MySQL : merge data from 3 tables in one result with one query statement

Question

要在一个查询中合并来自 invoice 和 clients 表的发票和相应的客户地址数据，我使用以下语句:

SELECT * 
FROM invoice, clients 
WHERE invoice.client_id = clients.ID

它工作完美。但是现在我有第三个表进入游戏，其中存储了 invoice_items。每张发票都有一项或多项将向客户收费的项目。每个 invoice_item UPDATE 存储相应的、先前生成的 invoice.ID。但是如何在一个查询中合并 3 个表呢？我这样试过:

SELECT * 
FROM invoice, invoice_item, clients 
WHERE inv_num =:num 
AND invoice.client_id = clients.ID  
AND invoice_item.inv_id = invoice.ID

但是到目前为止我还没有成功。我做错了什么？

感谢任何帮助。

编辑:整个语句如下所示:

$query = $this->db_con->prepare('SELECT * FROM invoice, invoice_item, clients  WHERE inv_num =:num AND invoice.client_id = clients.ID AND invoice_item.inv_id = invoice.ID');
$query->bindValue(':num',$val, PDO::PARAM_STR);
$success = $query->execute();

$val 是之前从表格中选择的发票编号。

更新:

根据 Stivan 的回答，我得到了以下结果模式。 假设有 1 张发票和 2 个 invoice_item:

    Array {
     [0] => Array {
            // col from table `invoice`
            [col 1]
            [col 2]
            [col n] 
            // col from table `invoice_item`
            [col 1]
            [col 2]
            [col n] 
            // col from table `clients`
            [col 1]
            [col 2]
            [col n] 
      }
     [1] => Array {
            // col from table `invoice`
            [col 1]
            [col 2]
            [col n] 
            // col from table `invoice_item`
            [col 1]
            [col 2]
            [col n] 
            // col from table `clients`
            [col 1]
            [col 2]
            [col n] 
      }
   }

换句话说，在每个数组中，我从参与表中获取所有列，其中表invoice和clients中有冗余内容。

如何将列从 clients 分隔为 1 col？

或者甚至更好地保存资源并仅接收 1 个带有 * 来自发票和来自 invoice_items 的附加项目的数组，所以它可能看起来像这样:

Array {
 [0] => Array {
        // col from table `invoice`
        [col 1]
        [col 2]
        [col n] 
        // col from table `clients`
        [col 1]
   }
         Array {
            [0] => Array {
                   // col from table `invoice_items`
                   [col 1]
                   [col 2]
                   [col n] 
                  }
            [1] => Array {
                   // col from table `invoice_items`
                   [col 1]
                   [col 2]
                   [col n] 
                  }
          }
 }

Answer 1

select
     *
from invoice
     left join invoice_item on invoice_item.inv_id = invoice.ID
     left join clients on clients.ID = invoice.client_id
where
     invoice.inv_num = :num;  //Or the table where inv_number comes from

 corrected invoice.inv_number to invoice.inv_num