Question

令人困惑，但是，情况如下：

我们得到的序列号对应于程序以1分钟为间隔的位置。

Sequence#  |  Timestamp
   1       |   2012-04-11 12:00:00
   2       |   2012-04-11 12:01:00
   2       |   2012-04-11 12:02:00
   2       |   2012-04-11 12:03:00
   3       |   2012-04-11 12:04:00
   5       |   2012-04-11 12:05:00
   5       |   2012-04-11 12:06:00
   6       |   2012-04-11 12:07:00
   1       |   2012-04-11 12:08:00
   2       |   2012-04-11 12:09:00
   2       |   2012-04-11 12:10:00
   2       |   2012-04-11 12:11:00
   3       |   2012-04-11 12:12:00

序列的持续时间可能会发生变化，但间隔始终相同（精确地每1分钟）。

如您所见，序列重复。 如何找到Seqence n的最新，首发？

所以，如果我想搜索序列2，我想返回2 | 2012-04-11 12:09:00，因为它是序列2的最新开始出现。

Answer 1

尝试：

SELECT t1.* FROM `table_name` t1
LEFT JOIN `table_name` t2 
on t1.`Sequence` = t2.`Sequence` and 
   t1.`Timestamp` = t2.`Timestamp` + interval 1 minute
WHERE t1.`Sequence`=2 and t2.`Sequence` is null
ORDER BY t1.`Timestamp` DESC LIMIT 1

SQLFiddle here。

Answer 2

我认为这就是你想要的......

SELECT * FROM `table_name` WHERE `Sequence`=2 ORDER BY `Timestamp` DESC LIMIT 1

Answer 3

这是你想要的吗？

$desired_sequence=2;

$query="SELECT * FROM `table_name` ORDER BY `Timestamp` DESC";
$result = mysql_query($query);
if (mysql_errno()) { die( "ERROR ".mysql_errno($link) . ": " . mysql_error($link) ); }

$found_desired=0;
while($row = mysql_fetch_array($result))
{
    if($row['Sequence']==$desired_sequence)
    {
        $found_desired=1;
        $timestamp=$row['Timestamp'];
    }

    if( ($found_desired==1) && ($row['Sequence']!=$desired_sequence) )
    {
        return; // End the while loop because $timestamp will have your desired output.
    }
}

Answer 4

我不确定你在这之后究竟是什么。我写了一些代码，如果数据在文本文件中，它将起作用。如果数据在数据库中，则会更容易。但是，我假设你的例子中有一个|分离它不在数据库中的数据。

function findLastOccurenceOfSequence ($sequenceNumber)
{
    if (@!is_int ($sequenceNumber))
        throw new Exception ("Expected param1 to be an integer");
    $data = file_get_contents ("testFile.txt");
    $dataArray = explode ("\n", $data);
    $dataArray = array_reverse ($dataArray);
    $returnLine = "";
    $sequenceStarted = false;
    foreach ($dataArray as $key => &$dataLine)
    {
        $pieces = explode ("|", $dataLine);
        if (count ($pieces) != 2)
            continue;
        list ($thisSequenceNum, $timeStamp) = $pieces;
        $thisSequenceNum = intval (trim ($thisSequenceNum));
        if ($thisSequenceNum == $sequenceNumber)
        {
            $sequenceStarted = true;
            $returnLine = $dataLine;
        }
        else if ($sequenceStarted)
        {
            break;
        }
    }

    if ($key == count ($dataArray))
    {
        throw new Exception ("Sequence not found!");
    }

    return $returnLine;
}

echo "OCCURRENCE: " . findLastOccurenceOfSequence (2);

选择最后一个分组中项目的第一个外观

4 个答案: