Matakuliah
Tahun
Versi
: D0524 / Algoritma dan Pemrograman Komputer
: 2005
:
Pertemuan 09
Database
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Menerapkan penggunaan database dalam
aplikasi
2
Outline Material
•
•
•
•
•
•
Introduction to Database
Stored and Index Ordering
Using ADO with Visual Basic
Dataset
Datagrid
Common Programming Errors and
Problem
3
Introduction to Databases
• Database: any collection of related data used by
an organization
• Organization: any self-contained social unit such
as a company, university, hospital, or family
• The data in a database consist of two types:
– Entities
– Relationships
• Relational database: a database in which data is
stored in tables
4
Introduction to Database
• Record: a row in a table
• Field name: the heading of a column in a table
• Entity-relationship diagrams (ERDs) express the
relationships between entities
• Cardinality of a relationship refers to the number
of one entity that is related to another entity
5
Introduction to Database
Related to Exactly One
Related to One or More
Related to Zero or One
Related to Zero or More
ERD Symbols
6
Introduction to Database
Manajer
Departemen
Karyawan
Kendaraan
Operasional
Example of ER Diagram
7
Stored and Index Ordering
• Stored order
– A table’s original order
– Determined by the order in which records have been
added to the table
• Index: a separate table of record positions,
called pointers, which lists the positions of the
table’s records in the desired order
• Key field: the field on which a table’s records are
ordered
8
Using ADO with Visual Basic
• ADO is an extremely powerful data access
component that allow you to access database
data in many formats
• Using databases in Visual Basic
– Create a link or connection between the database,
known as the data source, and the Visual Basic
application
– Retrieve fields from tables in the database and
display them on a Form
– Store values on the Form in the database
9
Using ADO with Visual Basic
• To use a database, an application must:
– Set up a connection to a data source
– Create a data adapter to handle the transfer
of data to and from the data source and the
application
– Create a dataset to hold the data in memory
while the application works with it
– Add controls to the form and set their
properties to bind the controls to the fields in
the dataset
10
Using ADO with Visual Basic
Data
Source
Connection
Data
Adapter
Dataset
Setting up Data Access in Visual Basic
Windows
Form
11
Setting Up a Data Connection
• Any database that is ODBC (Open DataBase
Connectivity) compliant can be accessed from
within Visual Basic
• Visual Basic provides a set of Data controls in
the Toolbox that are used to set up database
access
• To establish a connection to an Access
database:
– Select the OleDbConnection object
– Drag an OleDbConnection control from the Toolbox to
the Form
12
Setting up a Data Adapter
• The data adapter passes data back and
forth between a data source and a
program
• Use the OleDbDataAdapter control for a
Microsoft Access database
• Data Adapter Configuration Wizard
simplifies the task of using a database
table
13
Setting up a Data Adapter
First Screen of the Data Adapter Configuration Wizard
14
Creating a Dataset
• Dataset: a copy of the data that is
retrieved from the database and then
inserted into memory
• To create a dataset:
– Select the OleDbAdapter control
– Right-click on the control and select Generate
dataset
– Generate dataset dialog box opens
15
Binding Data to Controls
• Data binding: the process of connecting a
control to one or more data elements
• A data-aware control is capable of
automatically displaying data from a
field(s) in a dataset
• Simple binding connects one control to
one data element
• Complex binding is used when more than
one data element is bound to a control
16
Filling the Dataset
• The data adapter’s Fill method
– Used to fill the dataset at run-time
– DataAdaptername.Fill(DataSetName)
17
Navigating through the
Dataset
• BindingContext object manages all of the
data bindings for the controls on the form
• CurrencyManager object provides a
simple way to navigate among the rows in
a dataset
18
Updating a Dataset
• Changes to data in the dataset do not
affect the database unless an explicit
operation is executed
• Via the data adapter, you can make the
changes in the dataset and then write the
changes back to the data source
• Initialization code
19
Updating a Dataset
• Adding a record
– Create an empty row that has the same fields
as in the table to be modified
– Enter data into the fields of the new row
– Add the new row to the table in the dataset
– Save the updated table back to the data
source
20
Updating a Datase
• Delete a record
– RemoveAt method
– Ensure that the user really wants to proceed
with the deletion
– Update method
• Editing a record
– Update method
– Many safeguards are needed
21
Creating Datasets Using SQL
• Structured query: a statement written
according to the rules of a language called
Structured Query Language (SQL), that
uniquely identifies a set of records from
one or more tables
• Basic syntax of an SQL SELECT
command (or a structured query)
– SELECT field(s) FROM table(s) [WHERE
condition(s)] [ORDER BY field(s)]
22
Creating Datasets Using SQL
• SELECT clause specifies the field values
that will be returned by the query
– SELECT * specifies that all fields are to be
obtained
• FROM clause specifies the table or tables
where records will be searched
• WHERE clause is used to place any
restrictions on the data to be selected
• ORDER BY clause is used if the selected
information is to be presented in a
23
specified order
DataGrid Control
• Used to display and modify one or more
database tables
• To create a DataGrid on a form
– Click on the DataGrid control in the toolbox
and then draw it on the Form, or
– Double-click on the tool and resize it on the
Form
• To associate a DataGrid control with a
table in an existing dataset
– Set the DataSource property to the name of
the table
24
DataGrid Control
DataGrid Control Initially placed on a Form
25
Common Programming Errors
and Problems
• Not saving the last edit performed on a dataset
• Forgetting that changes to the dataset are not
automatically reflected in the data source
• Forgetting to put quotes around the string in a
WHERE clause of an SQL statement that is
equal to a field
• Forgetting that the Position property starts at
zero and that the first record in a dataset is at
position zero, not one
26