Getting Startedwith pureQuery

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Getting Started with pureQuery
create a query that exposes the XML data in relational format and XQuery transform
expressions are used to persist updates back into the XML data stored in the database.
Figure 15.1 - Giving control to the SQL layer
Figure 15.1 shows a high level view of this approach. When reading data from the
database, an SQL/XML statement containing an XMLTABLE() function is used to expose
the XML data in relational format. The relational data rows are then interpreted by the
pureQuery API, which uses them to populate the Java beans in the application layer. The
SQL/XML statement used to do this mapping can be seen in Listing 16.1:
public static void updateEmployee(Data data, Employee emp){
String sql = "update employee set doc = xmlquery(" +
"'copy $new := $DOC " +
"modify (do replace value of $new/employee/name/first with
$firstname," +
"do replace value of $new/employee/name/last with $lastname," +
"do replace value of $new/employee/office with $office)" +
"return $new' " +
"passing cast(:firstname as varchar(20)) as \"firstname\", " +
"cast(:lastname as varchar(20)) as \"lastname\"," +
"cast(:office as INTEGER) as \"office\"" +
") where id = :id";
data.update(sql, emp);
}
Listing 15.1 – SQL/XML Mapping
You can use SQL/XML statements in either style of pureQuery programming: inline style or
annotated method style. Please refer to Chapters 5 and 6 to learn more about these two
different styles of programming with the pureQuery API.
When persisting changes into the database, the pureQuery API fetches the updated values
from the Java beans and passes them into the database, where an XQuery Transform