时间：2021-07-01 10:21:17 帮助过：50人阅读
.SYSDATE
用来得到系统的当前日期
SQL> select to_char(sysdate,dd-mm-yyyy day) from dual;
TO_CHAR(SYSDATE,
-----------------
09-05-2004星期日
trunc(date,fmt)按照给出的要求将日期截断,如果fmt=mi表示保留分,截断秒SQL> select to_char(trunc(sysdate,hh),yyyy.mm.dd hh24:mi:ss) hh, 2 to_char(trunc(sysdate,mi),yyyy.mm.dd hh24:mi:ss) hhmm from dual;
HH HHMM
------------------- -------------------
2004.05.09 11:00:00 2004.05.09 11:17:00
42.CHARTOROWID
将字符数据类型转换为ROWID类型
SQL> select rowid,rowidtochar(rowid),ename from scott.emp;
ROWID ROWIDTOCHAR(ROWID) ENAME
------------------ ------------------ ----------
AAAAfKAACAAAAEqAAA AAAAfKAACAAAAEqAAA SMITH
AAAAfKAACAAAAEqAAB AAAAfKAACAAAAEqAAB ALLEN
AAAAfKAACAAAAEqAAC AAAAfKAACAAAAEqAAC WARD
AAAAfKAACAAAAEqAAD AAAAfKAACAAAAEqAAD JONES
43.CONVERT(c,dset,sset)
将源字符串sset从一个语言字符集转换到另一个目的dset字符集
SQL> select convert(strutz,we8hp,f7dec) "conversion" from dual;
conver
------
strutz
44.HEXTORAW
将一个十六进制构成的字符串转换为二进制
45.RAWTOHEXT
将一个二进制构成的字符串转换为十六进制
46.ROWIDTOCHAR
将ROWID数据类型转换为字符类型
47.TO_CHAR(date,format) SQL> select to_char(sysdate,yyyy/mm/dd hh24:mi:ss) from dual;
TO_CHAR(SYSDATE,YY
-------------------
2004/05/09 21:14:41
48.TO_DATE(string,format)
将字符串转化为ORACLE中的一个日期
49.TO_MULTI_BYTE
将字符串中的单字节字符转化为多字节字符
SQL> select to_multi_byte(高) from dual;
TO
--
高
50.TO_NUMBER
将给出的字符转换为数字
SQL> select to_number(1999) year from dual;
YEAR
---------
1999
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> select sid,serial#,username,decode(command, 2 0,none, 3 2,insert, 4 3, 5 select, 6 6,update, 7 7,delete, 8 8,drop, 9 other) cmd from v$session where type!=background;
SID SERIAL# USERNAM
E 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 select
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> select 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> select greatest(AA,AB,AC) from dual;
GR
--
AC
SQL> select greatest(啊,安,天) from dual;
GR
--
天
56.LEAST
返回一组表达式中的最小值
SQL> select 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> select 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> select 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> select userenv(isdba) from dual;
USEREN
------
FALSE
SQL> select userenv(isdba) from dual;
USEREN
------
TRUE
SESSION
返回会话标志
SQL> select userenv(sessionid) from dual;
USERENV(SESSIONID)
--------------------
152
ENTRYID
返回会话人口标志
SQL> select userenv(entryid) from dual;
USERENV(ENTRYID)
------------------
0
INSTANCE
返回当前INSTANCE的标志
SQL> select userenv(instance) from dual;
USERENV(INSTANCE)
-------------------
1
LANGUAGE
返回当前环境变量
SQL> select userenv(language) from dual;
USERENV(LANGUAGE)
----------------------------------------------------
SIMPLIFIED CHINESE_CHINA.ZHS16GBK
LANG
返回当前环境的语言的缩写
SQL> select userenv(lang) from dual;
USERENV(LANG)
----------------------------------------------------
ZHS
TERMINAL
返回用户的终端或机器的标志
SQL> select userenv(terminal) from dual;
USERENV(TERMINA
----------------
GAO
VSIZE(X)
返回X的大小(字节)数
SQL> select 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> select avg(distinct sal) from gao.table3;
AVG(DISTINCTSAL)
----------------
3333.33 SQL> select avg(all sal) from gao.table3;
AVG(ALLSAL)
-----------
2592.59