Download Lecture 4.13.2011 - Databases Part 3

Programming in Visual Basic 2010:
The Very Beginner’s Guide
Chapter 14.3
LINQ to SQL
Databases – Part 3
by Jim McKeown
Customer Queries
Sometimes there’s just too much data
• Queries look through a database and retrieve
data that matches the search criteria
• Queries find records that match the search,
display selected fields in the results and order
the records for easy reference
• Use a DataGridView to demonstrate a query
Query
•
2
search or searches in a database;
return specified fields from selected records and
display them in a specific order
Database File for this Part
We need the Customers database file
See my web page.
Download and open and look at it. Close it.
3
Customer Queries
Create a new form
Name the controls
Add a DataGridView (I used a form)
4
Tasks – Build the Connections, etc.
See grid in book and create form from it, if you wish.
Or use the DataGridView control from the toolbox in lieu of
the form and controls we’re used to.
If you use controls, name Controls and Labels,…
Either will be okay.
Electing to do the form is a bit more work; when electing
the datagridview, some things are done for you…
The slides ahead are for Forms:
5
Add Binding Source from Toolbox (Category: Data)
Name it bdsCustomer in Name Property
Add DataSource property
via drop down….
Goto next slide
(except this one)
If using DataGridView in lieu of Form
6
If using DataGridView in lieu of form, there are a few
differences. Here are a few…
select DataGridView control.
Click on play
Choose Data Source
can select WagesDataSetBinding
Links WagesDataSet and
WagesDataSetBinding in component tray
Select WagesDataSetBindingSource
See properties DataSource (linked to WagesDataSet)
Select DataMember; select tblWages
Note: grid modified and has fields. Expand.
Fill form space up with grid…
Tasks
Add Project Data Source items…
Database, dataset, New Connection, Change,
(Microsoft Access Database File), Browse for
Database File (from desktop), Select
Customers.mdb, (book says Wages. Wrong)
Test Connection, OK
Next, Yes, Next,
Goto next slide
7
Tasks
Step 10 in book, p. 588
Select Database Objects for the Data Set.
we do this by expanding the Tables Checkbox
click on tblCustomers.
Leave checked.
Finish
Component Tray now includes A Customers Data
Set
8
Tasks
Select DataMember property of binding source
(bdsCustomer) and set to tblCustomers.
Adds TBLCustomersTable Adaptor to
Component tray.
Save Project.
Onto Step 13 in book…
9
Tasks
Bind the Controls to the Dataset (if using
controls / form).
For each control, Go to DataBindings in property
window, Text properties, bdsCustomer, and
associate controls to dataset objects.
10
Tasks
Add Binding Navigator
drag from toolbox to top of form
Name it bdsCustomers via property window
Link your binding navigator to your data by
changing BindingSource property of the
binding navigator to bdsCustomer (drop
down)
Run your program!!
11
On to Customer Queries
Select TblCustomersTableAdapter in component
tray.
Select Add Query... at the bottom of the Properties
window
Search Criteria Builder wizard displays
Select a New query name: and enter Outdoors to
build a query of customers interested in the
outdoors (see next slide)
12
Query Wizard looks like:
Customers
Search
Criteria
Builder
Added query
name
13
Customer Queries
Select Query Builder button to open the Query
Builder dialog (three slides down)
Top section has the fields listed for tblCustomers
and all fields are selected
Leave all the fields selected
All fields must be selected when using the
DataGridView
14
Customer Queries
Second section has a list of the fields and the
search criteria for it (two slides down)
Build your query in this section
Scroll down to the Interests field
Change the Filter to = ‘Outdoors’
Modifies a query template (next slide) that looks
through all the records and returns those with
Outdoors as an Interest
And adds the query being built in the third section
15 See SQL next slide:
Customer Queries
Third section now reads
SELECT
ID, LastName, FirstName, CustNum, Address,
City, State, Zip, Since, [Last], Preferred,
AcctBalance, Interests
FROM
tblCustomers
WHERE
(Interests = 'Outdoors') ADDED THE Where!
