Databases and ADO.NET Programming Right from the Start with Visual Basic.NET 1/e 11

Databases andADO.NET

Programming Right from the Start with Visual Basic .NET 1/e

11

Crews/Murphy – Programming Right from the Start with Visual Basic.NET 1/e – ©2004 Prentice Hall 2

Objectives

• Understand databases and the relational database model

• Understand primary keys and foreign keys

• Understand simple SQL queries

• Use WHERE and ORDER BY clauses

• Query multiple tables using JOIN

• Create a Connection object


Objectives (cont.)

• Create and work with a DataAdapter object

• Create and work with a Dataset object

• Work with data bound controls

• Work with the DataGrid control

• Develop applications that interact with a database


11-1 Database Primer

• A database is a structured collection of data.

• A field is a storage location for a single piece of information.

• A record is a complete collection of related fields.

• A table is a complete set of related records.


11-1 Database Primer (cont.)


Relational Databases

• In the relational database model, relationships exist between tables to indicate how the data is connected.

• Relationships involve the primary key from one table and a foreign key in a related table.


Relational Databases (cont.)

• The primary key is a field (or set of fields) that uniquely distinguishes the records in a table.

• The foreign key contains values that match primary key values in a related table.

• The primary key and foreign key fields are essential for creating the relationships between tables.







• The Customers table and the Orders table have a one-to-many relationship.

• Students and Classes have a many-to-many relationship.

• A many-to-many relationship is usually implemented using a linking table with foreign keys to each of the two original tables.


11-2 Structured Query Language (SQL)

• An application communicates with a DBMS through queries written in a standard language called Structured Query Language (SQL).

• SQL is an industry standard language that allows an application to communicate with a relational database.


SELECT Query

• The SELECT command is used to select specific information from one or more tables in a database.– SELECT fields FROM table


WHERE Clause

• The WHERE clause provides the database the capability to choose information based on selection criteria.– SELECT fields FROM table WHERE criteria

• The WHERE clause condition can contain >, <, =, <>, >=, <=

• LIKE, *, and ? can also be used


ORDER BY Clause

• The information returned by a SELECT statement can be arranged in ascending or descending order with the ORDER BY clause.– SELECT fields FROM table [WHERE criteria]

ORDER BY field [ASCIDESC]

• ASC specifies ascending order; DESC specifies descending order.


JOIN

• To create a query that combines data from multiple tables, you use the JOIN operation.– SELECT fields FROM table1 [LEFT|RIGHT]

JOIN table2 ON table1.field1 = table2.field2

[WHERE criteria]

[ORDER BY field]


11-3 Using ADO.NET

• ADO.NET is the data access architecture for the .NET Framework.

• ADO.NET provides Connection, Data-Adapter, and Dataset objects to facilitate accessing data in a database.


11-3 Using ADO.NET (cont.)


Creating a Connection

• A Connection object establishes a link from your application to a database file.

• A connection object specifies the type and location of the database file.

• Step 1: Create a Connection is to select an OleDbConnection control from the Toolbox


Creating a Connection (cont.)

• Step 2: Create a Connection is to add an OleDbConnection object to the component tray.

• Step 3: Select a New Connection for the control.

• Step 4: Select the appropriate database provider and the path/filename of the database.


Creating a DataAdapter

• Once a Connection has been established, the next step is to create a DataAdapter.

• A DataAdapter passes information between the database and your application.

• The SQL command is part of the DataAdapter.


Creating a DataAdapter (cont.)

• Step 1: Add an OleDbAdapter control which starts a Wizard

• Step 2: Specify the Connection to use for the DataAdapter

• Step 3: Select a Query Type

• Step 4: Specify the SQL statements

• Step 5: Save the settings


Creating a DataAdapter (cont.)


Generating a Dataset

• Once you have established a Connection and a DataAdapter, the next step is to create a Dataset.

• A Dataset in ADO.NET is a temporary, local copy of the information in the table.

• To create a Dataset, right-click on the object and select Generate Dataset from the pop-up menu.


11-4 Displaying andNavigating Records

• The information in a Dataset can be viewed by means of one or more data-aware controls.

• A data-aware control is a control that can be bound to a Dataset; when bound, the control automatically displays the information it receives from the Dataset.


The Fill Method

• The Fill method of the DataAdapter is used to populate the Dataset.– DataAdapter.Fill(DataSet)


Dataset Navigation

• When text boxes are data bound they display their specified field values for the current record in the specified dataset.

• Each form has a BindingContext object that keeps track of all the data sources associated with the form.

• The BindingContext has a position property and a Count property.


11-5 The DataGrid Control• The DataGrid control is designed to

display ADO.NET data in a scrollable grid.

• The DataSource property specifies the name of the data source from which the grid will get data.

• The DataMember property specifies which table or other element to bind to if the data source contains more than one bindable element.


Chapter Summary

• A database is a collection of one or more structured sets of data.

• A table is a two-dimensional matrix of rows and columns.

• A foreign key is a field in a table that refers to the primary key in another table.


Chapter Summary (cont.)

• An application communicates with a DBMS through queries written in SQL.

• The SELECT command is used to select specific information from one or more tables in a database.

• The WHERE clause is used to choose information based on selection criteria.


Chapter Summary (cont.)• The results of a query can be arranged in

ascending or descending order with the ORDER BY clause.

• Relational databases store data over multiple tables to eliminate data redundancy.

• A Connection object establishes a link from your application to a database and specifies the type and location of the database.



• Once a Connection has been established, the next step is to create a DataAdapter.

• Once a Connection and a DataAdapter have been established, the next step is to create a Dataset.

• A Data-aware control is a control that can be bound to a Dataset.



• Each form has a BindingContext object that keeps track of all the data sources associated with the form.

• The DataGrid control is designed to display ADO.NET data in a scrollable grid.

Databases andADO.NET

Programming Right from the Start with Visual Basic .NET 1/e

11

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Databases and ADO.NET Programming Right from the Start with Visual Basic.NET 1/e 11