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我的问题是我目前正在编写的客户服务数据库。我对 sql 查询了解不多，而且我真的很难正确查询。

我有两张桌子：

**Customers:**
idcustomer
company_name
tel_number
address
postcode

**customer_machines**
id_customer_machine
id_customer
date_last_service
date_service_due

我想选择显示在给定日期集之间哪些机器到期提供服务的结果（例如机器在第 9 个月到期）。

SELECT customer_machines.* from customer_machines WHERE (customer_machines.date_next_service BETWEEN '2013-09-01' AND '2013-10-01') ORDER BY date_next_service ASC;

这很好，但是有些客户拥有不止一台机器，例如

+---------------------+-------------+-------------------+-------------------+
| id_customer_machine | id_customer | date_last_service | date_next_service |
+---------------------+-------------+-------------------+-------------------+
|                   1 |           1 | 2012-09-02        | 2013-09-02        |
|                   2 |           2 | 2012-09-14        | 2013-09-14        |
|                   3 |           3 | 2012-09-30        | 2013-09-30        |
|                   5 |           3 | 2012-09-30        | 2013-09-30        |
+---------------------+-------------+-------------------+-------------------+

我需要将客户拥有的机器分组，加入客户的详细信息并输出到浏览器中的表格，例如：

Customer 1     address of customer 1     tel of customer 1     postcode of customer 1
machine-id-1                                 date-last-service      date-next-service
------------------------------------------------------------------------------------
customer 2     address of customer 2     tel of customer 2     postcode of customer 2
machine-id-2                                 date-last-service     date-next-service
-------------------------------------------------------------------------------------
customer 3     address of customer 3     tel of customer 3     postcode of customer 3
machine-id-3                                date-last-service     date-next-service
machine-id-5                                date-last-service     date-next-service

我可以像这样通过单个查询将结果排列在一起吗？到目前为止，我只尝试过在 php 中嵌套查询，但没有成功。

如果你能指出我正确的方向那就太好了

谢谢

4

3 回答 3

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SQL 没有构建嵌套结果的功能，只有普通表。在一些简单的情况下，您可以使用GROUP_CONCAT来连接值。例如：

SELECT 
  id_customer, 
  GROUP_CONCAT(id_customer_machine SEPARATOR ', ') as id_customer_machines
FROM customer_machines;

会输出你：

+-------------+----------------------+
| id_customer | id_customer_machines |
+------------------------------------+
|           1 |                    1 |
|           2 |                    2 |
|           3 |                 3, 5 | 
+-------------+----------------------+

但是由于您需要对多个列进行分组，因此这对您没有帮助。在您的情况下，您有两种选择：

  1. 获取所有客户 ID，然后对其进行迭代，为每个 id_customer 获取客户机器。更简单，但效率不高（numCustomers + 1 个查询）。
  2. 从数据库中获取纯数据并通过 PHP 从中创建结构化数组。高效，但更多的编码。
于 2013-08-02T10:43:00.793 回答
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一种选择是从两个表中选择相关数据，例如：

SELECT c.*, cm.id_customer_machine, cm.date_last_service, cm.date_service_due from Customers c, customer_machines cm WHERE c.idcustomer = cm.customer_id AND (customer_machines.date_next_service BETWEEN '2013-09-01' AND '2013-10-01') ORDER BY date_next_service ASC;

但是，这可能并不理想，因为您最终也会为找到的每台机器获得重复的客户数据。

作为替代方案，您可以遍历每个客户并根据用户 ID 从第二个表中选择所有结果并将其构建到数组或对象中，例如：

$customerArr = array();

$con=mysqli_connect("localhost","user","pass","schema");

$customerResult = mysqli_query($con,"SELECT * FROM Customers");

while($customerRow = mysqli_fetch_array($customerResult)){

$customerArr[$customerRow['idcustomer']];

$macineResult = mysqli_query($con,"SELECT * FROM customer_machines WHERE customer_id = 'customerRow['idcustomer']'");

while($machineRow = mysqli_fetch_array($machineResult)){

$customerArr[$customerRow['idcustomer']][$machineRow['id_customer_machine']]['date_last_service'] = $machineRow['date_last_service'];

$customerArr[$customerRow['idcustomer']][$machineRow['id_customer_machine']]['date_next_service'] = $machineRow['date_next_service'];

}

}

希望这可以帮助。

于 2013-08-02T11:15:58.137 回答
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您可以使用单个查询来执行此操作，但是 PHP 代码中的循环会比使用单独的查询更复杂一些

SELECT * from customer_machines
INNER JOIN customers USING(customer_id)
WHERE (customer_machines.date_next_service BETWEEN '2013-09-01' AND '2013-10-01')
ORDER BY date_next_service ASC;

这应该给你类似的东西：

customer_id | machine_id | company_name | etc | other column | more data | ...
    1       |     1      | xxxx
    2       |     2      | xxxx
    3       |     3      | xxxx
    3       |     5      | xxxx

你的循环：

while($row = mysql_fetch_array($query)) {
    $data[ $row[customer_id][] = $row;
}

这将为您提供类似于以下内容的数组：

array(
    [1] => array(
         [0] => array(
              [company_name] => name,
              the remaining customer and machine data
         )
    ),
    [2] => array(
         [0] => array(
              [company_name] => name,
              the remaining customer and machine data
         )
    ),
    [3] => array(
         [0] => array(
              [company_name] => name,
              the remaining customer and machine data
         ),
         [1] => array(
              [company_name] => name,
              the remaining customer and machine data
         )
    )

只需遍历该数组即可打印数据；您将需要 2 个循环来执行此操作。

另一种解决方案是首先选择所有客户，遍历它并为每个客户选择要显示的机器信息。这样做你会得到很多查询。

于 2013-08-02T12:30:06.997 回答