THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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Assume we have the following XML document:
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| Code Block | ||
|---|---|---|
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<?xml version="1.0" encoding="UTF-8"?> |
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<root> |
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<organization type="governmental"> |
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<name>Company A</name> |
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<employees> |
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<employee> |
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<name>John Doe</name> |
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<gender>M</gender> |
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</employee> |
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<employee> |
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<name>Jane Doe</name> |
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<gender>F</gender> |
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</employee> |
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</employees> |
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</organization> |
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<organization type="company"> |
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<name>Company B</name> |
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<employees> |
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<employee> |
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<name>Peter</name> |
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<gender>M</gender> |
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</employee> |
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<employee> |
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<name>Bob</name> |
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<gender>M</gender> |
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</employee> |
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</employees> |
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</organization> |
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</root> |
Now imagine that you want to have a table of employee names and gender information, and another table with company name and type information. We define our DataContext and those tables like this:
| Code Block | ||
|---|---|---|
| ||
XmlSaxTableDef employeeTableDef = new XmlSaxTableDef(
"/root/organization/employees/employee",
new String[] {
"/root/organization/employees/employee/name",
"/root/organization/employees/employee/gender"
}
);
XmlSaxTableDef organizationTableDef = new XmlSaxTableDef(
"/root/organization",
new String[] {
"/root/organization/name",
"/root/organization@type"
}
);
DataContext dc = new XmlSaxDataContext(new File("my_file.xml"), employeeTableDef, organizationTableDef); |
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row_id | /name | /gender | index(/root/organization) |
|---|---|---|---|
| 0 | John Doe | M | 0 |
| 1 | Jane Doe | F | 0 |
| 2 | Peter | M | 1 |
| 3 | Bob | M | 1 |
Moving on, you will be able to define both joins and lookups using this foreign key. For example:
| Code Block | ||
|---|---|---|
| ||
Column fk = employeeTable.getColumnByName("index(/root/organization)");
Column empName = employeeTable.getColumnByName("/name");
Column orgId = organizationTable.getColumnByName("row_id");
Column orgName = organizationTable.getColumnByName("/name");
Query q = dc.query().from(employeeTable)
.innerJoin(organizationTable).on(fk, orgId)
.select(empName).as("employee")
.select(orgName).as("company").toQuery();
DataSet ds = dc.executeQuery(q); |
The contents of this queried dataset will now be:
employee | company |
|---|---|
| John Doe | Company A |
| Jane Doe | Company A |
| Peter | Company B |
| Bob | Company B |