refer
url:http://www.4guysfromrolla.com/webtech/102999-1.shtmlWhile working on a web based competency-testing application I needed a way to return not just ONE random record but a group of random records. I searched the net high and low for a couple of months trying to find something that would allow me do this. I eventually hunkered down and came up with my own way of doing this.
First comes the SQL statement to return the set of records you will pick your Random records from:
<% strConnection="driver={Microsoft Access Driver (*.mdb)};dbq=" & server.mappath("/testdb.mdb") strSQL = "SELECT id FROM tblQuestions" set objConn = Server.CreateObject("ADODB.Connection") Set objRst = Server.CreateObject("ADODB.Recordset") objConn.Open strConnection set objRst.ActiveConnection = objConn objRst.LockType = adLockOptimistic objRst.CursorType = adOpenKeySet objRst.Open strSQL%> |
Next, set the upper limit of the Randomize function by setting the variable rndMax equal to the RecordCount.
<% objRst.MoveLast cnt = objRst.RecordCount cnt1 = cnt rndMax = cnt%> |
Next, set the number of records returned to either the number of questions they asked for or equal to the RecordCount.
<% If CInt(Request.Form("maxNumber")) < cnt Then cnt1 = CInt(Request.Form("maxNumber")) End If%> |
Now we want to return a Random number. Check if the variable
str1 already contains that number. If so then that number is skipped and it loops again returning another Random record number. This ensures that
no values are repeated. If not then plug that number into the
str1 variable so we will know that that number has already been used the next time through the loop. If the random number is not contained within the
str1 variable then the value of the
ID field is returned and plugged into the
str1 variable. This loops until the appropriate number of values have been plugged into the
str1 variable.
<% str = "," str1 = "," Do Until cnt1 = 0 Randomize RndNumber = Int(Rnd * rndMax) If (InStr(1, str1, "," & RndNumber & "," ) = 0) Then str1 = str1 & RndNumber & "," cnt1 = cnt1 - 1 objRst.MoveFirst objRst.Move RndNumber str = str & objRst("id") & "," End If Loop%> |
Now we have a variable, (str), that contains a comma-delimited list of values from the
ID field. Now, just reference the comma- delimited string contained within the
str1 variable in your SQL statement:
<% sql = "SELECT * FROM tblQuestions WHERE (((InStr(1,'" & str & "',(',' & [id] & ',')))<>0)) "%> |
This will return your Random set of records!
Try out the demo! Here's the whole thing: <!--Generate a random recordset from an Access database--><!--#include virtual="/adovbs.inc"--><% Dim objConn Dim objRst Dim strSQL Dim strConnection Dim str Dim str1 Dim cnt Dim cnt1 Dim rndMax Dim RndNumber strConnection="driver={Microsoft Access Driver (*.mdb)};dbq=" & server.mappath("/testdb.mdb") strSQL = "SELECT id FROM tblQuestions" set objConn = Server.CreateObject("ADODB.Connection") Set objRst = Server.CreateObject("ADODB.Recordset") objConn.Open strConnection set objRst.ActiveConnection = objConn objRst.LockType = adLockOptimistic objRst.CursorType = adOpenKeySet objRst.Open strSQL objRst.MoveLast cnt = objRst.RecordCount cnt1 = cnt rndMax = cnt If CInt(Request.Form("maxNumber")) < cnt Then cnt1 = CInt(Request.Form("maxNumber")) End If str = "," str1 = "," Do Until cnt1 = 0 Randomize RndNumber = Int(Rnd * rndMax) If (InStr(1, str1, "," & RndNumber & "," ) = 0) Then str1 = str1 & RndNumber & "," cnt1 = cnt1 - 1 objRst.MoveFirst objRst.Move RndNumber str = str & objRst("id") & "," End If Loop objRst.Close Set objRst = Nothing sql = "SELECT * FROM tblQuestions WHERE (((InStr(1,'" & str & "',(',' & [id] & ',')))<>0)) " Set objRst = Server.CreateObject("ADODB.Recordset") set objRst.ActiveConnection = objConn objRst.LockType = adLockOptimistic objRst.CursorType = adOpenKeySet objRst.Open sql%>...DISPLAY THE RECORDS RETURNED...<%objRst.CloseSet objRst = NothingobjConn.CloseSet objConn = Nothing%> |
I'd be interested in hearing from anyone that builds upon this and/or how they put it to use!
See Ya!
Larry Boggs