索引扫描(四)-索引全扫描-优快云博客

本文展示了如何使用SQL查询员工表中的索引信息，并提供了一个具体的例子来说明如何获取特定索引的详细情况，包括索引名称、列名及列位置等。

SQL> select table_name,index_name,column_name,column_position from user_Ind_columns where table_name='EMPLOYEES';

TABLE_NAME           INDEX_NAME                     COLUMN_NAME     COLUMN_POSITION
-------------------- ------------------------------ --------------- ---------------
EMPLOYEES            EMP_EMAIL_UK                   EMAIL                         1
EMPLOYEES            EMP_EMP_ID_PK                  EMPLOYEE_ID                   1
EMPLOYEES            EMP_DEPARTMENT_IX              DEPARTMENT_ID                 1
EMPLOYEES            EMP_JOB_IX                     JOB_ID                        1
EMPLOYEES            EMP_MANAGER_IX                 MANAGER_ID                    1
EMPLOYEES            EMP_NAME_IX                    LAST_NAME                     1
EMPLOYEES            EMP_NAME_IX                    FIRST_NAME                    2

SQL> set autot traceonly explain
SQL> select last_name,first_name from employees;

Execution Plan
----------------------------------------------------------
Plan hash value: 2228653197

--------------------------------------------------------------------------------
| Id | Operation        | Name        | Rows | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------
|   0 | SELECT STATEMENT |             |   107 | 1605 |     1   (0)| 00:00:01 |
|   1 | INDEX FULL SCAN | EMP_NAME_IX |   107 | 1605 |     1   (0)| 00:00:01 |
--------------------------------------------------------------------------------

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