// q

t:([n:key 10];p:0 0 0 2 2 2 4 4 7 7;d:10?100)           / tree (as key table)
t:update d:0N from t where n in p                       / null out non-leaves

f:50<                                                   / predicate

s:select from t where
  n in distinct raze((exec p from t)scan)each 
  exec n from t where f d                               / select subtree

\

q)s
n| p d
-| ----
0| 0
1| 0 67
2| 0
3| 2 73
4| 2
6| 4 53
7| 4
8| 7 83