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分类: Oracle
2025-01-22 09:09:36
explain select max(id),min(id) from main_t; QUERY PLAN ---------------------------------------------------------------------------------------------------------- Result (cost=0.64..0.65 rows=1 width=8) InitPlan 1 (returns $0) -> Limit (cost=0.28..0.32 rows=1 width=4) -> Index Only Scan Backward using idx1_main_t on main_t (cost=0.28..45.77 rows=1000 width=4) Index Cond: (id IS NOT NULL) InitPlan 2 (returns $1) -> Limit (cost=0.28..0.32 rows=1 width=4) -> Index Only Scan using idx1_main_t on main_t main_t_1 (cost=0.28..45.77 rows=1000 width=4) Index Cond: (id IS NOT NULL) (9 rows) |
explain analyze select max(id),min(id) from main_t\G *************************** 1. row *************************** EXPLAIN: -> Rows fetched before execution (cost=0.00..0.00 rows=1) (actual time=0.000..0.000 rows=1 loops=1) |
select max(id),min(id) from main_t; Elapsed: 00:00:00.01 Execution Plan ---------------------------------------------------------- Plan hash value: 3205363217 ----------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ----------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 4 | 9 (0)| 00:00:01 | | 1 | SORT AGGREGATE | | 1 | 4 | | | | 2 | TABLE ACCESS FULL| MAIN_T | 10000 | 40000 | 9 (0)| 00:00:01 | ----------------------------------------------------------------------------- select max(id) from main_t; Elapsed: 00:00:00.00 Execution Plan ---------------------------------------------------------- Plan hash value: 2290008741 ----------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ----------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 4 | 2 (0)| 00:00:01 | | 1 | SORT AGGREGATE | | 1 | 4 | | | | 2 | INDEX FULL SCAN (MIN/MAX)| IDX_MAIN_T | 1 | 4 | 2 (0)| 00:00:01 | ----------------------------------------------------------------------------------------- |
select (select max(id) from main_t) max_id,(select min(id) from main_t) min_id from dual; Execution Plan ---------------------------------------------------------- Plan hash value: 3605433664 ----------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ----------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 6 (0)| 00:00:01 | | 1 | SORT AGGREGATE | | 1 | 4 | | | | 2 | INDEX FULL SCAN (MIN/MAX)| IDX_MAIN_T | 1 | 4 | 2 (0)| 00:00:01 | | 3 | SORT AGGREGATE | | 1 | 4 | | | | 4 | INDEX FULL SCAN (MIN/MAX)| IDX_MAIN_T | 1 | 4 | 2 (0)| 00:00:01 | | 5 | FAST DUAL | | 1 | | 2 (0)| 00:00:01 | ---------------------------- |