[web2py] how to "orderby" string field with multiple words by second word

[Andriy]

I have a table with 'name' Field:
db.define_table('person', Field('name', 'string'))

'name' is in format 'Name Lastname', ie, "Mark Twain". Can I sort such 
records by Lastname when selecting with "orderby"? Like this: 
db(db.person).select(db.person.name, orderby=?) 

I thought about writing lambda with db.person.name.split(' ', [-1]) but can 
not figure it out...

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