The definitions of the columns used in SQL are as follows.
TBL_SHA ms_cd character(6) NOT NULL -- PRIMARY KEY et_cd character(8) etrys character(8) TBL_INF ms_cd character(6) NOT NULL -- PRIMARY KEY ry_cd character(8) NOT NULL -- PRIMARY KEY I made some modifications to the data, and I realized that I should not change the length of the data. The actual data and its corresponding execution plan are shown below. explain analyze select COUNT(ET_CD) from TBL_SHA WHERE TBL_SHA.MS_CD = 'MLD009' and TBL_SHA.ETRYS in (select TBL_INF.RY_CD from TBL_INF WHERE TBL_INF.MS_CD = 'MLD009' AND TBL_INF.RY_CD = '00000001' ) ----- Execution Plan ----- Limit (cost=2738709.57..2738709.58 rows=1 width=8) (actual time=124168.769..124168.771 rows=1 loops=1) -> Aggregate (cost=2738709.57..2738709.58 rows=1 width=8) (actual time=124168.767..124168.769 rows=1 loops=1) -> Nested Loop (cost=0.29..2730702.63 rows=3202774 width=9) (actual time=97264.166..123920.769 rows=3200000 loops=1) -> Index Only Scan using TBL_INF_pkc on TBL_INF (cost=0.29..8.31 rows=1 width=9) (actual time=0.025..0.030 rows=1 loops=1) Index Cond: ((MS_CD = 'MLD009'::bpchar) AND (RY_CD = '00000001'::bpchar)) Heap Fetches: 1 -> Seq Scan on TBL_SHA (cost=0.00..2698666.58 rows=3202774 width=18) (actual time=97264.138..123554.792 rows=3200000 loops=1) Filter: ((MS_CD = 'MLD009'::bpchar) AND (ETRYS = '00000001'::bpchar)) Rows Removed by Filter: 32000325 Planning Time: 0.162 ms Execution Time: 124168.838 ms At 2023-07-20 22:48:19, "Laurenz Albe" <laurenz.a...@cybertec.at> wrote: >On Thu, 2023-07-20 at 22:14 +0800, gzh wrote: >> The information I provided is incorrect, please see my previous reply. > >My question remains: I would like to see the table definitions. > >Also, did you ANALYZE the tables? > >Yours, >Laurenz Albe