SQL中的单记录函数
1.ASCII 返回与指定的字符对应的十进制数;
SQL> select ascii('A') A,ascii('a') a,ascii('0') zero,ascii(' ') space from dual;A A ZERO SPACE
--------- --------- --------- ---------65 97 48 32 2.CHR 给出整数,返回对应的字符;SQL> select chr(54740) zhao,chr(65) chr65 from dual;ZH C
-- -赵 A3.CONCAT 连接两个字符串;
SQL> select concat('010-','88888888')||'转23' 高乾竞电话 from dual;高乾竞电话
----------------010-88888888转234.INITCAP 返回字符串并将字符串的第一个字母变为大写;
SQL> select initcap('smith') upp from dual;UPP
-----Smith5.INSTR(C1,C2,I,J) 在一个字符串中搜索指定的字符,返回发现指定的字符的位置;
C1 被搜索的字符串C2 希望搜索的字符串I 搜索的开始位置,默认为1J 出现的位置,默认为1SQL> select instr('oracle traning','ra',1,2) instring from dual;INSTRING
---------96.LENGTH 返回字符串的长度;
SQL> select name,length(name),addr,length(addr),sal,length(to_char(sal)) from .nchar_tst;NAME LENGTH(NAME) ADDR LENGTH(ADDR) SAL LENGTH(TO_CHAR(SAL))
------ ------------ ---------------- ------------ --------- --------------------高乾竞 3 北京市海锭区 6 9999.99 77.LOWER 返回字符串,并将所有的字符小写
SQL> select lower('AaBbCcDd')AaBbCcDd from dual;AABBCCDD
--------aabbccdd8.UPPER 返回字符串,并将所有的字符大写
SQL> select upper('AaBbCcDd') upper from dual;UPPER
--------AABBCCDD9.RPAD和LPAD(粘贴字符)
RPAD 在列的右边粘贴字符LPAD 在列的左边粘贴字符SQL> select lpad(rpad('gao',10,'*'),17,'*')from dual;LPAD(RPAD('GAO',1
-----------------*******gao*******不够字符则用*来填满10.LTRIM和RTRIM
LTRIM 删除左边出现的字符串RTRIM 删除右边出现的字符串SQL> select ltrim(rtrim(' gao qian jing ',' '),' ') from dual;LTRIM(RTRIM('
-------------gao qian jing11.SUBSTR(string,start,count)
取子字符串,从start开始,取count个SQL> select substr('13088888888',3,8) from dual;SUBSTR('
--------0888888812.REPLACE('string','s1','s2')
string 希望被替换的字符或变量s1 被替换的字符串s2 要替换的字符串SQL> select replace('he love you','he','i') from dual;REPLACE('HELOVEYOU','HE','I')
------------------------------i love you13.SOUNDEX 返回一个与给定的字符串读音相同的字符串
SQL> create table table1(xm varchar(8));SQL> insert into table1 values('weather');SQL> insert into table1 values('wether');SQL> insert into table1 values('gao');SQL> select xm from table1 where soundex(xm)=soundex('weather');
XM
--------weatherwether14.TRIM('s' from 'string')
LEADING 剪掉前面的字符TRAILING 剪掉后面的字符如果不指定,默认为空格符15.ABS 返回指定值的绝对值
SQL> select abs(100),abs(-100) from dual;ABS(100) ABS(-100)
--------- ---------100 10016.ACOS 给出反余弦的值
SQL> select acos(-1) from dual;ACOS(-1)
---------3.141592717.ASIN 给出反正弦的值
SQL> select asin(0.5) from dual;ASIN(0.5)
---------.5235987818.ATAN 返回一个数字的反正切值
SQL> select atan(1) from dual;ATAN(1)
---------.7853981619.CEIL 返回大于或等于给出数字的最小整数
SQL> select ceil(3.1415927) from dual;CEIL(3.1415927)
---------------420.COS 返回一个给定数字的余弦
SQL> select cos(-3.1415927) from dual;COS(-3.1415927)
----------------121.COSH 返回一个数字反余弦值
SQL> select cosh(20) from dual;COSH(20)
---------24258259822.EXP 返回一个数字e的n次方根
SQL> select exp(2),exp(1) from dual;EXP(2) EXP(1)
--------- ---------7.3890561 2.718281823.FLOOR 对给定的数字取整数
SQL> select floor(2345.67) from dual;FLOOR(2345.67)
--------------234524.LN 返回一个数字的对数值
SQL> select ln(1),ln(2),ln(2.7182818) from dual;LN(1) LN(2) LN(2.7182818)
--------- --------- -------------0 .69314718 .9999999925.LOG(n1,n2) 返回一个以n1为底n2的对数
SQL> select log(2,1),log(2,4) from dual;LOG(2,1) LOG(2,4)
--------- ---------
26.MOD(n1,n2) 返回一个n1除以n2的余数
SQL> select mod(10,3),mod(3,3),mod(2,3) from dual;
MOD(10,3) MOD(3,3) MOD(2,3)
--------- --------- ---------1 0 227.POWER 返回n1的n2次方根
SQL> select power(2,10),power(3,3) from dual;POWER(2,10) POWER(3,3)
----------- ----------1024 2728.ROUND和TRUNC
按照指定的精度进行舍入SQL> select round(55.5),round(-55.4),trunc(55.5),trunc(-55.5) from dual;ROUND(55.5) ROUND(-55.4) TRUNC(55.5) TRUNC(-55.5)
----------- ------------ ----------- ------------56 -55 55 -5529.SIGN 取数字n的符号,大于0返回1,小于0返回-1,等于0返回0
SQL> select sign(123),sign(-100),sign(0) from dual;SIGN(123) SIGN(-100) SIGN(0)
--------- ---------- ---------1 -1 030.SIN 返回一个数字的正弦值
SQL> select sin(1.57079) from dual;SIN(1.57079)
------------131.SIGH 返回双曲正弦的值
SQL> select sin(20),sinh(20) from dual;
