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数据库版本11g

select * From emp where ename='SMITH' or empno=7902SQL>      select * from table(dbms_xplan.display_cursor('5gj2f75x9xtnx')); PLAN_TABLE_OUTPUT--------------------------------------------------------------------------------SQL_ID  5gj2f75x9xtnx, child number 0-------------------------------------select * From emp where ename='SMITH' or empno=7902Plan hash value: 962431618--------------------------------------------------------------------------------| Id  | Operation                        | Name          | Rows  | Bytes | Cost--------------------------------------------------------------------------------|   0 | SELECT STATEMENT                 |               |       |       |     8|   1 |  TABLE ACCESS BY INDEX ROWID     | EMP           |     2 |    78 |     8|   2 |   BITMAP CONVERSION TO ROWIDS    |               |       |       ||   3 |    BITMAP OR                     |               |       |       ||   4 |     BITMAP CONVERSION FROM ROWIDS|               |       |       ||*  5 |      INDEX RANGE SCAN            | I_EMP         |       |       |     1|   6 |     BITMAP CONVERSION FROM ROWIDS|               |       |       ||*  7 |      INDEX RANGE SCAN            | SYS_C00182518 |       |       |     0--------------------------------------------------------------------------------Predicate Information (identified by operation id): PLAN_TABLE_OUTPUT-----------------------------------------------------------------------------------------------------------------------------------   5 - access("ENAME"='SMITH')   7 - access("EMPNO"=7902) select /*+ USE_CONCAT */* From emp where ename='SMITH' or empno=7902SQL>      select * from table(dbms_xplan.display_cursor('61agkrn33a0z1')); PLAN_TABLE_OUTPUT--------------------------------------------------------------------------------SQL_ID  61agkrn33a0z1, child number 0-------------------------------------select /*+ USE_CONCAT */* From emp where ename='SMITH' or empno=7902Plan hash value: 3488550714--------------------------------------------------------------------------------| Id  | Operation                    | Name          | Rows  | Bytes | Cost (%CP--------------------------------------------------------------------------------|   0 | SELECT STATEMENT             |               |       |       |     3 (10|   1 |  CONCATENATION               |               |       |       ||   2 |   TABLE ACCESS BY INDEX ROWID| EMP           |     1 |    39 |     1   (|*  3 |    INDEX UNIQUE SCAN         | SYS_C00182518 |     1 |       |     0   (|*  4 |   TABLE ACCESS BY INDEX ROWID| EMP           |     1 |    39 |     2   (|*  5 |    INDEX RANGE SCAN          | I_EMP         |     1 |       |     1   (--------------------------------------------------------------------------------Predicate Information (identified by operation id):--------------------------------------------------- PLAN_TABLE_OUTPUT--------------------------------------------------------------------------------   3 - access("EMPNO"=7902)   4 - filter(LNNVL("EMPNO"=7902))   5 - access("ENAME"='SMITH') 24 rows selected

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