Viewing relational data as XML Using Microsoft SQL Server

The ”FOR XML” clause SELECT comes with a ”FOR XML” clause Example – SELECT * FROM student FOR XML RAW; – Output is an XML document 2Viewing relational data as XML

Formatting options The XML output can be formatted in different ways – RAW – AUTO – EXPLICIT – PATH 3Viewing relational data as XML

RAW formatting Each row in the output becomes an XML element. – Element name is ’row’ – Table column names used as XML attribute names Example, simple – SELECT * FROM student FOR XML RAW; – Output Example, join SELECT d.departmentID, departmentName, teachername FROM department d join teacher t ON d.departmentID = t.departmentID FOR XML RAW – Output No hierarchy! 4Viewing relational data as XML

AUTO formatting Each row in the output becomes an XML element. – Table name used as XML element name Example, simple – SELECT * FROM student FOR XML AUTO; – Output Example, join SELECT d.departmentID, departmentName, teachername FROM department d join teacher t ON d.departmentID = t.departmentID FOR XML AUTO – Output … 5Viewing relational data as XML

EXPLICIT formatting Gives you a lot of control over the output – Element names, attribute names, etc. Requires a lot of work! Not used very often May soon be deprecated Viewing relational data as XML6

PATH formatting A better way of doing EXPLICIT Used for complex XML output Based on XPath Example, simple – SELECT * FROM student FOR XML PATH; – Output 1 John Each row becomes an element (like RAW) Each column becomes a child-element (unlike RAW) Viewing relational data as XML7

PATH formatting, continued Example – SELECT studentID as studentname FROM student FOR XML PATH; – Output John Liz Columns becomes attributes in the XML output And much more XPath stuff … Viewing relational data as XML8