oracle的分页一共有三种方式
方法一 根据rowid来分
SELECT * FROM EMP WHERE ROWID IN (SELECT RID FROM (SELECT ROWNUM RN, RID FROM (SELECT ROWID RID, EMPNO FROM EMP ORDER BY EMPNO DESC) WHERE ROWNUM <= ( (currentPage-1) * pageSize + pageSize )) --每页显示几条 WHERE RN > ((currentPage-1) * pageSize) ) --当前页数 ORDER BY EMPNO DESC; eg、 -- 5 = (currentPage-1) * pageSize + pageSize 每页显示几条 -- 0 = (currentPage-1) * pageSize 当前页数 SELECT * FROM EMP WHERE ROWID IN (SELECT RID FROM (SELECT ROWNUM RN, RID FROM (SELECT ROWID RID, EMPNO FROM EMP ORDER BY EMPNO DESC) WHERE ROWNUM <= ( (1-1) * 5 + 5 )) --每页显示几条 WHERE RN > ((1-1) * 5) ) --当前页数 ORDER BY EMPNO DESC
方法二 按分析函数来分
SELECT * FROM (SELECT T.*, ROW_NUMBER() OVER(ORDER BY empno DESC) RK FROM emp T) WHERE RK <= ( (currentPage-1) * pageSize + pageSize ) --每页显示几条 AND RK > ( (currentPage-1) * pageSize ); --当前页数 eg、 -- 5 = (currentPage-1) * pageSize + pageSize 每页显示几条 -- 0 = (currentPage-1) * pageSize 当前页数 SELECT * FROM (SELECT T.*, ROW_NUMBER() OVER(ORDER BY empno DESC) RK FROM emp T) WHERE RK <= 5 AND RK > 0;
方法三 按rownum 来分
SELECT * FROM (SELECT T.*, ROWNUM RN FROM (SELECT * FROM EMP ORDER BY EMPNO DESC) T WHERE ROWNUM <= ( (currentPage-1) * pageSize + pageSize )) --每页显示几条 WHERE RN > ( (currentPage-1) * pageSize ); --当前页数 eg、 -- 5 = (currentPage-1) * pageSize + pageSize 每页显示几条 -- 0 = (currentPage-1) * pageSize 当前页数 SELECT * FROM (SELECT T.*, ROWNUM RN FROM (SELECT * FROM EMP ORDER BY EMPNO DESC) T WHERE ROWNUM <= 5) WHERE RN > 0;
其中emp为表名称，empno 为表的主键id，获取按empno降序排序后的第1-5条记录，emp表有70000 多条记录。
个人感觉方法一的效率最好，方法三 次之，方法二 最差。
下面通过方法三来分析oracle怎么通过rownum分页的
1、 SELECT * FROM emp; 2、显示rownum，由oracle分配的 SELECT e.*, ROWNUM rn FROM (SELECT * FROM emp) e; --rn相当于Oracle分配的行的ID号 3、先查出1-10条记录 正确的: SELECT e.*, ROWNUM rn FROM (SELECT * FROM emp) e WHERE ROWNUM<=10; 错误的：SELECT e.*, ROWNUM rn FROM (SELECT * FROM emp) e WHERE rn<=10; 4、然后查出6-10条记录 SELECT * FROM (SELECT e.*, ROWNUM rn FROM (SELECT * FROM emp) e WHERE ROWNUM<=10) WHERE rn>=6;