# Pastebin jk9eqzHy
$ perl6 -Ilib -e '

use Red;

model M is table<mmm> { has Str $.a is column; has Bool $.b is column; has Int $.c is column }
my $*RED-DB = database "SQLite";
M.^create-table;
M.^all.map: { next unless .b; .c ?? .c !! .a }
'
{{mmm.c => False, mmm.b => False} => next, {mmm.c => False, mmm.b => True} => mmm.a, {mmm.c => True, mmm.b => True} => mmm.c}