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oracle联表查询速度奇慢，大约要30秒；每个表的数据20万左右；关联索引已经都建了；
有哪位高手帮忙指点下，万分感谢！
select count(a.ID) from scene_investigation a,scene_law_case b where a.del
ete_flag=1 and b.delete_flag=0 and a.CASe_id=b.ID;

Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=2762 Card=1 Bytes=66
)

1 0 SORT (AGGREGATE)
2 1 MERGE JOIN (Cost=2762 Card=99686 Bytes=6579276)
3 2 TABLE ACCESS (BY INDEX ROWID) OF 'SCENE_INVESTIGATION'
(Cost=826 Card=99686 Bytes=3289638)

4 3 INDEX (FULL SCAN) OF 'INDEX_SCENE_CASE_ID' (NON-UNIQ
UE) (Cost=26 Card=199372)

5 2 SORT (JOIN) (Cost=1936 Card=199344 Bytes=6578352)
6 5 TABLE ACCESS (FULL) OF 'SCENE_LAW_CASE' (Cost=706 Ca
rd=199344 Bytes=6578352)



Statistics
----------------------------------------------------------
0 recursive calls
7 db block gets
73004 consistent gets
28954 physical reads
0 redo size
406 bytes sent via SQL*Net to client
503 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
1 sorts (disk)
1 rows processed