[20130803]ORACLE 12C TOP N SQL实现分页功能.txt

[20130803]ORACLE 12C TOP N SQL实现分页功能.txt

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SQL> @ver
BANNER                                                                               CON_ID
-------------------------------------------------------------------------------- ----------
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production              0

select * fro emp;

SQL> SELECT * FROM emp ORDER BY empno ;

     EMPNO ENAME      JOB              MGR HIREDATE                   SAL       COMM     DEPTNO

---------- ---------- --------- ---------- ------------------- ---------- ---------- ----------

      7369 SMITH      CLERK           7902 1980-12-17 00:00:00        800                    20

      7499 ALLEN      SALESMAN        7698 1981-02-20 00:00:00       1600        300         30

      7521 WARD       SALESMAN        7698 1981-02-22 00:00:00       1250        500         30

      7566 JONES      MANAGER         7839 1981-04-02 00:00:00       2975                    20

      7654 MARTIN     SALESMAN        7698 1981-09-28 00:00:00       1250       1400         30

      7698 BLAKE      MANAGER         7839 1981-05-01 00:00:00       2850                    30

      7782 CLARK      MANAGER         7839 1981-06-09 00:00:00       2450                    10

      7788 SCOTT      ANALYST         7566 1987-04-19 00:00:00       3000                    20

      7839 KING       PRESIDENT            1981-11-17 00:00:00       5000                    10

      7844 TURNER     SALESMAN        7698 1981-09-08 00:00:00       1500          0         30

      7876 ADAMS      CLERK           7788 1987-05-23 00:00:00       1100                    20

      7900 JAMES      CLERK           7698 1981-12-03 00:00:00        950                    30

      7902 FORD       ANALYST         7566 1981-12-03 00:00:00       3000                    20

      7934 MILLER     CLERK           7782 1982-01-23 00:00:00       1300                    10

14 rows selected.

SQL> SELECT * FROM emp ORDER BY empno offset 5 rows FETCH next 5 ROWS ONLY;

     EMPNO ENAME      JOB              MGR HIREDATE                   SAL       COMM     DEPTNO

---------- ---------- --------- ---------- ------------------- ---------- ---------- ----------

      7698 BLAKE      MANAGER         7839 1981-05-01 00:00:00       2850                    30

      7782 CLARK      MANAGER         7839 1981-06-09 00:00:00       2450                    10

      7788 SCOTT      ANALYST         7566 1987-04-19 00:00:00       3000                    20

      7839 KING       PRESIDENT            1981-11-17 00:00:00       5000                    10

      7844 TURNER     SALESMAN        7698 1981-09-08 00:00:00       1500          0         30

--注意一个细节，这种方式sqlplus没有14 rows selected.相似的提示信息。除非next N能全部取完。

--查看执行计划:

SQL> @dpc '' ''

PLAN_TABLE_OUTPUT

------------------------------------------------------------------------

SQL_ID  dnncqfs9xrpc7, child number 0

-------------------------------------

SELECT * FROM emp ORDER BY empno offset 5 rows FETCH next 5 ROWS ONLY

Plan hash value: 2801941731

----------------------------------------------------------------------

| Id  | Operation                     | Name   | E-Rows | Cost (%CPU)|

----------------------------------------------------------------------

|   0 | SELECT STATEMENT              |        |        |     2 (100)|

|*  1 |  VIEW                         |        |     14 |     2   (0)|

|*  2 |   WINDOW NOSORT STOPKEY       |        |     14 |     2   (0)|

|   3 |    TABLE ACCESS BY INDEX ROWID| EMP    |     14 |     2   (0)|

|   4 |     INDEX FULL SCAN           | PK_EMP |     14 |     1   (0)|

----------------------------------------------------------------------

Predicate Information (identified by operation id):

---------------------------------------------------

   1 - filter(("from$_subquery$_002"."rowlimit_$$_rownumber"

              WHEN (5>=0) THEN 5 ELSE 0 END +5 AND

              "from$_subquery$_002"."rowlimit_$$_rownumber">5))

   2 - filter(ROW_NUMBER() OVER ( ORDER BY "EMP"."EMPNO")

              (5>=0) THEN 5 ELSE 0 END +5)

--实际上本质还是使用分析函数ROW_NUMBER()。只不过这样写简单一些。