23 – web applications: writing data to databases using asp
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23 – Web applications: Writing data to Databases using ASP. Questions: HTML in VB. Are these correct (assume variables and fields exist)? f = f + rs.Fields(" Description ").value h = h + rs.Fields(" Name ").value a = "" + a "" html = html + - PowerPoint PPT PresentationTRANSCRIPT
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23 – Web applications:Writing data to Databases
using ASP
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Questions: HTML in VB• Are these correct (assume variables and
fields exist)?
f = f + rs.Fields("Description").value
h = h + rs.Fields("<br />Name").value
a = "<p>" + a "</p>"
html = html + <img src=face.gif />
h = "<table>" + h + "</table>"
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Questions: Databases• How many primary keys?• How many foreign keys?
32
PlantPlantID EnglishName ScientificName Price Toxic FileName
1 Foxglove Digitalis purpurea 2.5 TRUE Foxglove.jpg2 Daisy Bellis perennis 0.45 FALSE Daisy.jpg3 Hemlock Conium maculatum 8.79 TRUE Hemlock.jpg4 Marsh Mallow Althaea officinalis 3.25 FALSE MarshMallow.jpg5 Lords-and-Ladies Arum maculatum 2.25 TRUE Lords.jpg6 Wild Carrot Daucus carota 1.25 FALSE WildCarrot.jpg7 Bluebell Hyacinthoides non-scripta 1.8 FALSE Bluebell.jpg8 Common Poppy Papaver rhoeas 1.28 FALSE Poppy.jpg
OrderOrderID CustID PlantID Quantity Date Current
1 1 7 10 14-Mar-06 TRUE2 2 5 2 14-Mar-06 TRUE3 1 3 1 14-Mar-06 FALSE5 2 4 4 14-Mar-06 FALSE
46 1 2 9 09-Jun-06 FALSE
CustomerCustID Surname Forenames email Password
1 Dixon Mark [email protected] a2 Jones Sally [email protected] sally
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Session Aims & Objectives• Aims
– To introduce the fundamental ideas involved in using server-side code to write data to databases
• Objectives,by end of this week’s sessions, you should be able to:
– create an ASP web page that allows the user to store data in database
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Example: Person v1 (Specification)
• User requirement:– Display people's details from database online– need 2 pages:
smithjonesdixon
list of people
jonessally
person's details
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Example: PeopleList.aspx v1<script language="VB" runat="server"> Sub Page_Load() Const cs = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\People.mdb;" Dim rs As Object Dim s As String rs = CreateObject("ADODB.Recordset") rs.Open("Person", cs) s = "" Do Until rs.EOF() s = s & rs.Fields("Surname").Value & "<br />" rs.MoveNext() Loop parData.InnerHtml = s rs.Close() rs = Nothing End Sub</script>
<html> <head><title></title></head> <body> <p id="parData" runat="server"></p> </body></html>
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Example: PeopleList.aspx v2<script language="VB" runat="server"> Sub Page_Load() Const cs = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\People.mdb;" Dim rs As Object Dim s As String rs = CreateObject("ADODB.Recordset") rs.Open("Person", cs) s = "" Do Until rs.EOF() s = s & "<a href='Person.aspx?id=" & rs.Fields("ID").Value & "'>" s = s & rs.Fields("Surname").Value & "</a><br />" rs.MoveNext() Loop parData.InnerHtml = s rs.Close() rs = Nothing End Sub</script>
<html> <head><title></title></head> <body> <p id="parData" runat="server"></p> </body></html>
now links
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Example: Person.aspx v2<script language="VB" runat="server"> Sub Page_Load() Const cs = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\People.mdb;" Dim sql As String Dim rs As Object Dim s As String sql = "SELECT * FROM Person WHERE id=" & Request.QueryString("id") rs = CreateObject("ADODB.Recordset") rs.Open(sql, cs) s = "" If Not rs.EOF() Then txtSurname.Value = rs.Fields("Surname").Value End If rs.Close() rs = Nothing End Sub</script>
<html> <head><title></title></head> <body> <a href="PeopleList.aspx">Back to People List</a><br /> <form runat="server"> Surname: <input id="txtSurname" runat="server" /><br /> <input id="btnSave" type="submit" value="Save" runat="server" /> </form> </body></html>
reads querystring(from previous page)
displays data forselected record only
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Example: Person v2 (Specification)
• User requirement:Display person’s details from database online
– Change surname and save to database
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Database Permissions 1• Windows Explorer
– Tools– Folder Options– View Tab
• Need to turn'simple file sharing' off(as this disables the security tab in file properties)
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Database Permissions 2• In order for ASP to
write to a database– Need to give write
access to Internet Guest Account for database file (People.mdb)
• Right-click on file in Windows Explorer(the following screens are for Windows XP)
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Database Permissions 3• Click Security tab
• Click Add button
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Database Permissions 4• Click Advanced
button
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• Select Internet Guest Account IUSR_ … ClickFind button
Clickuser
ClickOK button
Database Permissions 5
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Database Permissions 6• Select Internet
Guest Account
• Ensure writeaccess is on
• Repeat forASPNET account
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Changing Data• Recordset methods
– AddNew: inserts a new record and makes it current
– rs.Fields("FieldName").value = "Data"
– Update: sends changes back to DB
– Delete: deletes currently selected record
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Writing data to a database• create recordset• open recordset
– dynamic cursor (3), pessimistic locking (3)
• to add a record– use to AddNew methodrs.AddNew
• to delete a record– use the Delete method rs.Delete
• to change existing data– assign a new value to fields
rs.Fields("Surname").Value = "Fred"
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Example: Person.aspx v3<script language="VB" runat="server"> Sub Page_Load() Const cs = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\People.mdb;" Dim sql As String Dim rs As Object Dim s As String sql = "SELECT * FROM Person WHERE id=" & Request.QueryString("id") rs = CreateObject("ADODB.Recordset") rs.Open(sql, cs, 3, 3) s = "" If Not rs.EOF() Then If Request.Form("btnSave") > "" Then rs.Fields("Surname").Value = txtSurname.Value rs.Update() End If txtSurname.Value = rs.Fields("Surname").Value End If rs.Close() rs = Nothing End Sub</script>
<html> <head><title></title></head> <body> <a href="PeopleList.aspx">Back to People List</a><br /> <form runat="server"> Surname: <input id="txtSurname" runat="server" /><br /> <input id="btnSave" type="submit" value="Save" runat="server" /> </form> </body></html>
Save button works now
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Tutorial Exercise: Person• Task 1: Get the Person (v1) example from the lecture
working.• Task 2: Modify your code, so that forename is displayed as
well as surname (use a table).• Task 3: Get the Person (v2 and v3) example from the
lecture working.• Task 3: Modify your code, so that a line of text is displayed
confirming that data has been saved.• Task 4: Modify your code, so that an add button is
included, which allows a new record to be added.• Task 5: Modify your code, so that a delete button is
included, which allows the current record to be deleted.