Question

我想连接数据库并每隔1秒从一个字段中检索数据。这会加载第一条记录，但不会请求/显示任何新记录。有什么想法吗？

function test() {
  var adOpenForwardOnly = 0,
    adLockReadOnly = 1;
  var conn = new ActiveXObject("ADODB.Connection");
  conn.open("Provider=Microsoft.Jet.OLEDB.4.0;Data          Source=C:\\path\\Data.mdb;Persist Security Info=False");
  if (conn) {
    var rs = new ActiveXObject("ADODB.Recordset");
    rs.Open("SELECT Table1.* FROM Table1 where Time1 = time()", conn, adOpenForwardOnly, adLockReadOnly);
    value1 = rs.fields("Value1").value;
    document.write(value1);
  }
  rs.Close();
  conn.Close();
}
setTimeout(test(), 1000);

Answer 1

如果你这样尝试会怎么样？

function test() {
  var adOpenForwardOnly = 0,
      adLockReadOnly = 1;

  try {
    var conn = new ActiveXObject("ADODB.Connection");
    conn.open("Provider=Microsoft.Jet.OLEDB.4.0;DataSource=C:\\path\\Data.mdb;Persist Security Info=False");
    if (conn.State > 0) {
      var rs = new ActiveXObject("ADODB.Recordset");
      rs.Open("SELECT Table1.* FROM Table1 where Time1 = time()", conn, adOpenForwardOnly, adLockReadOnly);
      value1 = rs.fields("Value1").value;
      document.write(value1);
    } else {
      throw new Error('conn not open...');
    }
    rs.Close();
    conn.Close();
  } catch (someError) {
    alert(someError.message);
  }
}

var i = 0;
while (i === 0) {
  setTimeout(test, 1000);
}

Answer 2

您的代码存在两个问题：

您使用setTimeout代替setInterval，因此它只会执行一次。
您使用括号()将函数作为参数发送，但您应该只命名该函数，例如：setInterval(test, 1000);

另一个选项

我建议您使用递归setTimeout（导致数据库延迟）。 E.g：

function test() {
  var adOpenForwardOnly = 0,
    adLockReadOnly = 1;
  var conn = new ActiveXObject("ADODB.Connection");
  conn.open("Provider=Microsoft.Jet.OLEDB.4.0;Data          Source=C:\\path\\Data.mdb;Persist Security Info=False");
  if (conn) {
    var rs = new ActiveXObject("ADODB.Recordset");
    rs.Open("SELECT Table1.* FROM Table1 where Time1 = time()", conn, adOpenForwardOnly, adLockReadOnly);
    value1 = rs.fields("Value1").value;
    document.write(value1);
  }
  rs.Close();
  conn.Close();

  setTimeout(test, 1000);
}

test();

通过Javascript请求MS Access数据

2 个答案: