XML直接通過查詢ORACLE db

Question

我在查詢Oracle數據庫，使用XMLELEMENT和XMLFOREST在每行中創建XML。 對於單表它工作正常。但我的要求是現在從3個不同的表中獲取數據。

描述：

表主要，SecondTable，ThirdTable。其中Main和SecondTable具有唯一的TxnID，而在ThirdTable中它重複。

例子：

Main Table      SecondTable      ThirdTable 

TxnId A B C    D TxnId E F     G H I TxnId 

1001 3 4 6    5 1001 6 2     2 5 5 1001 
1002 5 6 2    4 1002 5 6     6 8 9 1001 
1003 5 4 2    6 1003 5 6     8 9 8 1001 

我想reperesent在XML這些數據，到目前爲止，我能夠用得到的XML的形式第一行，

Select XMLELELEMENT(("Event", XMLFOREST(m.A as 'A', 
             m.B as 'B', 
             m.C as 'C') || 
           XMLELEMENT("SecondTable", 
             XMLFOREST(s.E as 'E', 
                s.F as 'F')) || 
           XMLELEMENT("ThirdTable", 
             XMLFOREST(t.G as 'G', 
                t.H as 'H', 
                t.I as 'I'))) 
    from Main m 
    JOIN SecondTable s 
    ON m.TxnId=s.TxnId 
    JOIN ThirdTable t 
    ON s.TxnId=t.TxnId 

該查詢會給我輸出like--

<Event> 
    <Main> 
     <A>3</A> 
     <B>4</B> 
     <C>6</C> 
    </Main> 
    <SecondTable> 
     <E>6</E> 
     <F>2</F> 
    </SecondTable> 
     <ThirdTable> 
      <G>2</G> 
      <H>5</H> 
      <I>5</I> 
     </ThirdTable> 
</Event> 

問題：ThirdTable的我想重複TxnIds形成3阻止在一個單一的XML。我希望我很清楚。 請幫幫我。 在此先感謝。

Answer 1

您可以使用xmlagg函數以及group by子句來實現此目的。我還包括一個outter加入到ThirdTable。請在下面看到我的解決方案，希望這有助於：

情況下設置：

  create table main 
      (txnid number(4),a VARCHAR2(1), b VARCHAR2(1), c VARCHAR2(1)); 

      insert into main values (1001, 3 ,4 ,6); 
      insert into main values (1002, 5 ,6 ,2); 
      insert into main values (1003, 5 ,4 ,2); 

      create table secondtable 
      (d VARCHAR2(1),txnid number(4), e VARCHAR2(1), f VARCHAR2(1)); 

      insert into secondtable values (5, 1001 ,6 ,2); 
      insert into secondtable values (4, 1002 ,5 ,6); 
      insert into secondtable values (6, 1003 ,5 ,6); 

      create table thirdtable 
      (g VARCHAR2(1), h VARCHAR2(1), i VARCHAR2(1), txnid number(4)); 


      insert into thirdtable values (2, 5 ,5 ,1001); 
      insert into thirdtable values (6, 8 ,9 ,1001); 
      insert into thirdtable values (8, 9 ,8 ,1001); 

      commit; 

查詢：

  select XMLELEMENT("Event", xmlelement("Main", 
              XMLFOREST(m.A as "A", 
                m.B as "B", 
                m.C as "C")), 
              XMLELEMENT("SecondTable", 
                 XMLFOREST(s.E as "E", 
                   s.F as "F")) , 
              xmlagg(XMLELEMENT("ThirdTable", 
                 XMLFOREST(t.G as "G", 
                   t.H as "H", 
                   t.I as "I")))) xml_payload 
      from main m, secondtable s, thirdtable t 
      where m.TxnId=s.TxnId 
      and s.TxnId=t.TxnId(+) 
      group by m.txnid, s.txnid, m.a, m.b, m.c, s.e, s.f; 

替代，使用子選擇，並通過與outter刪除組加入：

  select XMLELEMENT("Event", xmlelement("Main", 
               XMLFOREST(m.A as "A", 
                  m.B as "B", 
                  m.C as "C")), 
                XMLELEMENT("SecondTable", 
                  XMLFOREST(s.E as "E", 
                     s.F as "F")),               
                (select xmlagg(XMLELEMENT("ThirdTable", 
                  XMLFOREST(t.G as "G", 
                     t.H as "H", 
                     t.I as "I"))) 
                from thirdtable t 
                where s.TxnId=t.TxnId 
                )) xml_payload 
        from main m, secondtable s 
        where m.TxnId=s.TxnId; 

將第三張表格中的所有元素都重複一次只是將xmlagg向下移動一級：

  select XMLELEMENT("Event", xmlelement("Main", 
               XMLFOREST(m.A as "A", 
                  m.B as "B", 
                  m.C as "C")), 
                XMLELEMENT("SecondTable", 
                  XMLFOREST(s.E as "E", 
                     s.F as "F")),               
                (select XMLELEMENT("ThirdTable",xmlagg(
                  XMLFOREST(t.G as "G", 
                     t.H as "H", 
                     t.I as "I"))) 
                from thirdtable t 
                where s.TxnId=t.TxnId 
                )) xml_payload 
        from main m, secondtable s 
        where m.TxnId=s.TxnId;