[MonetDB-users] sorting on multiple attributes in MIL

just a short MIL question: I have a table <attr1 | attr2 | attr3> vertically fragmented into three BATs. Now I would like to get the the table sorted on both attr1, attr2, like this: attr1 attr2 attr3 1 1 0.2 1 2 0.3 2 1 0.4 2 3 0.1 How do I do this with the 3 BATs in MIL. Does anyone has an example MIL code of such an operation?