4-2-2. Index Only Scan vs. Index Scan

-- [SQL-4-2-2-a] EXPLAIN (ANALYZE,BUFFERS,COSTS OFF) SELECT t1.ord_dtm FROM startdbpg.tr_ord_big t1 WHERE t1.ord_dtm >= '2023-03-01'::date AND t1.ord_dtm < '2023-03-03'::date;

-- [SQL-4-2-2-b] EXPLAIN (ANALYZE,BUFFERS,COSTS OFF) SELECT t1.ord_dtm ,t1.ord_no FROM startdbpg.tr_ord_big t1 WHERE t1.ord_dtm >= '2023-03-01'::date AND t1.ord_dtm < '2023-03-03'::date;