How
to Access a Database Using XML Delivering
XML with Data Depending
upon the applications, there are two methods of using XML data as a communication
platform between a client and server.
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1. Using the database engine to generate the XML data.
2. Using middleware
systems to convert to/from XML and the legacy infrastructure. Database
created XML, to only incorporate data contained within the data base. It is difficult
to flexibly represent some data, because they deal with individual rows and not
hierarchical data. The data that does not change frequently, the XML data is generated
only upon changes, and not the client requests. If data mining is a requirement,
the real solution is generating the XML data from the SQL server, because there
are only few tools for OLAP processing in the middleware realm. Middleware
computing provides a central point of access to many systems, database driven
or not. Middleware also performs rules based processing
on data that is being
translated. The middleware approach is expensive to build and may be overkill
for a specific application. It is slower than database created XML for data that
is not changing frequently. Retrieving
Data from SQL database There
are two different methods of generating XML from within SQL server. One way is
to use Web Assistant Wizard, to create Web Tasks, which are automated tasks that
run at specific intervals and generate either HTML or XML files, or the second
way is to use stored procedures to return results sets that are formatted into
XML. Also
using Web Assistant Wizard it is possible to create Web Task that generates the
XML file that retrieves the data from SQL database and displays it in the browser. Microsoft’s
SQL feature is to make the generation of HTML files from SQL. There is no reason
to build custom Web software that interactively queries for the data and builds
HTML results. Web Tasks are designed and are meant to generate an HTML. An XML
specification is not complete when Web Tasks are added to SQL server. Web
Tasks automatically creates the XML file based on the template created by the
user and the settings given in the Web Assistant Wizard. The XML files retrieves
the data from SQL Server and displays it to the user and viewed from the browser.
To access the database using XML, an example is given below. A
table is created called “Bookinfo“ with the columns BName, Author, AuthorADD,
Phone, Publisher and PublisherADD in SQL Server database and insert rows. A template
file called “Bookinfo.tpl” is also created and the Web Assistant Wizard
is used to create the Bookinfo.xml file. The
real flexibility of the template feature of SQL Server is the ability to use it
to generate XML. The server does not care whether the file contains all anything
other than the keywords it uses to insert current row data. Three files,one the
template file called Bookinfo.tpl, one the DTD file called the Bookinfo.dtd and
one CSS file called Bookinfo.css. The
CSS file contains the codes for styling format. The keywords <%begindetail%>,
<%enddetail%> and <%insert_data_here%> are the ASP code used to fetch
the data from SQL database. <%begindetail%> and <%endetail%> are used
to mark the area where SQL query’s results set should be used to fill the
<%insert_data_here%> statements. It indicates where column data should be
placed from the results set. The following is the code for Bookinfo.tpl. <?xml
version=”1.0”?>
<?xml-stylesheet href=”Bookinfo.css”
type=”text/css”?>
<!doctype penta SYSTEM “Bookinfo.dtd”>
<penta>
<pentabody>
<toptitle>Online
books dot com</toptitle>
<weltext>Welcome to online books</weltext>
<bodytext>Happy
to inform the facility of reading the following books online at free of cost</bodytext>
</pentabody>
<Bookinfo>
<%begindetail%>
<Entry>
<BName
><%insert_data_here%></BName>
<Author><%insert_data_here%></Author>
<AuthorADD><%insert_data_here%></AuthorADD>
<Phone><%insert_data_here%></Phone>
<Publisher><%insert_data_here%></Publisher>
<PublisherADD><%insert_data_here%></PublisherADD>
</Entry>
<%enddetail%>
</Bookinfo>
<Foot>
<Footer>Online
books for demonstration</footer>
</Foot>
</penta> The
following is the code for Bookinfo.dtd <!ELEMENT
penta (pentabody, Bookinfo, Foot)>
<!ELEMENT pentabody (toptitle, weltext,
bodytext)>
<!ELEMENT toptitle (#PCDATA)>
<!ELEMENT welltext
(#PCDATA)>
<!ELEMENT bodytext (#PCDATA)>
<!ELEMENT Bookinfo
(Entry)>
<!ELEMENT Entry (BName, Author, AuthorADD, Phone, Publisher,
PublisherADD)>
<!ELEMENT BName (#PCDATA)>
<!ELEMENT Author
(#PCDATA)>
<!ELEMENT AuthorADD (#PCDATA)>
<!ELEMENT Phone
(#PCDATA)>
<!ELEMENT Publisher (#PCDATA)>
<!ELEMENT PublisherADD
(#PCDATA)>
<!ELEMENT Foot (#PCDATA)>
<!ELEMENT Footer (#PCDATA)
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