21 web applications writing data to databases using asp
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21 – Web applications: Writing data to Databases using ASP. 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:

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session aims objectives
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
searching for data
Searching for Data
  • Recordset methods
    • Find: searches for the next record to match given criteria string:
      • e.g. "Name = \'Smith\' "( " are for VB string)( \' are for database string)
example person v1 specification
Example: Person v1 (Specification)
  • User requirement:
    • Display person’s details from database online, and be able to move to next and previous person (record)
  • Problem:
    • Can’t use .MoveNext and .MovePrev recordset methods:record set does not persist between pages
example person v1 html
Example: Person v1 (html)

Self post

<html>

<head>

<title>Person\'s Details</title>

</head>

<body>

<p><center><b><font size=+2>Person\'s Details</font></b></center>

<%

\' ASP code will go here (next slide).

%>

<form action="Person.aspx" method=post>

<input name="btnPrev" type="submit" value="Previous">

<input name="btnNext" type="submit" value="Next">

</form>

</body>

</html>

example person v1 asp
Example: Person v1 (ASP)

Button value empty unless

button was pressed

Use session variable to

record current position in db

<%

Const adOpenDynamic = 3

Const cs = "…"

Dim rs

rs = CreateObject("ADODB.Recordset")

rs.Open("Person", cs, adOpenDynamic)

If Session("curID") <> "" Then

rs.Find("[ID] = " & Session("curID"))

If Request.Form("btnPrev") <> "" Then

rs.MovePrevious()

ElseIf Request.Form("btnNext") <> "" Then

rs.MoveNext()

End If

End If

Session("curID") = rs.Fields("ID").Value

Response.Write(rs.Fields("Surname").Value & "<br>")

Response.Write(rs.Fields("Forenames").Value)

rs.Close()

rs = Nothing

%>

example person v2 specification
Example: Person v2 (Specification)
  • User requirement:
    • Display person’s details from database online, and be able to move to next and previous person (record)
    • Change surname and save to database
database permissions 1
Database Permissions 1
  • 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 2000)
database permissions 2
Database Permissions 2
  • Click Security tab
  • Click Add button
database permissions 3
Database Permissions 3
  • Select Internet Guest Account IUSR_ … ClickAddbuttonClickOKbutton
database permissions 4
Database Permissions 4
  • Select InternetGuest Account
  • Ensure writeaccess is on
writing data to a database
Writing data to a database
  • create recordset
  • open recordset
    • dynamic cursor (3), pessimistic locking (3)
  • to add a record
    • use to AddNew method rs.AddNew
  • to delete a record
    • use the Delete method rs.Delete
  • to change existing data
    • assign a new value to fieldsrs.Fields("Surname").Value = "Fred"
changing data
Changing Data
  • Recordset methods
    • AddNew: inserts a new record and makes it current
    • Update: sends changes back to DB
    • Delete: deletes currently selected record
example person v2 html
Example: Person v2 (html)

<html>

<head>

<title>Person\'s Details</title>

</head>

<body>

<p><center><b><font size=+2>Person\'s Details</font></b></center>

<%

\' ASP code will go here (next slide).

%>

<form name="frmPerson" action="PersonEdit.aspx" method=post>

Surname: <input name="txtSurname" type="text"value="<%=Surname%>"><br>

<input name="btnPrev" type="submit" value="Previous">

<input name="btnSave" type="submit" value="Save">

<input name="btnNext" type="submit" value="Next">

</form>

</body>

</html>

PersonEdit.aspx

example person v2 asp
Example: Person v2 (ASP)

<%

Const cs = "…"

Dim rs

Dim Surname

rs = CreateObject("ADODB.Recordset")

rs.Open("Person", cs, 3, 3)

If Session("curID") <> "" Then

rs.Find("[ID] = " & Session("curID"))

If Request.Form("btnPrev") <> "" Then

rs.MovePrevious()

ElseIf Request.Form("btnNext") <> "" Then

rs.MoveNext()

ElseIf Request.Form("btnSave") <> "" Then

rs.Fields("Surname") = Request.Form("txtSurname")

rs.Update()

End If

End If

Session("curID") = rs.Fields("ID").Value

Surname = rs.Fields("Surname").Value

rs.Close()

rs = Nothing

%>

tutorial exercise person v1
Tutorial Exercise: Person v1
  • Task 1: Get the Person (v1) example from the lecture working.
  • Task 2: Modify your code, so that all fields are displayed.
  • Task 3: Modify your code, so that it does not generate an error when the user goes past the end or beginning of the recordset.
tutorial exercise person v2
Tutorial Exercise: Person v2
  • Task 1: Get the Person (v2) example from the lecture working.
  • Task 2: Modify your code, so that a line of text is displayed confirming that data has been saved.
tutorial example phone book
Tutorial Example: Phone Book
  • Task 1: Get the Phone Book example from the lecture working.
  • Task 2: Add a button on your page that jumps to another page, which allows a new record to be added.
  • Task 3: Modify your code, so that each line (record) has a link leading to another page that allows the data to be edited.
  • Task 4: Modify your code, so that each line (record) has a link leading to another page that allows the record to be deleted.
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