CS 112D Lecture Notes - Database Basics with VB.NET (Chapter 1) - Craig Persiko
SQL Server Data Types
The data types used in SQL Server have different names than in Access or VB. Here are the most important
ones for us:
- boolean - like VB's Boolean
- datetime - like VB's Date
- float - like VB's Double
- int - like VB's Integer
- varchar - like VB's String
Building a Database in Visual Studio .NET
- You can build a database and its tables, etc. using VS.NET's Server Explorer, as outlined in your
- There is a typo on page 12: column name is Email, not E-mail.
- You can create database diagrams using Server Explorer or Visio. Visio is more poweful, but it only
comes with the Enterprise Architect edition of VS.NET, so we won't use it in this class.
Database Concept Review
- Database - a collection of Tables, Queries, etc. containing all the data relating to a
particular area (such as one company's records)
- Table - stores a category of data, e.g. Customer
- Field - one piece of data from a table, e.g. First Name
- Record - one value for each field, e.g. one customer's data from the table
- Primary Key - field that acts as unique record identifier (e.g. ID)
- Index - speeds up sorting by one field (or a combo of fields)
- Relationships (e.g. One-to-One, One-to-Many, Many-to-Many) - when one field in one table
corresponds to a field in another table. Many-to-Many relationships require a juncture table.
- Referential Integrity - ensures corresponding records exist in related tables. May include
Cascading Updates and/or Cascading Deletes
- Normalization - guidelines to ensure flexibility of data use and no repetition of information
- Query - a piece of SQL code executed on a database to modify or retrieve data.
Using VB.NET to connect to a database
- Before .NET, a Data Control was used in Visual Basic to coordinate data connections with GUI
controls. The Data control has been removed for .NET, in favor of automatically generated object code
(which is more flexible)
- In VB.NET, objects are used to connect to a database. We will study several of these classes in
detail, but following is a brief overview of the major classes we'll use:
- SqlConnection - a class which maintains a connection to a database
- SqlDataAdapter - a class which retrieves data from a SqlConnection
- DataReader - a class which stores and provides read-only access to data retreived from a
- DataSet - Like a DataReader, but also includes the ability to change the data.
- The Fill method of the DataAdapter must be called to link it to a DataReader or DataSet.
- Once objects of the above 3 classes have been setup, a Windows control can be bound to a DataReader
or DataSet, automatically displaying the data that's been retrieved.
- DataGrid - a VB control which provides a grid view of all the data stored in a table.
- To bind a DataGrid to a DataSet, set the DataGrid's DataSource property to the name of the
- The DataGrid has a DataMember property which stores the name of the table to be displayed.
- Step-by-step instructions for viewing data in a DataGrid start on page 36 of your textbook.
- There is a typo on page 37: in the middle of the page under number 3, the second line of code should
ByVal e As System.EventArgs) Handles _
- Step-by-step instructions for viewing data one record at a time in TextBoxes start on page 38 of
- There is also a typo on page 39 in the middle of the page under number 3: the last line of the Sub
Me.BindingContext(DsCustomer1, "tblCustomer").Position -= 1
- To bind a TextBox to a DataSet, go to the (DataBindings) section and set the Text
property to the field you wish to be displayed. Or in code, call the Add method of the DataBindings
property of the TextBox.
- To navigate between records in a DataSet, you need to call your form's BindingContext property,
which has a Position property. Add to the position to move forward in the DataSet.
Modifying Records using Data-Aware Controls
- Using code such as described above, data may be changed, but those changes will not be saved to the
database; the DataSet in memory is the only thing that gets changed.
- To save changes to a DataSet, the DataAdapter's Update method must be called with that
DataSet as the argument.
- Changes to the current record aren't saved unless the BindingContext's current edit is finished. This
happens automatically if you navigate to a new record, or you can call EndCurrentEdit() on the
BindingContext to make it end the current edit. Then calling Update on the DataAdapter will save the
- To create a new record in a DataSet, use the AddNew() method of the form's BindingContext
property. Moving off the new record should save changes, as will a call to the DataAdapter's Update
- To cancel an edit of a new or existing record, use the CancelCurrentEdit() method ofthe
- To delete a record from a DataSet, use the RemoveAt method of the BindingContext, specifying
the record number (Position) as the argument.
VB Syntax Note: With ... End With blocks
When you're calling a lot of methods of a particular object, you can use a With ... End With
block to specify set a default object for all method calls. Here is an example. The following code will
delete the current record from a DataSet from the Customer table:
And here is the same code using a With...End With block:
With Me.BindingContext(DsCustomer1, "tblCustomer")
Validating Data Entry
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