我的一个sql单从执行计划来看很好,但是运行起来效率很差。后来看数据发现IDX_PROBPRN_REGION_CODE的结果集很大,NESTED LOOPS用在这里就会很慢。听说过这种情况下用MERGE JOIN会很高效,但是我不清楚hint怎么指定使用MERGE JOIN。请高人指点一下,谢谢啦!SELECT STATEMENT, GOAL = CHOOSE
SORT UNIQUE
NESTED LOOPS
NESTED LOOPS
TABLE ACCESS BY INDEX ROWID Object owner=LIFEREPT Object name=PROBPRN
INDEX RANGE SCAN Object owner=LIFEREPT Object name=IDX_PROBPRN_REGION_CODE
TABLE ACCESS BY INDEX ROWID Object owner=LIFEREPT Object name=PROBPRN_TRACE
INDEX RANGE SCAN Object owner=LIFEREPT Object name=IDX_PROBPRN_TRACE
TABLE ACCESS BY INDEX ROWID Object owner=LIFEREPT Object name=PROBPRN_DESC
INDEX RANGE SCAN Object owner=LIFEREPT Object name=IDX_PROBPRN_DESC
SORT UNIQUE
NESTED LOOPS
NESTED LOOPS
TABLE ACCESS BY INDEX ROWID Object owner=LIFEREPT Object name=PROBPRN
INDEX RANGE SCAN Object owner=LIFEREPT Object name=IDX_PROBPRN_REGION_CODE
TABLE ACCESS BY INDEX ROWID Object owner=LIFEREPT Object name=PROBPRN_TRACE
INDEX RANGE SCAN Object owner=LIFEREPT Object name=IDX_PROBPRN_TRACE
TABLE ACCESS BY INDEX ROWID Object owner=LIFEREPT Object name=PROBPRN_DESC
INDEX RANGE SCAN Object owner=LIFEREPT Object name=IDX_PROBPRN_DESC
不清楚什么问题了