Question

我试图了解索引提示，但即使在查询中提供提示后它也没有被使用过。这是我遵循的步骤，我错过了什么？

SQL> desc emp_1;
Name     Type         Nullable Default Comments 
-------- ------------ -------- ------- -------- 
EMP_ID   NUMBER                                 
EMP_NAME VARCHAR2(20) Y                         
DEPTNO   NUMBER(10)   Y               


SQL> desc dept
Name      Type         Nullable Default Comments 
--------- ------------ -------- ------- -------- 
DEPT_ID   NUMBER       Y                         
DEPT_NAME VARCHAR2(20) Y                         


SQL> CREATE INDEX abc_idex ON emp_1 (deptno);

Index created

select  /*+ index(emp_1.abc_idex) */ emp_name from emp_1
INNER JOIN dept ON  emp_1.deptno = dept.dept_id

解释计划： -

SELECT STATEMENT, GOAL = ALL_ROWS           6   1   28
 HASH JOIN          6   1   28
  TABLE ACCESS FULL EXAMINBI    EMP_1   2   1   25
  TABLE ACCESS FULL EXAMINBI    DEPT    3   4   12

根据Rene的回答

select  /*+ index(emp_1 abc_idex) */ emp_name from emp_1
INNER JOIN dept ON  emp_1.deptno = dept.dept_id

解释计划

SELECT STATEMENT, GOAL = ALL_ROWS           271 100000  800000
 MERGE JOIN         271 100000  800000
  TABLE ACCESS BY INDEX ROWID   EXAMINBI    EMP_1   267 100000  500000
   INDEX FULL SCAN  EXAMINBI    ABC_IDEX    131 100000  
  SORT JOIN         4   4   12
   TABLE ACCESS FULL    EXAMINBI    DEPT    3   4   12

Answer 1

根据Tahitis documentation，您不得在表格规范和索引规范之间添加.。

索引提示无效

1 个答案: