Database ManagementReview for Final (Part 1)

School of BusinessEastern Illinois University

© Abdou Illia, Spring 2003

(Week 15, Wednesday 4/30/2003)

2What is a Database ?

Database: Collection of information stored in tables

Example: BIBLIO.MDB

Au_ID Author Year Born

Authors table (6246 Records, 3 Fields)

PubID Name Company Fax Comments

Publishers table (727 Records, 10 Fields)

Au_IDISBN

Title Author table (16056 Records, 2 Fields)

3Table, Field, Record

Authors Table

Au_ID Author Year_Born

A001 Jacobs, Russell 1945

A002 Metzger, Philip W. 1961

A003 Sydow, Dan Parks 1948

: : :

: : :

Field Record

4VB and Database Management

Two tools in VB 6.0 to manage databases – Activex Data Object (ADO)

– Data Access Object (DAO)

ADO control should be added to the toolbox (Project/Components… and check Microsoft ADO Data Control)

ADO and DAO controls can be used to:– Connect to a database.– Open a specified database table.– Create a virtual table based on a database query.– Pass database fields to other Visual Basic tools, for display or editing.

Such tools are bound tools (controls), or data-aware.– Add new records or update a database.

5DAO control

Common properties:– DatabaseName Used to set the name and location of database– RecordSource Used to set specific table in the database– EOF End of File– BOF Beginning of File– RecordCount Number of records

Examples:

Name: datBiblioDatabaseSource: C:\Program Files\Microsoft Visual Studio\VB98\BIBLIO.MDBRecordSource: Titles

6Bounding Text boxes to DAO control

Text boxes are said data-aware because they can be bound to DAO controls and access their data

Two Text boxes properties are used to bound them to DAO controls: – DataSource Used to set the DAO control from which data is read– DataField Used to set the field of the table from which data

is read

Examples:

Name: txtTitleDataSource: datBiblioDataField: Title

Name: TxtYearDataSource: datBiblioDataField: Year_Published

7Exercise

Create the following user-interface with one DAO control and two text boxes so that data in the table Titles from the database BIBLIO.MDB (found in the main VB directory).

Name: txtTitleDataSource: datBiblioDataField: Title

Name: TxtYearDataSource: datBiblioDataField: Year_Published

Name: datBiblioDatabaseSource: C:\Program Files\Microsoft Visual Studio\VB98\BIBLIO.MDBRecordSource: Titles

8ADO control: Methods

Common methods used:– MoveFirst Move to the 1st record and make it the current record– MoveLast Move to the last record and make it the current record– MoveNext Move to the next record and make it the current record– MovePrevious Move to the previous record and make it the current record– Recordset Used to refer to the content of the table in RecordSource

Recordset.Fields(“FieldName") Recordset.Fields(" FieldName").Value

Example:

datBiblio.Recordset.MoveLast ' Needed to set the value of RecordCount

datBiblio.Recordset.MoveFirst

For i = 0 To datBiblio.Recordset.RecordCount

datBiblio.Recordset.MoveNext

Next i

9ADO control: Examples

Example 1 : If EOF is reached, move to the previous record

If datBiblio.Recordset.EOF

datBiblio.Recordset.MovePrevious

End If

Example 2 : Delete the current record

datBiblio.Recordset.Delete

Example 3 : Use datBiblio to add items do a list box

To be done in class

Review For Final (Part 1)

Setting properties, Assignment statements

12Statements for setting properties

General rule:

ObjectNane.Property = Value

Where ObjectName is the name of the Object

Property is one of the properties of the object

Value is a valid setting for Property

Such statements are called Assignment statements

13Setting colors

At design time– Colors are selected from the palette (in Properties Win.)

When writing code– 8 most common colors can be assigned with the following

color constants:

vbBlack vbRed vbGreenvbYellow

vbBlue vbMagneta vbCyan vbWhite

Example: txtBox.ForeColor = vbGreen

14Assigning Font settings

At design time– Font settings are assigned from the palette (in Properties

Win.)

When writing code– Font settings can be assigned using statements like:

txtBox.Font.Name = “Courier”

txtBox.Font.Name = “Arial”

txtBox.Font.Size = 18

lblOne.Font.Italic = True

15Exercises

Exercises 19-32, page 68Write a line (or lines) of code to carry out the following:

Display “The stuff that dreams are made of.” in red letters in txtBox

txtBox.ForeColor = vbRed

txtBox.Text = “The stuff that dreams are made of.”

