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Count Records by Juan
Llibre, Charles Carroll
This script counts the records in a database. Many
people who attempt to use the .recordcount property have the value -1 returned
to them. In a nutshell, -1 means "I don't know how many records this
query/table contains". It happens since the default cursor type is
AdOpenforwardonly (see below for explanation of all cursor types).
Here is the script that counts the query results
and WILL NOT return -1:
filename=/learn/test/dbcount.asp
<head><html>
<TITLE>dbcount.asp</TITLE>
</head><body bgcolor="#FFFFFF">
<!--#INCLUDE VIRTUAL="/ADOVBS.INC" -->
<%
' change these for your site
connectme="DSN=Student;uid=student;pwd=magic"
sqltemp="select * from publishers where state='NY'"
set rstemp=Server.CreateObject("adodb.Recordset")
rstemp.open sqltemp, connectme, adopenstatic
howmanyrecs=rstemp.recordcount
response.write howmanyrecs & " records in<br>" & sqltemp
rstemp.close
set rstemp=nothing
%>
</body></html>
The critical
part here is having a cursor type that supports it (Adopenforward only is the
default cursor type and it does NOT support counting records) and including adovbs.inc to
define the cursor types. The file adovbs.inc can be obtained from http://www.learnasp.com/adovbs.inc
If you open the database and are able to obtain an accurate record
count is by nature a slower connection; it is a burden on a recordset that it
must know exact record counts upon demand. The additional overhead and
limitations of a adopendynamic or adopenstatic cursor may be a glacially
slow way to
retrieve the data even though they count accurately. If
you must count AND retrieve, you can't go wrong using GetRows (see http://www.learnasp.com/freebook/asp/dbtablegetrow.aspx)
because:
- GetRows can count with any cursor type and is
very fast at retrieving and counting!
- is much faster and conserves server resources,
see:
/advice/whygetrows.asp
Here is a description of the significance of each
cursor type:
Adopenstatic cursor
The data is dead. If you retrieve a million records for example at
9:00am and it takes 6 minutes to read the data, at the 6th minute you will not
be retrieving fresh or recently added data. It is like a snapshot of the data.
Recordsets opened this way WILL contain an accurate recordcount.
Adopenforwardonly cursor (the
default)
The data is alive but you can only move forward. Attempts to move
backward or to specific record numbers will fail.. Recordsets opened this way WILL
NOT contain an accurate recordcount, instead returning -1.
Adopenkeyset cursor
The data is alive and any record read will be the
most recent data. f you retrieve a million records for example at 9:00am
and it takes 6 minutes to read the data, at the 6th minute you will still be
retrieving fresh data but NOT data added or deleted since 9am. Recordsets opened
this way WILL NOT contain an accurate recordcount, instead returning -1.
Adopendynamic cursor
The data is alive and additions will be noticed. If you retrieve a
million records for example at 9:00am and it takes 6 minutes to read the data,
at the 6th minute you will still be retrieving fresh data and records added to
the end of the data. Recordsets opened this way WILL contain an
accurate recordcount.
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There are many worthy charities!!. But perhaps help starving children in Africa or South America AND help Charles too.
a $5 tip buys him lunch at McDonalds,
a $20 tip buys his kid Hitoshi a new computer game,
a $39 tip buys his daughter Michiko a few nice outfits.
See our donor list.
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