165.Oracle数据库SQL开发之 XML和ORACLE——从关系数据生成XML
165.Oracle数据库SQL开发之 XML和ORACLE——从关系数据生成XML
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ORACLE数据库包含很多SQL函数，使用这些函数可以生成XML。
1. XMLELEMENT()
可以从关系数据生成XML元素。
store@PDB1> selectxmlelement("customer_id",customer_id) as xml_customers fromcustomers;
XML_CUSTOMERS
----------------------------------------------------------------------------------------------------
2. XMLATTRIBUTES()
可以指定由XMLELEMENT检索的XML元素的属性。
store@PDB1> selectxmlelement("customers",xmlattributes(customer_id as"id",first_name || ' ' ||last_name as "name",
to_char(dob,'MM/DD/YYYY') as "dob")) as xml_customers fromcustomers where customer_id in (1,2)
XML_CUSTOMERS
----------------------------------------------------------------------------------------------------
3. XMLFOREST()
可以生成XML元素的树形结构。可以将元素连接在一起，而不必使用连接操作符||多次调用XMLELEMENT().
store@PDB1> selectxmlelement("customer",xmlattributes(first_name||' '|| last_name as"name"),
xmlforest(phone as "phone",to_char(dob,'MM/DD/YYYY') as"dob")) as xml_customers from customers where customer_id in (1,2);
XML_CUSTOMERS
----------------------------------------------------------------------------------------------------
4. XMLAGG()
从XML元素集合生成XML元素的树形结构。
store@PDB1> selectxmlelement("product_list",xmlagg(xmlelement("product_type_and_avg",product_type_id||''||avg(price) )
order by product_type_idnulls last)) as xml_products from products group by product_type_id;
XML_PRODUCTS
----------------------------------------------------------------------------------------------------
oduct_type_and_avg>
5. XMLCOLATTVAL()
可以创建XML片段，然后扩展生成的XML。
store@PDB1> selectxmlelement("customer",xmlcolattval(customer_id as "id",dobas "dob",phone as "phone"))
asxml_customers from customers where customer_id in (1,2);
XML_CUSTOMERS
----------------------------------------------------------------------------------------------------
6. XMLCONCAT
可以将每行的一系列元素连接起来。
store@PDB1> selectxmlconcat(xmlelement("first name",first_name),xmlelement("lastname",last_name),
xmlelement("phone",phone))
asxml_customers from customers where customer_id in (1,2);
XML_CUSTOMERS
----------------------------------------------------------------------------------------------------
7. XMLPARSE
可以对表达式的求职结果进行解析并生成XML。
store@PDB1> select xmlparse( content'
asxml_customer from dual;
XML_CUSTOMER
----------------------------------------------------------------------------------------------------
8. XMLPI
可以生成XML处理指令。
store@PDB1> select xmlpi( name"order_status",'placed,pending,shipped') as xml_order_status_pi fromdual;
XML_ORDER_STATUS_PI
----------------------------------------------------------------------------------------------------
9. XMLCOMMENT
可以生成XML注释，注释是放在中的一个文本字符串。
store@PDB1> select xmlcomment('An example XMLComment') as xml_comment from dual;
XML_COMMENT
----------------------------------------------------------------------------------------------------
10. XMLSEQUENCE
可以生成XMLSequenceType对象。
store@PDB1> select value(list_of_values).getstringval() order_values fromtable(xmlsequence(extract(xmltype('PLACEDPENDINGSHPPED'),'/A/B')))list_of_values
ORDER_VALUES
----------------------------------------------------------------------------------------------------
PLACED
PENDING
SHPPED
11. XMLSERIALIZE
使用XMLSERIALZE可以将表达式的求值结果表示为字符串或LOB类型的XML数据。
必须在表达式前面使用下列关键字之一：
l CONTENT，意味着表达式必须解析为一个有效的XML值
l DOCUMENT，意味表达式必须解析为带有唯一根元素的XML文档
store@PDB1> select xmlserialize( contentxmltype('
XML_ORDER_STATUS
--------------------------------------------------------------------------------
12. 将XML数据写入文件
将顾客名写到一个XML文件。
system@PDB1> grant create any directory to store;
Grant succeeded.
store@PDB1> create directory temp_file_dir as'/home/oracle/temp_file';
Directory created.
执行xml_examples.sql脚本如下：
CREATE PROCEDURE write_xml_data_to_file(
p_directoryVARCHAR2,
p_file_nameVARCHAR2
) AS
v_fileUTL_FILE.FILE_TYPE;
v_amountINTEGER := 32767;
v_xml_dataXMLType;
v_char_bufferVARCHAR2(32767);
BEGIN
-- open thefile for writing of text (up to v_amount
-- charactersat a time)
v_file :=UTL_FILE.FOPEN(p_directory, p_file_name, 'w', v_amount);
-- write thestarting line to v_file
UTL_FILE.PUT_LINE(v_file, '');
-- retrievethe customers and store them in v_xml_data
SELECT
EXTRACT(
XMLELEMENT(
"customer_list",
XMLAGG(
XMLELEMENT("customer", first_name || ' ' || last_name)
ORDERBY last_name
)
),
'/customer_list'
)
ASxml_customers
INTOv_xml_data
FROMcustomers;
-- get thestring value from v_xml_data and store it in v_char_buffer
v_char_buffer:= v_xml_data.GETSTRINGVAL();
-- copy thecharacters from v_char_buffer to the file
UTL_FILE.PUT(v_file, v_char_buffer);
-- flush anyremaining data to the file
UTL_FILE.FFLUSH(v_file);
-- close thefile
UTL_FILE.FCLOSE(v_file);
END write_xml_data_to_file;
/
CREATE PROCEDURE create_xml_resources AS
v_resultBOOLEAN;
-- createstring containing XML for products
v_productsVARCHAR2(300):=
'' ||
'
'
|| ' price="19.95"/>' ||
'
' price="30"/>' ||
'
' price="25.99"/>' ||
'';
-- create string containing XML for producttypes
v_product_types VARCHAR2(300):=
'' ||
'
'
'
'';
BEGIN
-- delete existing resource for products
DBMS_XDB.DELETERESOURCE('/public/products.xml',
DBMS_XDB.DELETE_RECURSIVE_FORCE);
-- create resource for products
v_result :=DBMS_XDB.CREATERESOURCE('/public/products.xml',
v_products);
-- delete exiting resource for product types
DBMS_XDB.DELETERESOURCE('/public/product_types.xml',
DBMS_XDB.DELETE_RECURSIVE_FORCE);
--create resource for product types
v_result :=DBMS_XDB.CREATERESOURCE('/public/product_types.xml',
v_product_types);
ENDcreate_xml_resources;
/
执行如下：
store@PDB1>@xml_examples.sql
Procedurecreated.
Procedurecreated.
调用write_xml_data_to_file如下：
store@PDB1>call write_xml_data_to_file('temp_file_dir','customers.xml');
13. XMLQUERY
store@PDB1> selectxmlquery('(1,2+5,"d",155 to 161,text)' returningCONTENT) as xml_output from dual;
XML_OUTPUT
----------------------------------------------------------------------------------------------------
1 7 d 155 156 157 158 159 160161text