A review of DB2 pureXML initiation

Content Summary:

The DB2 purexml feature allows you to store well-formed XML documents in a hierarchical form in a table column with an XML data type. By storing XML data in an XML column, the data can remain in its native hierarchical form, rather than storing it as text or mapping it to another data model. Because the PureXML data store is fully integrated, the existing DB2 data server features can be used to access and manage stored XML data. storing XML data in its native hierarchical form can make XML search, retrieve, and update more efficient. The combination of XQuery, SQL, or both can be used to query and update XML data. SQL functions that return XML data or take XML arguments, called the Sql/xml function, can also construct or publish XML data based on values retrieved from the database.

Brief introduction

For many years, there are few significant technological innovations in the field of database technology that can cause people to review and rethink the whole database development process. The pureXML technology introduced in the 2006 DB2 9 has made significant innovations in the most basic data organization of relational databases over the past few decades, and for the first time we have looked at the history of databases and the theoretical and external challenges that have underpinned their growth in the past.

Today, we rarely review the history of the database, for the vast majority of it technicians, the database is the same as the relational database, data and table close contact. E-R model is almost the only way we describe the world, SQL language is the only means of database information access processing. Relational databases have become a religious belief, and all the theoretical issues associated with data seem to have been resolved.

However, the development of history has always been a turning point in our inadvertently, all the major technology production and development has its survival soil. 40 years ago the birth of the database is not a relational database, the first generation of the database for the first time to achieve the data management and application of the logic of separation, the use of hierarchical structure to describe the data, is a hierarchical database (IMS). The second generation database was founded on the relational theory and the invention of the SQL language proposed by Dr. E.f Codd in the late 70. It realizes the standardization of data modeling and data manipulation processing, and the relational database has made great progress in the following more than 20 years, and has been widely used. The evolution of technology mainly focuses on the improvement of performance, expansibility and security, and its basic theoretical framework and technical concept have not changed much.

In contrast, in the past more than 20 years, the IT industry has undergone significant changes and a series of technical and conceptual innovation. With the development of the Internet and the interconnection of IT systems in the network environment, the external soil of the database has brought new challenges to the information management technology. In general, there are the following important questions that are difficult to evade:

A diverse world-the complexity of information

Today the complexity of information and the era of relational database theory are not the same, the information structure is increasingly complex, with the demand for personalized service growth, the diversity of information and differences have greatly increased. But the relationship theory is becoming more and more obvious in the management information complexity. E-R model is a two-dimensional model in nature, through a series of two-dimensional relationships to describe complex entity objects, each table represents all the entities in the modeling design, there is no difference, even if only one entity has attributes, you must establish a field for it. So in many systems, we can often see a table with hundreds of fields, and for each record, most of the fields are empty. If the difference between these individuals is not only manifested in the attribute, but also involves the structure and the relationship, it is necessary to establish different tables and corresponding relationships for the entities that have differences. So many of today's business systems often require thousands of tables, or even tens of thousands of of tables. The structure of the database becomes very complex, and the information in the database is difficult to understand.

A variety of information application methods-the comprehensible nature of information

In a sense, today the information of business System database is the by-product of operation system. The database is designed to support the operation of a particular business application, and the data in the database is used only by a single system, so it is rarely considered whether the information is easy to understand. Today, however, more and more systems need to collaborate and share information. The readability of information is becoming increasingly important if it is easy to understand. Relational database has a great shortage in this aspect, the data in the table can not describe itself, and the relationship between tables can not be directly reflected in the data. Which makes many systems that