SIN(20) SINH(20)
--------- ---------.91294525 24258259832.SQRT 返回数字n的根
SQL> select sqrt(64),sqrt(10) from dual;SQRT(64) SQRT(10)
--------- ---------8 3.162277733.TAN 返回数字的正切值
SQL> select tan(20),tan(10) from dual;TAN(20) TAN(10)
--------- ---------2.2371609 .6483608334.TANH
返回数字n的双曲正切值SQL> select tanh(20),tan(20) from dual;TANH(20) TAN(20)
--------- ---------1 2.237160935.TRUNC
按照指定的精度截取一个数SQL> select trunc(124.1666,-2) trunc1,trunc(124.16666,2) from dual;TRUNC1 TRUNC(124.16666,2)
--------- ------------------100 124.1636.ADD_MONTHS
增加或减去月份SQL> select to_char(add_months(to_date('199912','yyyymm'),2),'yyyymm') from dual;TO_CHA
------200002SQL> select to_char(add_months(to_date('199912','yyyymm'),-2),'yyyymm') from dual;TO_CHA
------19991037.LAST_DAY
返回日期的最后一天SQL> select to_char(sysdate,'yyyy.mm.dd'),to_char((sysdate)+1,'yyyy.mm.dd') from dual;TO_CHAR(SY TO_CHAR((S
---------- ----------2004.05.09 2004.05.10SQL> select last_day(sysdate) from dual;LAST_DAY(S
----------31-5月 -0438.MONTHS_BETWEEN(date2,date1)
给出date2-date1的月份SQL> select months_between('19-12月-1999','19-3月-1999') mon_between from dual;MON_BETWEEN
-----------9SQL>selectmonths_between(to_date('2000.05.20','yyyy.mm.dd'),to_date('2005.05.20','yyyy.dd')) mon_betw from dual;MON_BETW
----------6039.NEW_TIME(date,'this','that')
给出在this时区=other时区的日期和时间SQL> select to_char(sysdate,'yyyy.mm.dd hh24:mi:ss') bj_time,to_char(new_time2 (sysdate,'PDT','GMT'),'yyyy.mm.dd hh24:mi:ss') los_angles from dual;BJ_TIME LOS_ANGLES
------------------- -------------------2004.05.09 11:05:32 2004.05.09 18:05:3240.NEXT_DAY(date,'day')
给出日期date和星期x之后计算下一个星期的日期SQL> select next_day('18-5月-2001','星期五') next_day from dual;NEXT_DAY
----------25-5月 -0141.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 11:17:0042.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 SMITHAAAAfKAACAAAAEqAAB AAAAfKAACAAAAEqAAB ALLENAAAAfKAACAAAAEqAAC AAAAfKAACAAAAEqAAC WARDAAAAfKAACAAAAEqAAD AAAAfKAACAAAAEqAAD JONES43.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
------strutz44.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 21:14:4148.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
---------199951.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# USERNAME CMD
--------- --------- ------------------------------ ------1 1 none2 1 none3 1 none4 1 none5 1 none6 1 none7 1275 none8 1275 none9 20 GAO select10 40 GAO none53.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 a30SQL> col dump_string for a50SQL> set lin 200SQL> 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,D54.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
--ACSQL> 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.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,VSIZEISDBA 查看当前用户是否是DBA如果是则返回trueSQL> select userenv('isdba') from dual;USEREN
------FALSESQL> select userenv('isdba') from dual;USEREN
------TRUESESSION返回会话标志SQL> select userenv('sessionid') from dual;USERENV('SESSIONID')
--------------------152ENTRYID返回会话人口标志SQL> select userenv('entryid') from dual;USERENV('ENTRYID')
------------------0INSTANCE返回当前INSTANCE的标志SQL> select userenv('instance') from dual;USERENV('INSTANCE')
-------------------1LANGUAGE返回当前环境变量SQL> select userenv('language') from dual;USERENV('LANGUAGE')
----------------------------------------------------SIMPLIFIED CHINESE_CHINA.ZHS16GBKLANG返回当前环境的语言的缩写SQL> select userenv('lang') from dual;USERENV('LANG')
----------------------------------------------------ZHSTERMINAL返回用户的终端或机器的标志SQL> select userenv('terminal') from dual;USERENV('TERMINA
----------------GAOVSIZE(X)返回X的大小(字节)数SQL> select vsize(user),user from dual;VSIZE(USER) USER
----------- ------------------------------6 SYSTEM
58 COALESCE
COALESCE (expression_1, expression_2, ...,expression_n)依次参考各参数表达式，遇到非null值即停止并返回该值。如果所有的表达式都是空值，最终将返回一个空值。
使用COALESCE在于大部分包含空值的表达式最终将返回空值。
eg:
SELECT COALESCE(NULL,NULL,3,4,5) FROM dual result: 3