Question

这是一个类似于我使用的简化代码。在这一个中，我从ID中提取姓名。

$counter = 0;
$select = "SELECT nID,nName WHERE nID = $counter";
$result = sqlsrv_query($connection, $select);

$maxusers = 10;

while($counter<$maxusers) {
  while($row = sqlsrv_fetch_array($result)) {
      echo $row['nName'];
  }
$counter++
}

我得到的是同一个名字，select语句中的计数器保持为0.

我必须将$ select语句的定义和$ result放在循环中，每次进入while循环时它都会重新定义所有内容，如下面的代码所示。这对我来说似乎不切实际和最佳。对于像这样的情况，最好的解决办法是什么？我并不熟悉PHP中的变量范围，在sql函数方面我还没有找到任何关于这个问题的好文档。

$counter = 0;
$maxusers = 10;

while($counter<$maxusers) {
$select = "SELECT nID,nName WHERE nID = $counter";
$result = sqlsrv_query($connection, $select);
  while($row = sqlsrv_fetch_array($result)) {
      echo $row['nName'];
  }
$counter++
}

这是我实际编写的代码。

$selectFirst = "SELECT TOP 1 nDateTime,nUserID FROM TB_EVENT_LOG WHERE nUserID = $usercounter AND nDateTime BETWEEN $today AND $tomorrow";
$selectLast = "SELECT TOP 1 nDateTime,nUserID FROM TB_EVENT_LOG WHERE nUserID = $usercounter DateTime BETWEEN $today AND $tomorrow DESC";

$resultFirst = sqlsrv_query($bscon, $selectFirst);      
$resultLast = sqlsrv_query($bscon, $selectLast);


$selectnumberofUsers = "SELECT TOP 1 nUserIdn FROM TB_USER ORDER by nUserIdn DESC";
$usersmaxq = sqlsrv_query($bscon, $selectnumberofUsers);
$usersmax = sqlsrv_fetch_object($usersmaxq)->nUserIdn;


while($usercounter<$usersmax){
    $usercounter = $usercounter + 1;

    while($rowfirst = sqlsrv_fetch_array($resultFirst)) {
        $intime = $rowfirst['nDateTime'];
    }
    echo $intime." ".$usercounter."<br />";
}

Answer 1

您的问题与变量范围无关。 $ select变量设置为字符串，其当前值为$ counter。您的第二个示例有效，因为每次都会重置此值。然而，在你的第二个例子中，你正在创建一个获得1行的sql语句（假设nID是唯一的），然后循环遍历你的结果检索那一行。您正在进行10次SQL调用，但如果修改查询，则只需要一次：

$minusers = 0;
$maxusers = 10;

$select = "SELECT nID,nName WHERE nID >= $minusers AND nID < $maxusers ORDER BY nID";

$result = sqlsrv_query($connection, $select);
while($row = sqlsrv_fetch_array($result)) {
    echo $row['nName'];
}

对于您的实际代码，您应该能够使用GROUP BY为每个nUserId获取一条记录。试试这个：

$selectFirst = "SELECT nDateTime,nUserID FROM TB_EVENT_LOG WHERE nUserID >= $usersmin AND nUserID <= $usersmax AND nDateTime BETWEEN $today AND $tomorrow GROUP BY nUserID";

预定义计数器未在select语句中更新

1 个答案: