How associate two tables with using xml_id's (unique id) ?

Table1:

table1_id:

id-element-1.2.1.1.3(xml_id)

id-element-1.2.1.1.4(xml_id)

id-element-1.2.1.1.5(xml_id)

Table2

table2_id:

id-element2-1.2.1.1.3.1(xml_id)

id-element2-1.2.1.1.3.2(xml_id)

id-element2-1.2.1.1.4.1(xml_id)

id-element2-1.2.1.1.5.1(xml_id)

I want this result:

Table3:

table1_id table2_id

..3 ..3.1

..3 ..3.2

..4 ..4.1

..5 ..5.1

Thanks