CHAPTER EIGHT Accessing Data Processing Databases

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Introduction Data is efficiently managed by storing them in files on disk. Data files and programs are separate. The program does not need to be modified when the data changes. Different programs can share the same data sets.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Introduction (cont.) Most businesses organize their data into databases. A database is an organizes collection of data. A database management system (DBMS) is a program that is used to create and maintain databases. Visual Basic.NET provides tools for developers to access databases from their programs.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Objectives Understand and use relational databases. Understand a subset of the ADO.NET object model. Apply the ADO.NET object model within Visual Basic.NET to access databases. Use the properties and methods of the DataGrid control to display record from a DataSet.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Objectives (cont.) Write SQL Select queries to extract data from a database. Bind controls such as TextBoxes and Labels to a DataSet. Create Master/Detail DataSets. Use several tools within Visual Basic.NET to manage and use databases.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved A Relational Database Primer Entities and Relationships –Every database contains: Entities – anything of interest to a business. Relationships – real-world associations between entities. –Database developers often use an entity- relationship diagram (ERD). To document a database’s structure. Symbols are used to designate relationships between entities.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved A Relational Database Primer (cont.) Relational Database Tables –A relational database stores the data for each entity in a table with rows and columns. –Compatible with Visual Basic.NET. –A key field guarantees the uniqueness of records. –A combination key is a key field with a combination of two or more fields.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved A Relational Database Primer (cont.) –One-to-Many Relationships Established by placing the key field of the “one” entity’s table into the “many” entity’s table as a foreign key. –Many-to-Many Relationships Constructed by creating a new table with the key fields from related tables.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved A Relational Database Primer (cont.) –Normalized Databases Normalization is a process used to eliminate or reduce data redundancy. Designers must determine which tables to place information in. A table should be in third normal form.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved A Relational Database Primer (cont.) Database Queries –Most relational database systems use a query language called structured query language (SQL). To specify how to combine data in related tables. To specify how to select only the desired data.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved An Introduction to ADO.NET Visual Basic.NET uses ADO.NET to manage data in a database. –ADO.NET (ActiveX Data Objects) uses an extensive set of classes to manage data. –This chapter covers the foundations of ADO.NET. –Also we will cover some of the wizards and tools provided to work with relational databases.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved An Introduction to ADO.NET (cont.) An Overview of ADO.NET –A DataProvider object directly interacts with a database and its DBMS. –A Connection object makes the physical connection to the database. –A DataAdapter acts as an intermediary between the database and the dataset. –A DataSet class holds the actual data. –A DataRelation includes information on how tables are related. –User interface components work directly with the DataSet.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved DataSet DataProvider User Interface Components DataBase DBMS DataTable DataRelation DataAdapter Connection

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET Data Access Using the DataGrid Control –DB_sample1 –Provides a method of displaying records from a database in a grid-like manner. –Building the DataAdapter Create a DataAdapter by a wizard. –Building the DataSet Follow the procedure to create a DataSet.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) –Adding the DataGrid Follow the procedure to add a DataGrid to the form. Set the DataGrid properties to connect it to the DataAdapter and DataSet. Found on the Windows Form tab in the Toolbox. Will display fields specified in the SQL Select statement.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) The DataGrid Control –Designed to display the data stored in a DataSet. –An expander allows navigation from a parent table to a child table. –A detail list on p. 346 (Table 8.1)

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) –Properties AllowSortingCurrentCell AlternatingBackColorCurrentRowIndex (0 based) BackColorDataMember BackgroundColorDataSource BorderStyleEnabled CaptionBackColorFirstVisibleColumn CaptionFontForeColor CaptionForeColorGridLineColor CaptionTextGridLineStyle CaptionVisibleHeaderBackColor ColumnHeadersVisibleHeaderFont

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) –Properties (cont.) HeaderForeColor ParentRowsBackColor ParentRowsForeColor ParentRowsVisible PreferredColumnWidth ReadOnly RowHeadersVisible RowHeaderWidth SelectionBackColor SelectionForeColor

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved To set the current cell –DataGrid1.CurrentCell = New DataGridCell(1, 1)

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) –Methods Collapse(row) Expand(row) IsExpanded(row) IsSelected(row) Select(row) SetDataBinding(dataSourceObject, dataMemberString) UnSelect(row)

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Config Data Access without using Wizard DB_sample2 Create DataAdapter Create Connection Set up the SelectCommand, InsertCommand, UpdateCommand, DeleteCommand –Connection and CommandText properties Create DataSet

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) Updating a Table –ADO.NET provides support for table update. –Changes in the DataGrid can be relayed back to the original source data. –OleDbDataAdapter1.Update(DsStudents1) –DB_sample1 (with Update added)

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) Parameterized Queries –DB_sample3 –Users will often want to specify information that will determine the results of a query. –A parameter of a query could be a StudentID. –SELECT studentID, name FROM Students WHERE studentID = “S00001” –SELECT studentID, name FROM Students WHERE name = ?

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) Data binding refers to the process of associating one or more properties of a VB control to a specific data source. Simple data binding –Bound to a single data element (e.g. a field) Complex data binding –Bound to more than one data element in a dataset

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Using ADO.NET with Visual Basic.NET (cont.) Master/Detail Record Display –Here we examine a DataSet that includes two tables related to a common field. –A master/detail DataSet is a dataset with more than one table. –Each master record is related to zero or more records from the second table. –Parent and child terms may refer to master and detail records.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Additional Visual Basic.NET Database Tools We look at using the Server to work with databases. We show how to add a data connection to the server. The data connection will be used to create a data adapter and data set.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Chapter Summary A database is an organized collection of data and relationships that describe entities of interest to a business. An entity-relationship diagram (ERD) documents entities and their relationships. Visual Basic.NET supports the relational database approach for organizing data. Normalization is process used to minimize data redundancy.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Chapter Summary (cont.) Visual Basic.NET uses ADO.NET to access and manage databases. The DataGrid control is a control that can be bound to a specific dataset. Parameterized queries provide for the ability to determine how records will be selected at run time. Many of Visual Basic.NET’s controls can be bound to a dataset and its fields.

McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc. All rights reserved Chapter Summary (cont.) ADO.NET supports master/detail record relationships. The Server Explorer provides access and management tools for connections and servers.