人背信则名不达的意思:oracle常用函数汇集

1.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

2.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                    7

3.LOWER
返回字符串,并将所有的字符小写
SQL> select lower('AaBbCcDd')AaBbCcDd from dual;

AABBCCDD
--------
aabbccdd

4.UPPER
返回字符串,并将所有的字符大写
SQL> select upper('AaBbCcDd') upper from dual;

UPPER
--------
AABBCCDD

5.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

6.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

7.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

8.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 you

9.ABS
返回指定值的绝对值
SQL> select abs(100),abs(-100) from dual;

ABS(100) ABS(-100)
--------- ---------
100       100

10.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

11.FLOOR
对给定的数字取整数
SQL> select floor(2345.67) from dual;

FLOOR(2345.67)
--------------
  2345

12.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

13.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

14.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

15.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.dd')) mon_betw from dual;

MON_BETW
---------
-60

16.SYSDATE
用来得到系统的当前日期
SQL> select to_char(sysdate,'dd-mm-yyyy day') from dual;

17.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

18.TO_DATE(string,'format')
将字符串转化为ORACLE中的一个日期

19.TO_NUMBER
将给出的字符转换为数字
SQL> select to_number('1999') year from dual;

     YEAR
---------
     1999

20.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

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

LE
--
啊

22.USER
返回当前用户的名字
SQL> select user from  du

 23.round:舍入

round();

24.dual  伪表
 select 1 from dual

25.decode
decode(substrb(month,5,2),'01',sell,0)

26.nvl 返回非空