<xs:complexType name="book">
    <xs:sequence>
        <xs:element name = "bookName" nillable="true" minOccurs="0">
            <xs:simpleType>
                <xs:restriction base="xs:string"
                </xs:restriction>
            </xs:simpleType>
        </xs:element>
        <xs:element name = "bookPrice" nillable="true" minOccurs="0">
            <xs:simpleType>
                <xs:restriction base="xs:decimal"
                </xs:restriction>
            </xs:simpleType>
        </xs:element>
        <xs:attribute name="bookId" type="xs:ID" use="required"/>
</xs:complexType>

<xs:complexType name="book">
    <xs:sequence>
        <xs:element name = "bookName" nillable="true" minOccurs="0">
            <xs:simpleType>
                <xs:restriction base="xs:string">
            </xs:simpleType>
            <xs:unique name="uniqueBookName">
                <xs:selector xpath="book"/>
                <xs:field xpath="bookName"/>
            </xs:unique>
        </xs:element>
        <xs:element name = "bookPrice" nillable="true" minOccurs="0">
            <xs:simpleType>
                <xs:restriction base="xs:decimal"
                </xs:restriction>
            </xs:simpleType>
        </xs:element>
        <xs:attribute name="bookId" type="xs:ID" use="required"/>
</xs:complexType>