1.绝对值：abs
select abs(-2) value from dual;
2.取整函数（大）：ceil
select ceil(-2.001) value from dual;(-2)
3.取整函数（小）：floor
select floor(-2.001) value from dual;(-3)
4.取整函数（截取）：trunc
select trunc(-2.001) value from dual; (-2)
5.四舍五入：round
select round(1.234564) value from dual;(1.2346)
6.取平方：Power
select power(4,2) value from dual;(16)
7.取平方根:SQRT
select sqrt(16) value from dual;(4)
8.取随机数:dbms_random(minvalue,maxvalue)
select sys.dbms.random.value(0,1) value from dual;
9.取符号：Sign
select sign(-3) value from dual;
当数值为负数，返回-1
当数值为0，返回0
当数值为正数，返回1
10,取集合的最大值:greatest
select greatest(-1,3,5,7,9) value from dual;(9)
11.取集合的最小值:least
select least(-1,3,5,7,9) value from dual;(-1)
12.处理Null值：nvl
select nvl(null,10) value from dual;(10)
13.求字符序号:ascii
select ascii(a) value from dual;
14.求序号字符:chr
select chr(97) value from dual;
15.链接：concat
select concat("11","22") value from dual;(1122)
16.获取系统时间:sysdate
select sysdate value from dual;
17.求日期
select trunc(sysdate) from dual;
18.求时间
select to_char(sysdate,"hh24:mm:ss") from dual;
19.首字母大写：InitCAP
select INITCAP(abc def ghi) value from dual;(Abc Def Ghi)
原文链接：https://blog.csdn.net/tianzengyan/article/details/5460661