请问以下两个执行计划那个更好？

[pennyzhueng]

请问以下两个执行计划那个更好？
其中item_safety表有100万数据，safety_type大概有20条数据
I_SAFETY_ID 是ITEM_SAFETY表的索引，字段：safety_id关联SAFETY_TYPE表

SELECT STATEMENT, GOAL = CHOOSE
SORT GROUP BY
TABLE ACCESS BY INDEX ROWID Object owner=DEV Object name=ITEM_SAFETY
NESTED LOOPS
TABLE ACCESS FULL Object owner=DEV Object name=SAFETY_TYPE
INDEX RANGE SCAN Object owner=DEV Object name=I_SAFETY_ID
SELECT STATEMENT, GOAL = CHOOSE
SORT GROUP BY
NESTED LOOPS
TABLE ACCESS FULL Object owner=DEV Object name=ITEM_SAFETY
TABLE ACCESS BY INDEX ROWID Object owner=DEV Object name=SAFETY_TYPE
INDEX UNIQUE SCAN Object owner=DEV Object name=PK_SAFETY_TYPE

[doulikeme]

应该是前面的快，比较item_safety有100w的数据，做全表扫描是很慢的 而且又是在 nested loops里面

[tyrone98]

与你返回记录数有关,返回少第一个好,返回少第二个好.oracle的执行计划找出来的应当就是在现有数据前提下是最优的,当然前提是你有做好了表分析.

[nicolas1999king]

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