如何使用 PL SQL 输出这种 XML 格式

Question

我想写一个pl sql函数，以以下xml格式返回oracle表数据：

<loans>
<loan>
<id>1</id>
<name>Bank Loan</name>
<description>Bank Loan-1</description>
<amount>25000</amount>
<sanction_date>2016-01-27</sanction_date>
<rate>4.5</rate>
</loan>

<loan>
<id>2</id>
<name>Bank 2</name>
<description>Bank Loan-2</description>
<amount>452500</amount>
<sanction_date>2016-01-27</sanction_date>
<rate>7.67</rate>
</loan>

<loan>
<id>3</id>
<name>New Loan</name>
<description>NY Bank Loan</description>
<amount>1250000</amount>
<sanction_date>2016-01-27
</sanction_date>
<rate>12.25</rate>
</loan>
</loans>

但不是上面的格式，它给了我下面的格式，有许多 loans 标签而不是一个作为父标签：

<loans>
<loan>
<id>1</id>
<name>Bank Loan</name>
<description>Bank Loan-1</description>
<amount>25000</amount>
<sanction_date>2016-01-27</sanction_date>
<rate>4.5</rate>
</loan>
</loans>

<loans>
<loan>
<id>2</id>
<name>Bank 2</name>
<description>Bank Loan-2</description>
<amount>452500</amount>
<sanction_date>2016-01-27</sanction_date>
<rate>7.67</rate>
</loan>
</loans>

<loans>
<loan>
<id>3</id>
<name>New Loan</name>
<description>NY Bank Loan</description>
<amount>1250000</amount>
<sanction_date>2016-01-27
</sanction_date>
<rate>12.25</rate>
</loan>
</loans>

作为初学者，我认为我以错误的方式排列它们。这是我的 PL SQL 代码：

SELECT xmlagg
             (
              xmlelement("loans",                                        
                    XMLAGG(
                        xmlelement("loan",
                           xmlelement("id", e.LNTYPE_ID), 
                           xmlelement("name", e.LNTYPE_NAME), 
                           xmlelement("description", e.LNTYPE_DESCRIPTION),
                           xmlelement("amount", e.LNTYPE_AMOUNT),
                           xmlelement("sanction_date", e.LNTYPE_SANCTION_DATE),
                           xmlelement("rate", e.LNTYPE_INTEREST_RATE)
                           )
                        )
                       )
              )
        as clob 
    FROM TBL_LOAN_TYPE e
    group by e.LNTYPE_ID;

Answer 1

你很亲密，你只需要摆脱外面的 xmlagg 和 group by：

SELECT xmlelement("loans",                                        
         XMLAGG(
           xmlelement("loan",
             xmlelement("id", e.LNTYPE_ID), 
             xmlelement("name", e.LNTYPE_NAME), 
             xmlelement("description", e.LNTYPE_DESCRIPTION),
             xmlelement("amount", e.LNTYPE_AMOUNT),
             xmlelement("sanction_date", e.LNTYPE_SANCTION_DATE),
             xmlelement("rate", e.LNTYPE_INTEREST_RATE)
          )
        )
      ) as clob 
FROM TBL_LOAN_TYPE e;

编辑：当您在 e.LNTYPE_ID 上使用 group by 时，您实际上会得到三个单独的行，因为 ID 都是唯一的。例如运行这段代码：

SELECT xmlelement("loans",                                        
         XMLAGG(
           xmlelement("loan",
             xmlelement("id", e.LNTYPE_ID), 
             xmlelement("name", e.LNTYPE_NAME), 
             xmlelement("description", e.LNTYPE_DESCRIPTION),
             xmlelement("amount", e.LNTYPE_AMOUNT),
             xmlelement("sanction_date", e.LNTYPE_SANCTION_DATE),
             xmlelement("rate", e.LNTYPE_INTEREST_RATE)
          )
        )
      ) as clob 
FROM TBL_LOAN_TYPE e
GROUP BY e.LNTYPE_ID;

将返回三个独立的 XML 片段，每个贷款一个。然后，外部 XMLAGG 将这些组合成一个 XML 文档，您可以在此处阅读有关 XMLAGG 的更多信息：https://docs.oracle.com/cd/B19306_01/server.102/b14200/functions215.htm