MySQL数据 - 同时计算电话号码

Question

我有一个带有电话的MySQL表.每行意味着一个电话.列是:

start_time
start_date
duration

我需要同时拨打最多的电话.这是因为电话交换尺寸.

我的解决方案是创建两个时间戳列timestamp_start和timestamp_end.然后我每天一秒钟地运行循环,并向MySQL询问类似于:

SELECT Count(*) FROM tbl WHERE start_date IN (thisday, secondday) AND "this_second_checking" BETWEEN timestamp_start AND timestamp_end;

这很慢.有更好的解决方案吗？谢谢!

编辑 - 我使用这个解决方案,它给了我正确的结果.使用了SQL层dibi - http://dibiphp.com/cs/quick-start.

$starts = dibi::query("SELECT ts_start, ts_end FROM " . $tblname . " GROUP BY ts_start");
if(count($starts) > 0):
  foreach ($starts as $row) {
    if(isset($result)) unset($result);
    $result = dibi::query('SELECT Count(*) FROM ' . $tblname . ' WHERE "'.$row->ts_start.'" BETWEEN ts_start AND ts_end');
    $num = $result->fetchSingle();
    if($total_max < $num):
      $total_max = $num;
    endif;    
  }  
endif;
echo "Total MAX: " . $total_max;

Answer 1

您应该为每一行(电话呼叫)查看当时其他电话是否处于活动状态,而不是逐秒运行它.之后,您按行的ID对所有结果进行分组,并检查哪个具有最大计数.所以基本上是这样的:

SELECT MAX(calls.count)
FROM (
    SELECT a.id, COUNT(*) AS count
    FROM tbl AS a
    INNER JOIN tbl AS b ON (
        (b.timestamp_start BETWEEN a.timestamp_start AND a.timestamp_end)
        OR
        (b.timestamp_end BETWEEN a.timestamp_start AND a.timestamp_end)
    )
    GROUP BY a.id
) AS calls

在timestamp列上创建索引也会有所帮助.