正确显示 mySQL 一对多查询的结果

Question

我有两张桌子：

      TRIPS
-----------------
tripID | clientID

和

              LEGS
--------------------------------
legID | depart | arrive | tripID

TRIPS 与 LEGS 具有一对多的关系，因为每个 tripID 有多个 legID。我需要以以下格式显示它们：

Trip tripID1:
    Leg legID1: depart1 - arrive1
    Leg legID2: depart2 - arrive2

Trip tripID2:
    Leg legID3: depart3 - arrive3
    Leg legID4: depart4 - arrive4

etc...

我已经能够通过WHILE() 循环遍历legID，但是在TRIPS 循环中嵌入LEGS 循环时遇到了问题。我的查询是：

<?php
$legsQuery = "SELECT  trips.tripID, legs.depart, legs.arrive FROM legs, trips WHERE `trips`.tripID = `legs`.tripID";
$legsQueryResult = mysql_query($legsQuery) or die("QUERY LEG ERROR: " . mysql_error());
while($row = mysql_fetch_assoc($legsQueryResult)) {
    print_r($row);
}
?>

Answer 1

1. 添加 order by 子句以按行程 ID 排序
2. 创建$lastTripID 变量以检查您何时从“新行程”中获得“腿”
3. [推荐]使用join从多个表中选择数据

代码：

<?php
    $legsQuery = "
        select  
            trips.tripID, 
            legs.depart, 
            legs.arrive 
        from 
            legs
            inner join trips on trips.tripID = legs.tripID
        order by
            trips.tripID
    ";
    $legsQueryResult = mysql_query($legsQuery) or die("QUERY LEG ERROR: " . mysql_error());
    $lastTripID = null;
    while ($row = mysql_fetch_assoc($legsQueryResult)) {
        if ( $row['tripID'] !== $lastTripID ) {
            echo $row['tripID'], "\n";
            $lastTripID = $row['tripID'];
        }
        print_r($row);
    }