TAILIEUCHUNG - SQL Clearly Explained- P8

SQL Clearly Explained- P8: You don’t need to be a database designer to use SQL successfully. However, you do need to know a bit about how relational databases are structured and how to manipulate those structures. | The XML Data Type 361 SELECT FROM xmlstuff produces sequ_numb xml_text ----------- ------------------ 1 this is a test Note You could store XML in a text column tags and all. However when you use an XML column SQL will check the XML to see that it is well-formed. The XMLSERIALIZE function is essentially the opposite of XMLSERIALIZE XMLPARSE It takes the contents of an XML column and converts it to a text string XMLSERIALIZE type_indicator column_name AS character_type For example SELECT XMLSERIALIZE DOCUMENT xmltext AS VARCHAR 256 FROM sql_stuff WHERE seq_numb 16 would extract the document from the row with the sequence number of 16 convert it to plain text removing the tags and display it on the screen. Because SQL removes the tags from interactive SELECT output this function is particularly useful in an embedded SQL program. Please purchase PDF Split-Merge on to remove this watermark. The ObjectRelational Data Model The relational data model has been a mainstay of business data processing for nearly 30 years. Nothing has superseded it in the way the relational data model superseded the simple network data model. However a newer data model the object-oriented data model1 has come into use as an alternative for some types of navigational data processing. This chapter presents an overview of some object-oriented concepts for readers who aren t familiar with the object-oriented paradigm. Chapter 19 looks at the SQL standard s support for object-oriented structures. If you have object-oriented programming experience then you can skip over the first parts of this chapter and begin reading with the section Pure Object-Oriented Databases. The object-oriented paradigm was the brainchild of Dr. Kristen Nygaard a Norwegian who was attempting to write a computer program to model the behavior of ships tides and fjords. He found that the interactions were extremely complex and realized that it would be easier to write the program if he 1 To be completely .

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