Best way to check boolean value

Question

Hi!
I have a schema defining an XML element with a boolean attribute. The document related to this schema use true/false literal boolean values, eg:
<myelement myattribute="false"/>....<myelement myattribute="true"/>
The data is stored in binary xml storage.
I query the db on the boolean attribute with an xpath condition like this:
..../myelement[@myattribute=false()]
Querying the db with this method:
SELECT XMLQuery('....' returning content) from dual
all works as expected.
Instead, using:
SELECT XMLQuery('....' ' PASSING OBJECT_VALUE RETURNING CONTENT)
FROM "myxmltable"
WHERE XMLExists('....' PASSING OBJECT_VALUE);
I get the error: ORA-31038: Invalid hexBinary value: "false"
To get the second query method working, I have to change the xpath condition, forcing a string comparison:
..../myelement[string(@myattribute)="false"]
Can someone explain me this behaviour? What is the best way to check a boolean value? I'd like to write the same xquery working in both methods!
Thank you.
Bye
Mirko

Answer 1

Hi Geoff
here the schema:
<xs:schema xmlns:tns="http://OracleTest" xmlns:xdb="http://xmlns.oracle.com/xdb" elementFormDefault="qualified" targetNamespace="http://OracleTest" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:complexType name="MyComplexType">
<xs:sequence>
<xs:element minOccurs="0" name="FirstChild">
<xs:complexType>
<xs:attribute name="A" type="xs:string" />
<xs:attribute name="B" type="xs:string" />
</xs:complexType>
</xs:element>
<xs:element minOccurs="0" name="SecondChild">
<xs:complexType>
<xs:attribute name="S" type="xs:string" />
<xs:attribute name="B" type="xs:boolean" />
<xs:attribute name="I" type="xs:integer" />
</xs:complexType>
</xs:element>
<xs:element minOccurs="0" name="ThirdChild">
<xs:complexType>
<xs:sequence>
<xs:element minOccurs="0" name="ThirdChildA">
<xs:complexType>
<xs:attribute name="A" type="xs:string" />
<xs:attribute name="B" type="xs:string" />
</xs:complexType>
</xs:element>
<xs:element minOccurs="0" name="ThirdChildB">
<xs:complexType>
<xs:attribute name="C" type="xs:string" />
<xs:attribute name="D" type="xs:string" />
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="ID" type="xs:string" />
</xs:complexType>
<xs:element xdb:defaultTable="MyElement" name="MyElement" type="tns:MyComplexType" />
</xs:schema>
and here two sample XML documents:
<tns:MyElement ID="ID1" xmlns:tns="http://OracleTest" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://OracleTest http://OracleTest.xsd">
<tns:FirstChild A="a" B="b" />
<tns:SecondChild S="s" B="true" I="1" />
<tns:ThirdChild>
<tns:ThirdChildA A="aa" B="bb" />
<tns:ThirdChildB C="cc" D="dd" />
</tns:ThirdChild>
</tns:MyElement>
<tns:MyElement ID="ID2" xmlns:tns="http://OracleTest" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://OracleTest http://OracleTest.xsd">
<tns:FirstChild A="aa" B="bb" />
<tns:SecondChild S="ss" B="false" I="2" />
<tns:ThirdChild>
<tns:ThirdChildA A="aaaa" B="bbbb" />
<tns:ThirdChildB C="cccc" D="dddd" />
</tns:ThirdChild>
</tns:MyElement>
I registered the schema using Enterprise Manager. The "Show SQL" function returned this script:
BEGIN
DBMS_XMLSCHEMA.REGISTERSCHEMA(
schemaurl => 'http://OracleTest.xsd',
schemadoc => sys.UriFactory.getUri('/Testing/test.xsd'),
local => FALSE,
gentypes => FALSE,
genbean => FALSE,
gentables => TRUE,
force => FALSE,
owner => 'EMILIAROMAGNABUY',
OPTIONS => DBMS_XMLSCHEMA.REGISTER_BINARYXML);
END;
This is my test script:
-- This works fine: returns only the requested row.
SELECT XMLQuery('declare default element namespace "http://OracleTest"; collection("/Testing")/MyElement/SecondChild[@B=true()]' returning content) from dual;
-- This raises the error = SQL Error: ORA-31038: Invalid hexBinary value: "true"
select xmlquery('declare default element namespace "http://OracleTest"; /MyElement/SecondChild[@B=true()]' passing object_value returning content).getclobval() from "MyElement";
-- This doesn't work correctly: returns the requested row and two empty rows ?!? I don't like this cast, anyway.
select xmlquery('declare default element namespace "http://OracleTest"; /MyElement/SecondChild[string(@B)="true"]' passing object_value returning content).getclobval() from "MyElement";
Thank you
Mirko