Oracle分页查询
2014-04-26 17:03
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RowNum:表示行号,实际上是一个列,这个列是伪列。
例子:
SELECT ROWNUM,empno,ename,job,sal,hiredate FROM emp;
SELECT ROWNUM,empno,ename,job,sal,hiredate FROM emp WHERE RowNum<=5;
SELECT ROWNUM,empno,ename,job,sal,hiredate FROM emp WHERE RowNum BETWEEN 5 AND 10;(显示不出来)
如果想要进行中间的截取操作,则只能采用子查询,例如现在假设每页显示5条记录,第二页应该显示6-10条。那么对于数据库操作来讲,它在查询的时候应该首先查询出1-10条,之后再在查询的结果中取出。
SELECT * FROM(SELECT ROWNUM rn,empno,ename,job,sal,hiredate FROM emp WHERE RowNum<=10) temp WHERE temp.rn>5;
--每页5条
--查询第二页
SELECT *
FROM (SELECT ROWNUM RN, EMPNO, ENAME, JOB, SAL, HIREDATE
FROM EMP
WHERE ROWNUM <= 2*5) TEMP
WHERE TEMP.RN > (2-1)*5;
等于
SELECT *
FROM (SELECT ROWNUM RN, T1.*
FROM (SELECT * FROM EMP) T1
WHERE ROWNUM <= 2 * 5)
WHERE RN > (2 - 1) * 5;
分页查询模板
SELECT * FROM (SELECT ROWNUM RN, a1.* FROM ( SELECT EMPNO, ENAME, JOB, SAL, HIREDATE
FROM EMP ORDER BY EMPNO) a1
WHERE ROWNUM <= 2*5) TEMP
WHERE TEMP.RN > (2-1)*5;
根据Rowid分页效率最快
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 <= 3*5)
WHERE rn>(3-1)*5)ORDER BY EMPNO DESC;
例子:
SELECT ROWNUM,empno,ename,job,sal,hiredate FROM emp;
SELECT ROWNUM,empno,ename,job,sal,hiredate FROM emp WHERE RowNum<=5;
SELECT ROWNUM,empno,ename,job,sal,hiredate FROM emp WHERE RowNum BETWEEN 5 AND 10;(显示不出来)
如果想要进行中间的截取操作,则只能采用子查询,例如现在假设每页显示5条记录,第二页应该显示6-10条。那么对于数据库操作来讲,它在查询的时候应该首先查询出1-10条,之后再在查询的结果中取出。
SELECT * FROM(SELECT ROWNUM rn,empno,ename,job,sal,hiredate FROM emp WHERE RowNum<=10) temp WHERE temp.rn>5;
--每页5条
--查询第二页
SELECT *
FROM (SELECT ROWNUM RN, EMPNO, ENAME, JOB, SAL, HIREDATE
FROM EMP
WHERE ROWNUM <= 2*5) TEMP
WHERE TEMP.RN > (2-1)*5;
等于
SELECT *
FROM (SELECT ROWNUM RN, T1.*
FROM (SELECT * FROM EMP) T1
WHERE ROWNUM <= 2 * 5)
WHERE RN > (2 - 1) * 5;
分页查询模板
SELECT * FROM (SELECT ROWNUM RN, a1.* FROM ( SELECT EMPNO, ENAME, JOB, SAL, HIREDATE
FROM EMP ORDER BY EMPNO) a1
WHERE ROWNUM <= 2*5) TEMP
WHERE TEMP.RN > (2-1)*5;
根据Rowid分页效率最快
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 <= 3*5)
WHERE rn>(3-1)*5)ORDER BY EMPNO DESC;
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