< %
sessionID = session.SessionID
timeout = 30
' 设置session的过期时间
Conn_String = "DRIVER={Microsoft Access Driver (*.mdb)};DBQ=" & Server.MapPath("count.mdb")
'建立数据库连接项
Set ConnCount =Server.CreateObject("ADODB.Connection")
ConnCount.Open Conn_String
' dateadd函数的运用,指定n分钟为计量单位,计算now()+(-timeout)是时间,也就是过期时间
aaa = dateadd("n", -timeout, now())
connCount.Execute ("delete * from count where postdate < #" & aaa & "#")
'连接变量也可以用execute方法,对数据库进行操作,注意时间变量要用#隔开
' 以下语句是检查客户sessionID是否在数据库中,如果不是就加入,客户如果是第一次访问那么数据库中没有值.也是用连接变量的execute方法,注意insert into count (sess,postdate) values('"&sessionID&"','"&now()&"')"运用
sql0 = "select sess from count where sess='" & sessionID & "'"
set rscheck = connCount.Execute (sql0)
if rscheck.eof then
sql = "insert into count (sess,postdate) values('" & sessionID & "', '" & now() & "')"
connCount.Execute (sql)
end if
rscheck.close
set rscheck = nothing
'计算数据库中的值,count(sess)产生新的值,最终用rs(0)读出
sql2 = "select count(sess) from count"
set rs = connCount.Execute (sql2)
count = rs(0)
rs.close
set rs = nothing
'再对数据进行全盘检查看看是否有超期的数据,有则数据count减一
sql3 = "select * from count"
set rspredel = connCount.Execute (sql3)
do until rspredel.eof
xxx=DateDiff("n", rspredel("postdate"), Now())
if xxx > timeout then
count = count-1
end if
rspredel.movenext
loop
rspredel.close
set rspredel = nothing
connCount.Close
set connCount = nothing
if count = 0 then
count = 1
end if
% >
document.write('当前<%=count%>人在线');
'最终得出结果
'要计数的页面中还要,插入<script language="javascript" src="XXXX/online.asp"></script>
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