如何使用 PHP 数组模拟 SQL LEFT JOIN 操作？

Question

我有一个连接到多个服务器的应用程序。其中一台服务器的 ID 是位于另一台服务器上的表的外键。这里的问题是 MySQL 不支持链接服务器，因此我无法运行将 LEFT 连接位于不同服务器上的 2 个表的左查询。

所以我必须使用 PHP 从 2 个不同的服务器中提取 2 个单独的查询，然后他们使用 PHP 来加入它们。

请注意，下面列出的数组键需要是动态的。我不能使用固定名称，因为不同的查询会有不同的列名。下面的示例使用 phone_call_id 作为它们用于连接两个数组的键，并结合了列名。如果 $right_array 有更多列，则需要将这些列添加到最终数组中。

所以我有 2 个数组

$left_array = 
Array
(
    [0] => Array
        (
            [id] => 1
            [start_on] => 2014-09-14 19:50:00
            [end_on] => 2014-09-14 19:51:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 122
        )

    [1] => Array
        (
            [id] => 2
            [start_on] => 2014-09-15 05:53:00
            [end_on] => 2014-09-15 06:53:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 123
        )

    [2] => Array
        (
            [id] => 3
            [start_on] => 2014-09-15 05:53:00
            [end_on] => 2014-09-15 06:53:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 
        )
)

正确的数组将如下所示

$right_array = 
Array
(
    [0] => Array
        (
            [account_id] => 1
            [phone_call_id] => 122
        )

    [1] => Array
        (
            [account_id] => 2
            [phone_call_id] => 123
        )
)

结果需要像这个数组

$joined_array = 
Array
(
    [0] => Array
        (
            [id] => 1
            [start_on] => 2014-09-14 19:50:00
            [end_on] => 2014-09-14 19:51:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 122
            [account_id] => 1
        )

    [1] => Array
        (
            [id] => 2
            [start_on] => 2014-09-15 05:53:00
            [end_on] => 2014-09-15 06:53:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 123
            [account_id] => 2
        )

    [2] => Array
        (
            [id] => 3
            [start_on] => 2014-09-15 05:53:00
            [end_on] => 2014-09-15 06:53:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 
            [account_id] =>

        )
)

Answer 1

该函数模拟左连接操作

   //function to simulate the left join
    function left_join_array($left, $right, $left_join_on, $right_join_on = NULL){
        $final= array();

        if(empty($right_join_on))
            $right_join_on = $left_join_on;

        foreach($left AS $k => $v){
            $final[$k] = $v;
            foreach($right AS $kk => $vv){
                if($v[$left_join_on] == $vv[$right_join_on]){
                    foreach($vv AS $key => $val)
                        $final[$k][$key] = $val; 
                } else {
                    foreach($vv AS $key => $val)
                        $final[$k][$key] = NULL;            
                }
            }
        }
       return $final;
    }

//该函数可以像这样使用，假设左侧数组中的列名与右侧数组中的列名相同

$final_array = left_join_array($left, $right, 'phone_call_id');

//该函数可以像这样使用，假设左数组中的列名“不同但具有相同的对应值”

$final_array = left_join_array($left, $right, 'phone_call_id', 'p_c_id');