Transcript Judul - Binus Repository

Matakuliah
Tahun
Versi
: D0524 / Algoritma dan Pemrograman Komputer
: 2005
:
Pertemuan 09
Database
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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
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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
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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
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Introduction to Database
Related to Exactly One
Related to One or More
Related to Zero or One
Related to Zero or More
ERD Symbols
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Introduction to Database
Manajer
Departemen
Karyawan
Kendaraan
Operasional
Example of ER Diagram
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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
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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
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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
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Using ADO with Visual Basic
Data
Source
Connection
Data
Adapter
Dataset
Setting up Data Access in Visual Basic
Windows
Form
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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
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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
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Setting up a Data Adapter
First Screen of the Data Adapter Configuration Wizard
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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
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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
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Filling the Dataset
• The data adapter’s Fill method
– Used to fill the dataset at run-time
– DataAdaptername.Fill(DataSetName)
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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
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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
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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
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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
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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)]
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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
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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
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DataGrid Control
DataGrid Control Initially placed on a Form
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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
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