总结归纳：110个Oracle常用函数的总结(6)

文章作者 100test 发表时间 2007:07:02 12:16:05
来源 100Test.Com百考试题网

51.BFILENAME(dir,file)
指定一个外部二进制文件
SQL>insert into file_tb1 values(bfilename(lob_dir1,image1.gif)).

52.CONVERT(x,desc,source)
将x字段或变量的源source转换为desc
SQL> 0select sid,serial#,username,decode(command,
2 0,none,
3 2,insert,
4 3,
5 0select,
6 6,0update,
7 7,0delete,
8 8,0drop,
9 other) cmd from v$session where type!=background.

SID SERIAL# USERNAME CMD
--------- --------- ------------------------------ ------
1 1 none
2 1 none
3 1 none
4 1 none
5 1 none
6 1 none
7 1275 none
8 1275 none
9 20 GAO 0select
10 40 GAO none

53.DUMP(s,fmt,start,length)
DUMP函数以fmt指定的内部数字格式返回一个VARCHAR2类型的值
SQL> col global_name for a30
SQL> col dump_string for a50
SQL> set lin 200
SQL> 0select global_name,dump(global_name,1017,8,5) dump_string from global_name.

GLOBAL_NAME DUMP_STRING
------------------------------ --------------------------------------------------
ORACLE.WORLD Typ=1 Len=12 CharacterSet=ZHS16GBK: W,O,R,L,D

54.EMPTY_BLOB()和EMPTY_CLOB()
这两个函数都是用来对大数据类型字段进行初始化操作的函数

55.GREATEST
返回一组表达式中的最大值,即比较字符的编码大小.
SQL> 0select greatest(AA,AB,AC) from dual.

GR
--
AC
SQL> 0select greatest(啊,安,天) from dual.

GR
--
天

56.LEAST
返回一组表达式中的最小值
SQL> 0select least(啊,安,天) from dual.

LE
--
啊

57.UID
返回标识当前用户的唯一整数
SQL> show user
USER 为"GAO"
SQL> 0select username,user_id from dba_users where user_id=uid.

USERNAME USER_ID
------------------------------ ---------
GAO 25

58.USER
返回当前用户的名字
SQL> 0select user from dual.

USER
------------------------------
GAO

59.USEREVN
返回当前用户环境的信息,opt可以是:
ENTRYID,SESSIONID,TERMINAL,ISDBA,LABLE,LANGUAGE,CLIENT_INFO,LANG,VSIZE
ISDBA 查看当前用户是否是DBA如果是则返回true
SQL> 0select userenv(isdba) from dual.

USEREN
------
FALSE
SQL> 0select userenv(isdba) from dual.

USEREN
------
TRUE
SESSION
返回会话标志
SQL> 0select userenv(sessionid) from dual.

USERENV(SESSIONID)
--------------------
152
ENTRYID
返回会话人口标志
SQL> 0select userenv(entryid) from dual.

USERENV(ENTRYID)
------------------
0
INSTANCE
返回当前INSTANCE的标志
SQL> 0select userenv(instance) from dual.

USERENV(INSTANCE)
-------------------
1
LANGUAGE
返回当前环境变量
SQL> 0select userenv(language) from dual.

USERENV(LANGUAGE)
----------------------------------------------------
SIMPLIFIED CHINESE_CHINA.ZHS16GBK
LANG
返回当前环境的语言的缩写
SQL> 0select userenv(lang) from dual.

USERENV(LANG)
----------------------------------------------------
ZHS
TERMINAL
返回用户的终端或机器的标志
SQL> 0select userenv(terminal) from dual.

USERENV(TERMINA
----------------
GAO
VSIZE(X)
返回X的大小(字节)数
SQL> 0select vsize(user),user from dual.

VSIZE(USER) USER
----------- ------------------------------
6 SYSTEM

60.AVG(DISTINCT|ALL)
all表示对所有的值求平均值,distinct只对不同的值求平均值
SQLWKS> create table table3(xm varchar(8),sal number(7,2)).
语句已处理。
SQLWKS> insert into table3 values(gao,1111.11).
SQLWKS> insert into table3 values(gao,1111.11).
SQLWKS> insert into table3 values(zhu,5555.55).
SQLWKS> commit.

SQL> 0select avg(distinct sal) from gao.table3.

AVG(DISTINCTSAL)
----------------
3333.33

SQL> 0select avg(all sal) from gao.table3.

AVG(ALLSAL)
-----------
2592.59

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