[20130803]ORACLE 12C TOP N SQL实现分页功能.txt
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SQL> @ver
BANNER CON_ID
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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。
时间： 2024-10-23 20:10:09