Php 列具有相同名称时如何保持连接打开

标题有点让人困惑，希望能从我的查询中清楚地看出我想做什么。我以为我理解联接，但显然不是，这是我的$查询：

     SELECT DATE(T0.timestamp),
            SUM(T0.total_responses), 
            SUM(T0.responses), 
            T0.metric_id, 
            T1.metric_id
       FROM `personal_aggregates` AS T0
  LEFT JOIN `qrs_metrics` AS T1 
         ON T0.metric_id = T1.qrs_metric_id
      WHERE T0.user_id = 1 AND 
            T0.duration = '1' AND 
            T0.category_id IN (1,2,3,4) AND 
            T0.timestamp >= 'period_duration'
   GROUP BY DATE(T0.timestamp)";

我正在尝试联接metric_id和qrs_metric_id列上的表。但是，我从上述查询中没有得到任何结果。当我在PHP中循环遍历结果并检查任何变量时，例如

$result['T0.metric\u id']

，我得到

未定义的索引：T0.metric\u id

如果有人能对此有所了解，我将不胜感激。

您的问题应该是

$query = "SELECT 
                DATE(T0.timestamp) AS T0timestamp, 
                SUM(T0.total_responses) AS total_responses, 
                SUM(T0.responses) AS responses,
                T0.metric_id, 
                T1.metric_id AS metric_id_2
        FROM `personal_aggregates` AS T0

就像

$result['metric_id'];
$result['metric_id_2'];
$result['T0timestamp'];
$result['total_responses'];

从关联数组访问中排除表别名，例如“T0.XXX”错误。您只能在SQL中执行此操作，请尝试以下操作：

$query = "SELECT DATE(T0.timestamp), SUM(T0.total_responses), SUM(T0.responses),
               T0.metric_id AS metric0, T1.metric_id AS metric1
        FROM `personal_aggregates` AS T0
        LEFT JOIN `qrs_metrics` AS T1 ON T0.metric_id = T1.qrs_metric_id
        WHERE T0.user_id = 1 AND T0.duration = '1'
        AND T0.category_id IN (1,2,3,4)
        AND T0.timestamp >= 'period_duration'
        GROUP BY DATE(T0.timestamp)";

现在，您可以使用以下方法来改变现状：

echo $row['metric0'];
echo $row['metric1'];

---

或者需要向选定列添加一些别名

SELECT DATE(T0.timestamp) as tstamp, SUM(T0.total_responses) as responses...

并按别名引用列：

$result['tstamp']

或者，您可以通过数字索引引用列：

$result[0]

---

请下次格式化您的SQL代码。没有人愿意读一行巨大的厄运。如果你直接在MySQL（工作台或命令行）中运行查询，你会得到结果吗？连接是正确的，是PHP在这里表现不好。我建议在查询中添加列别名：

选择T0.metric\u id作为T0\u metric\u id，T1.metric\u id作为T1\u metric\u id，…

，然后在PHP中将它们读为

$row['T0\u metric\u id']

和

$row['T1\u metric\u id']

@Trent是的，我已经通过phpmyadmin尝试过了表结构是什么？（似乎个人_聚合没有度量_Id列？（也许您需要按T0.metric_Id和T1.metric_Id进行分组）和别名T0&T1.metric_Id..太棒了，请注意。首先将此标记为答案。