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The first few lines are the opening HTML tags for any page. There's no ASP

code within them. The ASP block begins with the statement,

Dim DB

which is a declaration of the variable that we're gonna use later on. The

second line,

Set DB = Server.CreateObject (“ADODB.Connection”)

does the following two things:

Firstly, the right-hand-side statement, Server.CreateObject() is used to

create an instance of a COM object which has the ProgID

ADODB.Connection. The Set Statement then assigns this reference to our

variable, DB. Now, we use the object just created to connect to the database

using a Connection String.

The string,

"PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA SOURCE=" +

“C:\Databases\Students.mdb”

is a string expression that tells our object where to locate the database, and

more importantly, what type the database is – whether it is an Access

database, or a Sybase database, or else, is it Oracle. (Please note that this is a

Connection String specific to Access 2000 databases. This example does not

use ODBC.)

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If the DB.Open statement succeeds without an error, we have a valid

connection to our database under consideration. Only after this can we begin

to use the database.

The immediate next lines,

Dim RS

Set RS = Server.CreateObject (“ADODB.Recordset”)

serve the same purpose as the lines for creating the ADODB.Connection

object. Only now we're creating an ADODB.Recordset!

Now,

RS.Open “SELECT * FROM Students”, DB

is perhaps the most important line of this example. Given an SQL statement,

this line executes the query, and assigns the records returned to our Recordset

object. The bare-minimum syntax, as you can see, is pretty straight-forward.

Of course, the Recordset.Open (...) method takes a couple of more

arguments, but they are optional, and would just complicate things at this

juncture.

Now, assuming that all the records we want are in our Recordset object, we

proceed to display it.

If RS.EOF And RS.BOF Then

Response.Write “There are 0 records.”

In any scenario where it is expected that no records might exist, this is an

important error check to be performed. In case your query returned no results,

the Recordset.BOF (beginning of file) & Recordset.EOF (end of file) are

both True at the same time. So you can easily write an If-statement to

perform a very basic error check. (If you don't do this now, you'll encounter

errors in the later part of the script. It's always wise to prevent rather than

cure errors.)

We shall look at the next few lines as a complete block and not as separate

lines of code.

Else

RS.MoveFirst

While Not RS.EOF

Response.Write RS.Fields (“FirstName”)

Response.Write RS.Fields (“LastName”)

Response.Write “<HR>”

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RS.MoveNext

Wend

End If

RS.MoveFirst is a method that moves the record pointer (for now, consider

this to be an imaginary structure that always points to the current record in the

Recordset) to the First record. By default, it may or may not be positioned

correctly, so it is imperative to position it before you begin any operations.

Then we have a While-loop that iterates through all the records contained in

the Recordset. The condition that we check is that RS.EOF should be False.

The moment it is True, it can be inferred that there are no more records to be

found.

RS.Fields(“FirstName”) retrieves the value of the “FirstName” field of

the current record. We use a Response.Write statement to write it out to the

page. Similarly, we write the RS.Fields (“LastName”) after the first name.

You may also use a shortcut syntax for this, which takes the form:

RS (”FirstName”)

After you're done displaying, you must advance the record pointer to the next

record, so you execute a RS.MoveNext. And that's all you wanted to do within

the loop, so you end the loop now. Just write Wend and the loop ends! And so

does our little example!

Moving on to complex queries

Queries are what get complex, not the method of accessing data! So no matter

what data you want, you use exactly the same syntax in your code. The only

thing that changes is the SQL statement, and perhaps, the fields that you

actually display on the page.

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