Question

我需要连接两个表：Cardealers和Applications。

我想看看哪些经销商已收到哪些应用程序。

每个应用程序都转发给三个cardealers，因此我的表结构包含以下3列：receiver_1，receiver_2，receiver_3。

接收者列中的ID与cardealer_id相同。

我的代码仅适用于一列和一列：

$res1 = $wpdb->get_results( " SELECT leads.*, cardealers.*
    FROM leads
    LEFT JOIN cardealers ON leads.receiver_1 = cardealers.cardealer_id
    WHERE leads.receiver_1 = cardealers.cardealer_id
    AND cardealers.cardealer_id = '". $cardealer_id ."'" );

$res2 = $wpdb->get_results( " SELECT leads.*, cardealers.*
    FROM leads
    LEFT JOIN cardealers ON leads.receiver_2 = cardealers.cardealer_id
    WHERE leads.receiver_2 = cardealers.cardealer_id
    AND cardealers.cardealer_id = '". $cardealer_id ."'" ); 

$res3 = $wpdb->get_results( " SELECT leads.*, cardealers.*
    FROM leads
    LEFT JOIN cardealers ON leads.receiver_3 = cardealers.cardealer_id
    WHERE leads.receiver_3 = cardealers.cardealer_id
    AND cardealers.cardealer_id = '". $cardealer_id ."'" );

正如你所看到的，我做了3个单独的陈述，这些陈述都有效。但我想将这些结合成一个陈述。

我该怎么做？

Answer 1

只需继续添加表格并将其别名。

SELECT 
   leads.*, cardealers1.*, cardealers2.*, cardealers3* 
FROM leads 
LEFT JOIN cardealers as cardealers1
   ON leads.receiver_1 = cardealers1.cardealer_id 
LEFT JOIN cardealers as cardealers2
   ON leads.receiver_2 = cardealers2.cardealer_id
LEFT JOIN cardealers as cardealers3
   ON leads.receiver_3 = cardealers3.cardealer_id
WHERE 
   leads.receiver_1 = cardealers1.cardealer_id 
   AND leads.receiver_2 = cardealers2.cardealer_id 
   AND leads.receiver_3 = cardealers3.cardealer_id 
   AND cardealers.cardealer_id = '". $cardealer_id ."'

编辑：如果你为每个cardealers的列提供别名，那就最好了

左连接两个表，多列

1 个答案: