技巧:ORACLE应用常见傻瓜问题1000问(四)
133. CURRVAL 和 nextval
为表创建序列
CREATE SEQUENCE EMPSEQ ... ;
SELECT empseq.currval FROM DUAL ;
自动插入序列的数值
INSERT INTO emp
VALUES (empseq.nextval, 'LEWIS', 'CLERK', 7902, SYSDATE, 1200, NULL, 20) ;
134. ROWNUM
按设定排序的行的序号
SELECT * FROM emp WHERE ROWNUM < 10 ;
135. ROWID
返回行的物理地址
SELECT ROWID, ename FROM emp WHERE deptno = 20 ;
136. 将N秒转换为时分秒格式?
set serverout on
declare
N number := 1000000;
ret varchar2(100);
begin
ret := trunc(n/3600) || '小时' || to_char(to_date(mod(n,3600),'sssss'),'fmmi"分 "ss"秒"') ;
dbms_output.put_line(ret);
end;
137. 如何查询做比较大的排序的进程?
SELECT b.tablespace, b.segfile#, b.segblk#, b.blocks, a.sid, a.serial#,
a.username, a.osuser, a.status
FROM v$session a,v$sort_usage b
WHERE a.saddr = b.session_addr
ORDER BY b.tablespace, b.segfile#, b.segblk#, b.blocks ;
138. 如何查询做比较大的排序的进程的SQL语句?
select /*+ ORDERED */ sql_text from v$sqltext a
where a.hash_value = (
select sql_hash_value from v$session b
where b.sid = &sid and b.serial# = &serial)
order by piece asc ;
139. 如何查找重复记录?
SELECT * FROM TABLE_NAME
WHERE ROWID!=(SELECT MAX(ROWID) FROM TABLE_NAME D
WHERE TABLE_NAME.COL1=D.COL1 AND TABLE_NAME.COL2=D.COL2);
140. 如何删除重复记录?
DELETE FROM TABLE_NAME
WHERE ROWID!=(SELECT MAX(ROWID) FROM TABLE_NAME D
WHERE TABLE_NAME.COL1=D.COL1 AND TABLE_NAME.COL2=D.COL2);
141. 如何快速编译所有视图?
SQL >SPOOL VIEW1.SQL
SQL >SELECT ‘ALTER VIEW ‘||TNAME||’
COMPILE;’ FROM TAB;
SQL >SPOOL OFF
然后执行VIEW1.SQL即可。
SQL >@VIEW1.SQL;
142. ORA-01555 SNAPSHOT TOO OLD的解决办法
增加MINEXTENTS的值,增加区的大小,设置一个高的OPTIMAL值。
143. 事务要求的回滚段空间不够,表现为表空间用满(ORA-01560错误),回滚段扩展到达参数MAXEXTENTS的值(ORA-01628)的解决办法.
向回滚段表空间添加文件或使已有的文件变大;增加MAXEXTENTS的值。
144. 如何加密ORACLE的存储过程?
下列存储过程内容放在AA.SQL文件中
create or replace procedure testCCB(i in number) as
begin
dbms_output.put_line('输入参数是'||to_char(i));
end;
SQL>wrap iname=a.sql;
PL/SQL Wrapper: Release 8.1.7.0.0 - Production on Tue Nov 27 22:26:48 2001
Copyright (c) Oracle Corporation 1993, 2000. All Rights Reserved.
Processing AA.sql to AA.plb
运行AA.plb
SQL> @AA.plb ;
145. 如何监控事例的等待?
select event,sum(decode(wait_Time,0,0,1)) "Prev",
sum(decode(wait_Time,0,1,0)) "Curr",count(*) "Tot"
from v$session_Wait
group by event order by 4;