16
WHERE clause added to the SQL statement being
build
Statement says to select all fields from
tblCustomers and only those records where
‘Outdoors’ is in the Interests field
Customer Queries
Customers
Query
Builder
17
Customer Queries
Select OK to close the Query Builder (last slide)
Select OK to close the Search Criteria Builder and
create your query (slide not shown)
• ToolStrip named OutdoorsToolStrip is added to
component tray and thus your query is added!
• underneath Binding Navigator
Run program; all records available as output
Select Outdoors runs the query and it displays
only those records with Outdoors listed in the
Interests field
18
Customer Queries
Note the Code added to the click event for the
Outdoors button on the ToolStrip
Try
Me.TblCustomersTableAdapter.Outdoors(Me.CustomersDa
taSet.tblCustomers)
Catch ex As System.Exception
System.Windows.Forms.MessageBox.Show(ex.Message)
End Try
19
Query: Select All Records. (new)
Select TblCustomersTableAdapter in component tray
Select Add Query... bottom of the Properties window
Displays Search Criteria Builder wizard
Data source table already set
Select a New query name: (I named it AllQuery) and
Select Query Builder Button.
(Want all, so no changes)
Select OK for Query Builder (see window title too)
20 Select OK for Search Criteria Builder (see window title)
Query: AllQuery
SQL stays the same.
SELECT
ID, LastName, FirstName, CustNum, Address,
City, State, Zip, Since, [Last], Preferred,
AcctBalance, Interests
FROM
tblCustomers
ToolStrip named All added to the component try and
underneath Binding Navigator strip
21
Run the program
Click Outdoors to run that query and it displays only those
records in the DataGridView
Click All to display all the records in your view.
Query: AllQuery
Code added to the click event for the All button in
the new ToolStrip
Also added another subroutine in the code window
for this query: Private Sub
AllQueryToolStripButton_Click….
Try
Me.TblCustomersTableAdapter.All(Me.CustomersDataSet
.tblCustomers)
Catch ex As System.Exception
22
System.Windows.Forms.MessageBox.Show(ex.Message)
End Try
More
If you want to play with these, you can get rid of a
set of query toolstrips.
See book.
23
Data Base Terminology - Important
When a DataSet is created it generates an .xsd file
View it by selecting the TableAdapter and Edit Queries in
the DataSet Designer at the bottom of the Properties
window
Contains the XML schema
XML (Extensible Markup Language):
Is a specification for creating content and structure for
data;
24
XML is an open standard specification widely used as a
specification language for data and the web
Customer Queries
These documents define and validate the content
and structure of your data
Use to exchange data between applications
Schema
a diagram or plan detailing the structure of your
content; for VB, it contains the structure for your
DataSet
25
Customer Queries
Customers
DataSet1
Existing Queries
26
VB Quiz 03
What happens if you don't select all the fields for a query?
An Exception will be generated.
What makes the Query Builder useful?
You don’t have to know SQL. But this is limiting…
How were the records sorted in the Payable query?
Last Name
What SQL code was needed to do it?
Ordered by…
27
Potential Problems
Your program won’t work if the database is corrupt
Database file cannot be in use by another program
Don’t delete or change code that’s automatically
generated
Bind your DataSet to a DataGridView or to
individual controls such as a TextBox or Label
Include a BindingNavigator so you can move
between records
Be careful when deleting controls from the
component tray and Solution Explorer
28
On Your Own
Take a look at Appendix G -- Structured Query
Language (SQL) Basics
Add queries to the Customer program
Customers in your state
Customers without Preferred status
Customers name Ecks, Ray
Customers since 2008
29
On Your Own
Create a program with the Customers file that
displays data in TextBoxes and CheckBoxes
Add controls and code to allow the user to update
the database
30
Part 5; Project 4. 50 points
Create a program with the KidsFirst file that
displays data in a DataGridView
Add queries to find
all students in Miss Brooks class
all students without a pet (look for ‘none’)
all seven-year-old students
all seven-year-old students in Mr. Moore’s class
all students in order by LastName
all students in descending order by Locker
31
If you are smart….
You will go over the Review questions, the terms,
the multiple choice questions, etc. at the end of
the chapter!
32
Summary
Visual Basic has controls that can link it to a
database
Chapter contains tutorials to demonstrate how to
connect to an Access file and manipulate records
in a file
Database controls were introduced
Simple SQL examples were introduced
33