Display “Life is like a box of chocolates.” in Courier font in txtBox

txtBox.Text = “Life is like a box of chocolates.”

txtBox.Font.Name = “Courier”

16Exercises

Delete the content of txtBox

txtBox.Text = “”

Delete the content of lblTwo

lblTwo.Caption = “”

17Exercises

Make lblTwo disappear

lblTwo.Visible = False

Remove the border from lblTwo

lblTwo.BorderStyle = 0

Give picBox a blue background

picBox.BackColor = vbBlue

18Exercises

Place a bold red “Hello” in lblTwo

lblTwo.Font.Bold = True

lblTwo.ForeColor = vbRed

lblTwo.Text = “Hello”

19Exercises

Place a bold italic “Hello” in txtBox

txtBox.Font.Bold = True

txtBox.Font.Italic = True

txtBox.Caption = “Hello”

Make picBox disappear

picBox.Visible = False

20Exercises

Give the focus to cmdButtom

cmdButton.SetFocus

Remove the border from picBox

picBox.BorderStyle = 0

21Exercises

Place a border arround lblTwo and center its content

lblTwo.BorderStyle = 1

lblTwo.Alignment = 2

Give the focus to txtBoxTwo

txtBoxTwo.SetFocus

Built-in Functions

23Numeric Functions

Rnd Returns a number between 0 and 1.(excluding 1)

Sqr(n) Returns the square root of a number.

Round(n,r) The number n is rounded to r decimalplaces.

Int(n) Returns the largest integer less thanor equal to a number

24Numeric Functions

Examples

Sqr (9) is 3 Int(2.7) is 2 Round(2.7) is 3

Sqr (0) is 0 Int(3) is 3 Round(2.317,2) is 2.32

Sqr (2) is 1.4142 Int(-2.7) is -3 Round(2.317,1) is 2.3

Private Sub cmdEvaluate_Click() Dim n As Single, root As Single ' Evaluate functions at a variable picResults.Cls n = 6.76 root = Sqr(n) picResults.Print root; Int(n); Round(n, 1)

End Sub

25String Functions

Left (“String”, n) Returns a string containing a specified number of characters,

starting at the beginning of the “String”.

Right (“String”, n) Returns a string containing a specified number of

characters from the end of the “String”.

Mid (“String”, m, n) Returns a string containing a specified number of characters starting at the position indicated by the first number and continuing for the length specified by the second number

UCase (“String”) Converts any lowercase letters in string to uppercase

LCase (“String”) Converts any uppercase letters in string to lowercase

InStr (“Str1”, ”Str2“) Searches for the first occurrence of one string in another and gives the position at which the string is found

Len (“String”) Returns the number of characters in the string.

Trim (“ String ”) Returns “String” with leading and trailing spaces removed.

26String Functions

ExamplesLeft (“fanatic”, 3) is “fan” Right (“fanatic”, 3) is “tic” Mid (“fanatic”,5,1) is “t”

UCase(“Disk”) is “DISK” LCase(“Disk”) is “disk” Trim(“-12 “) is “-12”

27Format Function

The format functions provide detailed control of how numbers, dates, and strings are displayed.

Example:

FormatNumber (12345.678, 1) 12,345.6FormatCurrency (12345.678, 2) $12,345.68FormatPercent (.185, 2) 18.50%FormatNumber (1 + Sqr(2), 3) 2.414FormatDateTime(“9-15-99”, vbLongDate) Wednesday, September 15, 1999

Format(1234567890, “@@@@@@@@@@”) 1234567890Format(FormatNumber(1234.5), “@@@@@@@@@@”) 1,234.50

28Exercises

1. Given the data in the string variable y shown below, which of the following statements will assign the value ALL to the string variable x?

y = "WHEN ALL ELSE FAILS, READ THE DIRECTIONS“

(A) x = Mid(y, 6, 3)(B) x = Left(y, 3)(C) x = Middle(y, 6, 3)(D) x = Right(y, 8)

29Exercises

2. What will be displayed when the following program is executed?Dim a As String, b As String, c As Stringa = "THE WHOLE"b = "PART"c = Mid(a, Sqr(4), Len(b))picBox.Print c

(A) THE WHOLE PART(B) 6(C) HE W(D) HOLE(E) None of the above

30Exercises

3. What will be the output of the following statement?picBox.Print FormatCurrency(1234.567,2)

(A) $1234.567(B) 1,234.57(C) $1234.57(D) $1,234.57

31Exercises

4. What will be the output of the following lines?Dim alphabet As String, soup As Stringalphabet = "abcdefghijklmnopqrstuvwxyz"soup = UCase(alphabet)picBox.Print Left(alphabet, 5); Left(soup, 5)

(A) abcdeABCDE(B) ABCDEABCDE(C) eE(D) EE

32Exercises

5. What output is generated by the following statements (show the output EXACTLY as it would appear)?(A) picBox.Print Sqr(3^2 + 4^2)

(B) picBox.Print Mid("Milkshake", 5, 5)

(C) picBox.Print UCase("123jump")