PL SQL xmlelement：如何从同一张表的互斥条件中获取xml中的数据

Posted 2023-03-28

【中文标题】PL SQL xmlelement：如何从同一张表的互斥条件中获取xml中的数据

【英文标题】：PL SQL xmlelement: How to get data in xml from mutually exclusive condition on same tables

【发布时间】：2016-11-06 05:21:32

【问题描述】：

我正在使用 XML 从数据库中获取一些数据。这是我的桌子：

设置表：

class   code    name
'm1'    1       Food1
'm1'    2       Food2
'p1'    1       PayInCash
'p2'    2       PayOnline

Customer Table:
customer_id  food_name  payment_method
CUS123          1         1 
CUS123          2         2 

如您所见，我使用了一些内部代码来映射其详细信息

我想编写将给出以下输出的查询：

Query Output:
customer_id  food_name  payment_method
CUS123          Food1      PayInCash 
CUS123          Food2      PayOnline

我想检索 XML 格式的数据，这就是我使用 xmlelement 的原因。

SELECT xmlelement("customer_records",
                   XMLAGG(
                        xmlelement("record",
                            xmlelement("cus_id", customer_id),
                            xmlelement("food", food_name),
                            xmlelement("payment", payment_method)
                        )
                    )
             )

            FROM Customer 
            WHERE customer_id = 'CUS123';

您可以看到，由于条件，我无法加入。 请帮忙。

【参考方案1】：

尝试依赖子查询，方式如下：

SELECT customer_id,
       ( SELECT name FROM Settings s
         WHERE class LIKE 'm%' AND s.code = c.food_name ) AS food_name,
       ( SELECT name FROM Settings s
         WHERE class LIKE 'p%' AND s.code = c.payment_method ) AS payment_method 
FROM customer c;

---

使用 XMLAGG 的示例：

SELECT xmlelement("customer_records",
                   XMLAGG(
                        xmlelement("record",
                            xmlelement("cus_id", customer_id),
                            xmlelement("food", food_name),
                            xmlelement("payment", payment_method)
                        )
                    )
             )
FROM (
      SELECT customer_id,
             ( SELECT name FROM Settings s
               WHERE class LIKE 'm%' AND s.code = c.food_name ) AS food_name,
             ( SELECT name FROM Settings s
               WHERE class LIKE 'p%' AND s.code = c.payment_method ) AS payment_method 
      FROM customer c
);

结果：

<customer_records>
    <record>
        <cus_id>CUS123</cus_id>
        <food>Food1</food>
        <payment>PayInCash</payment>
    </record>
    <record>
        <cus_id>CUS123</cus_id>
        <food>Food2</food>
        <payment>PayOnline</payment>
    </record>
</customer_records>