oracle之常用简单函数（ONE)(二)
l]
SQL> select power(2,3) from dual;
POWER(2,3)
----------
8
SQL>
6）sqrt(x)：该函数用户求x的平方根，x必须大于等于0
eg：
[sql]
SQL> select sqrt(4) from dual;
SQRT(4)
----------
2
SQL>
7）round（x，【y】）：求x的取整结果，如果指定y，那么说明在小数点的y处开始取整，如果y为负值，那么要在x的小数点向左y处取整。
eg：
[sql]
SQL> select round(22.333,2) from dual;
ROUND(22.333,2)
---------------
22.33
SQL> select round(22.333,-2) from dual;
ROUND(22.333,-2)
----------------
0
SQL> select round (222.333,-2) from dual;
ROUND(222.333,-2)
-----------------
200
SQL> select round(22.263,2) from dual;
ROUND(22.263,2)
---------------
22.26
SQL> select round(22.263,1) from dual;
ROUND(22.263,1)
---------------
22.3
SQL>
8）sign(x)：该函数用于检测数值的正负，如果数值为零，那么它会为零，如果数值为负数，那么它会为-1，如果数值为正数，那么结果为1：
eg：
[sql]
SQL> select sign(-2),sign(0),sign(2) from dual;
SIGN(-2) SIGN(0) SIGN(2)
---------- ---------- ----------
-1 0 1
SQL>
9）cos（x）求数值的余弦值
10）acos(x）返回数字的反余弦值
三）转换函数：
1）to_char(x):把数字转换为字符串：
eg：
[sql]
SQL> select ename,'this sal is '||to_char(sal) from emp;
ENAME 'THISSALIS'||TO_CHAR(SAL)
---------- ----------------------------------------------------
WARD this sal is 1250
JONES this sal is 2975
MARTIN this sal is 1250
BLAKE this sal is 2850
SCOTT this sal is 3000
KING this sal is 5000
TURNER this sal is 1500
ADAMS this sal is 1100
JAMES this sal is 950
FORD this sal is 3000
MILLER this sal is 2222
11 rows selected.
SQL>
2）to_number(x)把字符串转换为数字：
eg：
[sql]
SQL> select to_number('-$21,222.33','$99,999.99') from dual;
TO_NUMBER('-$21,222.33','$99,999.99')
-------------------------------------
-21222.33
SQL>
3）cast（x as type）;该函数用于指定x为type兼容性的类型;
eg:
[sql]
SQL> select cast('1234' AS VARCHAR2(20)) || 'hello' from dual;
CAST('1234'ASVARCHAR2(20)
-------------------------
1234hello
SQL>
4）asciistr(x):将任意字符串转换为
数据库字符集的ASCII字符串
5）bin_to_number（x）：将二进制数字x转换为number类型。