XSD Tutorials - Herong's Tutorial Examples - Version 5.10, by Dr. Herong Yang

Identity-Constraints: unique, key and keyref

This chapter provides notes and tutorial examples on identity constraints. Topics include introduction of 'unique', 'key' and 'keyref' identify constraints; XML and XSD examples of using identity constraints.

What Are Identity-Constraints?

What Is "unique" Identity-Constraint?

What Is "key" Identity-Constraint?

What Is "keyref" Identity-Constraint?

"keyref" Identity-Constraint XSD Example

Identity-Constraint with Multiple Fields

Conclusion:

  • A "unique" identify constraints on repeating sub elements is like a UNIQUE constraint in a database table. Values must be unique, if exist.
  • A "key" identify constraints on repeating sub elements is like a PRIMARY KEY constraint in a database table. Values must exist and be unique.
  • A "keyref" identify constraints on repeating sub elements is like a FOREIGN KEY constraint in a database table. Values must exist and refer to values of another "key" identity constraint.

Table of Contents

 About This Book

 Introduction to XML Schema

 XML Editor and Schema Processor - XMLPad

 Java API for XML Processing - JAXP

 JAXP - XML Schema (XSD) Validation

 Xerces2 Java Parser - Java API of XML Parsers

 Using Xerces2 Java API

 XML Schema Language - Basics

 Introduction of XSD Built-in Datatypes

 "string" and Its Derived Datatypes

 "decimal" and Its Derived Datatypes

 "dateTime" and Its Related Datatypes

 Miscellaneous Built-in Datatypes

 Facets, Constraining Facets and Restriction Datatypes

 "simpleType" - Defining Your Own Simple Datatypes

 Complex Element Declaration

Identity-Constraints: unique, key and keyref

 Assertion as Custom Validation Rules

 XML Schema Location and Namespace in XML Documents

 Overriding Element Types in XML Documents

 Linking Multiple Schema Documents Together

 Glossary

 References

 PDF Printing Version

Identity-Constraints: unique, key and keyref - Updated in 2014, by Dr. Herong Yang