Description of the illustration lead_lag_clause.eps
HIERARCHY hierarchy_ref OFFSET offset_expr [ { WITHIN { LEVEL | PARENT } | ACROSS ANCESTOR AT LEVEL level_ref [ POSITION FROM { BEGINNING | END } } ]
HIERARCHY hierarchy_ref OFFSET offset_expr [ { WITHIN { LEVEL | PARENT } | ACROSS ANCESTOR AT LEVEL level_ref [ POSITION FROM { BEGINNING | END } } ]