目录
行号:ROWNUM
对数据进行动态添加序号
SELECT ROWNUM,ename,sal FROM emp;
作用:
- 获取第一条数据;
SELECT * FROM emp WHERE ROWNUM=1;
-
获取前N条数据
SELECT * FROM emp WHERE ROWNUM<=6;
数据分页:
例:取出6~10行数据
SELECT *
FROM (SELECT empno,ename,job,sal,hiredate,ROWNUM rn FROM emp WHERE ROWNUM<=10) temp
WHERE temp.rn>5;
行ID:ROWID
物理地址编号
SELECT ROWID,ename FROM emp;
ROWID
-----------------------------------
AAAR3sAAEAAAACXAAA
AAAR3sAAEAAAACXAAB
AAAR3sAAEAAAACXAAC
AAAR3sAAEAAAACXAAD
- 数据的的对象编号:AAAR3s
- 数据保存的文件编号:AAE
- 数据保存的块号:AAAACX
- 数据的保存行号:AAA
删除重复操作
DELETE FROM mydept
WHERE ROWID NOT IN(SELECT MIN(ROWID)
FROM mydept
GROUP BY deptno,dname,loc);