Oracle系列之

SQL中的函数

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;

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 A

3.CONCAT

连接两个字符串;

SQL> select concat('010-','88888888')||'转23'  高竞电话 from dual;
高竞电话 ---------------- 010-88888888转23

4.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 ----- Smith

5.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1
• J 出现的位置,默认为1

SQL> select instr('oracle traning','ra',1,2) instring from dual;
 INSTRING ---------         9

6.LENGTH

返回字符串的长度;

SQL> select name,length(name),addr,length(addr),sal,length(to_char(sal)) from gao.nchar_tst;
NAME   LENGTH(NAME) ADDR             LENGTH(ADDR)       SAL LENGTH(TO_CHAR(SAL)) 
------------------------------------------------ ------------ ---------------- --
高竞            3 西安市高新区                6   9999.99                    7

7.LOWER

返回字符串,并将所有的字符小写

SQL> select lower('AaBbCcDd')AaBbCcDd from dual;
AABBCCDD -------- aabbccdd

8.UPPER

返回字符串,并将所有的字符大写

SQL> select upper('AaBbCcDd') upper from dual;
UPPER -------- AABBCCDD

9.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 jing

11.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(' -------- 08888888

12.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('H ---------- i love you

13.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 -------- weather wether

14.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       100

16.ACOS

给出反余弦的值

SQL> select acos(-1) from dual;
ACOS(-1) --------- 3.1415927

17.ASIN

给出反正弦的值

SQL> select asin(0.5) from dual;
ASIN(0.5) --------- .52359878

18.ATAN

返回一个数字的反正切值

SQL> select atan(1) from dual;
ATAN(1) --------- .78539816

19.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) ---------------               4

20.COS

返回一个给定数字的余弦

SQL> select cos(-3.1415927) from dual;
COS(-3.1415927) ---------------              -1

21.COSH

返回一个数字反余弦值

SQL> select cosh(20) from dual;
COSH(20) --------- 242582598

22.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 2.7182818

23.FLOOR

对给定的数字取整数

SQL> select floor(2345.67) from dual;
FLOOR(2345.67) --------------           2345

24.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     .99999999

25.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) --------- ---------         0         2

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         2

27.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         27

28.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          -55

29.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         0

30.SIN

返回一个数字的正弦值

SQL> select sin(1.57079) from dual;
SIN(1.57079) ------------            1

31.SIGH

返回双曲正弦的值

SQL> select sin(20),sinh(20) from dual;
SIN(20)  SINH(20) --------- --------- .91294525 242582598

32.SQRT

返回数字n的根

SQL> select sqrt(64),sqrt(10) from dual;
SQRT(64)  SQRT(10) --------- ---------         8 3.1622777

33.TAN

返回数字的正切值

SQL> select tan(20),tan(10) from dual;
TAN(20)   TAN(10) --------- --------- 2.2371609 .64836083

34.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 2.2371609

35.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             124.16

36.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 ------ 200002 SQL> select to_char(add_months(to_date('199912','yyyymm'),-2),'yyyymm') from dual;
TO_CHA ------ 199910

37.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 2004.05.10 SQL> select last_day(sysdate) from dual;
LAST_DAY(S ---------- 31-5月 -04

38.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 -----------           9
SQL>selectmonths_between(to_date('2000.05.20','yyyy.mm.dd'),to_date('2005.05.20','yyyy.mm.dd')) mon_betw from dual;
MON_BETW ---------       -60

39.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_time   2  (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 18:05:32

40.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 -01

41.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# 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                            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

61.MAX(DISTINCT|ALL)

求最大值,

• ALL表示对所有的值求最大值,
• DISTINCT表示对不同的值求最大值,相同的只取一次

SQL> select max(distinct sal) from scott.emp;
MAX(DISTINCTSAL) ----------------             5000

62.MIN(DISTINCT|ALL)

求最小值,ALL表示对所有的值求最小值,DISTINCT表示对不同的值求最小值,相同的只取一次

SQL> select min(all sal) from gao.table3;
MIN(ALLSAL) -----------     1111.11

63.STDDEV(distinct|all)

求标准差,

• ALL表示对所有的值求标准差,
• DISTINCT表示只对不同的值求标准差

SQL> select stddev(sal) from scott.emp;
STDDEV(SAL) -----------   1182.5032
SQL> select stddev(distinct sal) from scott.emp;
STDDEV(DISTINCTSAL) -------------------            1229.951

64.VARIANCE(DISTINCT|ALL)

求协方差

SQL> select variance(sal) from scott.emp;
VARIANCE(SAL) -------------     1398313.9

65.GROUP BY

主要用来对一组数进行统计

SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno;
   DEPTNO  COUNT(*)  SUM(SAL) --------- --------- ---------       
10         3      8750        20         5     10875        30         6      9400

66.HAVING

对分组统计再加限制条件

SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno having count(*)>=5;
   DEPTNO  COUNT(*)  SUM(SAL) --------- --------- ---------       
20         5     10875        30         6      9400
SQL> select deptno,count(*),sum(sal) from scott.emp having count(*)>=5 group by deptno ;
   DEPTNO  COUNT(*)  SUM(SAL) --------- --------- ---------       
20         5     10875        30         6      9400

67.ORDER BY

用于对查询到的结果进行排序输出

SQL> select deptno,ename,sal from scott.emp order by deptno,sal desc;
   DEPTNO ENAME            SAL --------- ---------- ---------       
10 KING            5000       
10 CLARK           2450       
10 MILLER          1300       
20 SCOTT           3000       
20 FORD            3000       
20 JONES           2975       
20 ADAMS           1100      
20 SMITH            800      
30 BLAKE           2850       
30 ALLEN           1600       
30 TURNER          1500       
30 WARD            1250       
30 MARTIN          1250       
30 JAMES            950