从上面结果可以看出，在为绑定变量传入第一个值为13871时，由于返回的记录条数较少，导致走索引扫描。当我们第二次传入绑定变量值1时，oracle不再生成新的执行计划，而直接拿索引扫描的执行路径来用。
但是，如果先传入1的绑定变量值，然后再传入13871的绑定变量值时，会怎样？我们继续测试。
hr@ora10g> alter system flush shared_pool; hr@ora10g> set autotrace traceonly exp stat; hr@ora10g> exec :v_id := 1; hr@ora10g> select * from t1 where id=:v_id; hr@ora10g > begin 2 select sql_id into :v_sql_id from v$sql 3 where sql_text like 'select * from t1 where id=:v_id%'; 4 end; 5 / hr@ora10g > select * from table(dbms_xplan.display_cursor(:v_sql_id)); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- SQL_ID djwq30cpbcz7k, child number 0 ------------------------------------- select * from t1 where id=:v_id Plan hash value: 3617692013 -------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 13 (100)| | |* 1 | TABLE ACCESS FULL | T1 | 8738 | 179K | 13 (0) | 00:00:01 | -------------------------------------------------------------------------- ...... hr@ora10g > exec :v_id := 13871; hr@ora10g > select * from t1 where id=:v_id; hr@ora10g > begin 2 select sql_id into :v_sql_id from v$sql 3 where sql_text like 'select * from t1 where id=:v_id%'; 4 end; 5 / hr@ora10g > select * from table(dbms_xplan.display_cursor(:v_sql_id)); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- SQL_ID djwq30cpbcz7k, child number 0 ------------------------------------- select * from t1 where id=:v_id Plan hash value: 3617692013 -------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 13 (100)| | |* 1 | TABLE ACCESS FULL | T1 | 8738 | 179K | 13 (0) | 00:00:01 | ----------