sender As System.Object, _ ByVal e As System.EventArgs Handles btnSearch.Click Dim connection As New SqlConnection Global.DbString connection.Open ' Retreive the items Dim sql As String _ SELECT productname, unitprice,...

Responding to Order Requests

Now that we can detect when a new file has been received, we should look at processing the order and sending the response by e-mail. Unlike the Web Service model, e-mail gives us maximum flexibility -we don't have to process an order as soon as we receive it and if we want, we can collect all orders received in a day and process them as a single batch. Imagine we receive an order for 100 widgets, but we only have 60. We ship 60, and create and e-mail an XML response document that informs the...

Flat File versus Relational Databases

Flat files are the most basic form of database - all of the information is stored in a single file. A flat file includes a field for every item of information that you need to store. While they are easy to create and can be useful in certain situations, flat files are not very efficient. They can be quite wasteful of storage space, containing a lot of duplicated information, especially in a complex system where multiple files hold connected information. This can make information harder to...