# subscript_operator - PostgreSQL
docker run --rm postgres:latest su postgres -c \
  "initdb -D /tmp/d >/dev/null 2>&1 && pg_ctl start -D /tmp/d -l /tmp/l -o '-k /tmp' >/dev/null 2>&1 && sleep 2 && psql -h /tmp -t -c \"
    SELECT (ARRAY[1,2,3])[2], (ARRAY[1,2,3])[0], (ARRAY[1,2,3])[5], (ARRAY[1,2,3])[-1];
  \""
# Output: 2 | | |
# (empty = NULL)

# subscript_operator - CockroachDB
docker run --rm cockroachdb/cockroach:latest demo --no-example-database --insecure -e "
  SELECT (ARRAY[1,2,3])[2], (ARRAY[1,2,3])[0], (ARRAY[1,2,3])[5], (ARRAY[1,2,3])[-1];
" 2>&1 | tail -3
# Output: 2 | NULL | NULL | NULL

# index_of - PostgreSQL
docker run --rm postgres:latest su postgres -c \
  "initdb -D /tmp/d >/dev/null 2>&1 && pg_ctl start -D /tmp/d -l /tmp/l -o '-k /tmp' >/dev/null 2>&1 && sleep 2 && psql -h /tmp -t -c \"
    SELECT array_position(ARRAY[1,2,3], 2), array_position(ARRAY[1,2,3], 5);
  \""
# Output: 2 |
# (empty = NULL for not found)

# index_of - DuckDB
docker run --rm duckdb/duckdb:latest duckdb -noheader -list -c "
  SELECT list_position([1,2,3], 2), list_position([1,2,3], 5);
"
# Output: 2|NULL

# index_of - CockroachDB  
docker run --rm cockroachdb/cockroach:latest demo --no-example-database --insecure -e "
  SELECT array_position(ARRAY[1,2,3], 2), array_position(ARRAY[1,2,3], 5);
" 2>&1 | tail -3
# Output: 2 | NULL