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Wednesday 25 February 2015

ADO Display

The most common way to display data from a recordset, is to display the data in an HTML table. 

Display the Field Names and Field Values

We have a database named "Northwind" and we want to display the data from the "Customers" table (remember to save the file with an .asp extension):

Example

<html>
<body>

<%
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open "c:/webdata/northwind.mdb"

set rs = Server.CreateObject("ADODB.recordset")
rs.Open "SELECT * FROM Customers", conn

do until rs.EOF
  for each x in rs.Fields
    Response.Write(x.name)
    Response.Write(" = ")
    Response.Write(x.value & "<br>")
  next
  Response.Write("<br>")
  rs.MoveNext
loop

rs.close
conn.close
%>

</body>
</html>


Display the Field Names and Field Values in an HTML Table

We can also display the data from the "Customers" table inside an HTML table with the following lines (remember to save the file with an .asp extension):

Example

<html>
<body>

<%
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open "c:/webdata/northwind.mdb"

set rs = Server.CreateObject("ADODB.recordset")
rs.Open "SELECT Companyname, Contactname FROM Customers", conn
%>

<table border="1" width="100%">
<%do until rs.EOF%>
  <tr>
  <%for each x in rs.Fields%>
    <td><%Response.Write(x.value)%></td>
  <%next
  rs.MoveNext%>
  </tr>
<%loop
rs.close
conn.close
%>
</table>

</body>
</html>


Add Headers to the HTML Table

We want to add headers to the HTML table to make it more readable (remember to save the file with an .asp extension):

Example

<html>
<body>

<%
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open "c:/webdata/northwind.mdb"

set rs = Server.CreateObject("ADODB.recordset")
sql="SELECT Companyname, Contactname FROM Customers"
rs.Open sql, conn
%>

<table border="1" width="100%">
  <tr>
  <%for each x in rs.Fields
    response.write("<th>" & x.name & "</th>")
  next%>
  </tr>
  <%do until rs.EOF%>
    <tr>
    <%for each x in rs.Fields%>
      <td><%Response.Write(x.value)%></td>
    <%next
    rs.MoveNext%>
    </tr>
  <%loop
  rs.close
  conn.close
  %>
</table>

</body>
</html>

ADO Recordset

To be able to read database data, the data must first be loaded into a recordset. 

Create an ADO Table Recordset

After an ADO Database Connection has been created, as demonstrated in the previous chapter, it is possible to create an ADO Recordset.  
Suppose we have a database named "Northwind", we can get access to the "Customers" table inside the database with the following lines:
<%
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open "c:/webdata/northwind.mdb"

set rs=Server.CreateObject("ADODB.recordset")
rs.Open "Customers", conn
%>

Create an ADO SQL Recordset

We can also get access to the data in the "Customers" table using SQL:
<%
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open "c:/webdata/northwind.mdb"

set rs=Server.CreateObject("ADODB.recordset")
rs.Open "Select * from Customers", conn
%>

Extract Data from the Recordset

After a recordset is opened, we can extract data from recordset.  
Suppose we have a database named "Northwind", we can get access to the "Customers" table inside the database with the following lines:
<%
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open "c:/webdata/northwind.mdb"

set rs=Server.CreateObject("ADODB.recordset")
rs.Open "Select * from Customers", conn

for each x in rs.fields
  response.write(x.name)
  response.write(" = ")
  response.write(x.value)
next
%>

The ADO Recordset Object

The ADO Recordset object is used to hold a set of records from a database table. 

Introduction to ADO

What is ADO?

  • ADO is a Microsoft technology
  • ADO stands for ActiveX Data Objects
  • ADO is a Microsoft Active-X component
  • ADO is automatically installed with Microsoft IIS
  • ADO is a programming interface to access data in a database

Accessing a Database from an ASP Page

The common way to access a database from inside an ASP page is to:
  1. Create an ADO connection to a database
  2. Open the database connection
  3. Create an ADO recordset
  4. Open the recordset
  5. Extract the data you need from the recordset
  6. Close the recordset
  7. Close the connection
Before a database can be accessed from a web page, a database connection has to be established.

Create a DSN-less Database Connection

The easiest way to connect to a database is to use a DSN-less connection. A DSN-less connection can be used against any Microsoft Access database on your web site.
If you have a database called "northwind.mdb" located in a web directory like "c:/webdata/", you can connect to the database with the following ASP code:
<%
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open "c:/webdata/northwind.mdb"
%>
Note, from the example above, that you have to specify the Microsoft Access database driver (Provider) and the physical path to the database on your computer.

Create an ODBC Database Connection

If you have an ODBC database called "northwind" you can connect to the database with the following ASP code:
<%
set conn=Server.CreateObject("ADODB.Connection")
conn.Open "northwind"
%>
With an ODBC connection, you can connect to any database, on any computer in your network, as long as an ODBC connection is available.

An ODBC Connection to an MS Access Database

Here is how to create a connection to a MS Access Database: 
  1. Open the ODBC icon in your Control Panel.
  2. Choose the System DSN tab.
  3. Click on Add in the System DSN tab.
  4. Select the Microsoft Access Driver. Click Finish.
  5. In the next screen, click Select to locate the database.
  6. Give the database a Data Source Name (DSN).
  7. Click OK.
Note that this configuration has to be done on the computer where your web site is located. If you are running Personal Web Server (PWS) or Internet Information Server (IIS) on your own computer, the instructions above will work, but if your web site is located on a remote server, you have to have physical access to that server, or ask your web host to do this for you.