[web2py] dynamic queries

[dave]

I have something like    
    qset=db()
    if arg1 == "xyz": qset=qset(db.abc.id > 0)
    if arg2 == "abc": qset=qset(db.abc.age > 5)
    returned = qset.select()
    return SQLFORM.grid(returned)

qset.select returns all the rows with all the columns I think, I know that 
SQLFORM.grid accepts a table or a query so how can I pass this to it?

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