Oracle之数字函数


		Oracle之数字函数
 
用oracle sql对数字进行操作: 取上取整、向下取整、保留N位小数、四舍五入、数字格式化 
 
取整（向下取整）： 
select floor(5.534) from dual; 
select trunc(5.534) from dual; 
上面两种用法都可以对数字5.534向下取整，结果为5. 
 
如果要向上取整 ，得到结果为6，则应该用ceil 
select ceil(5.534) from dual; 
 
四舍五入： 
SELECT round(5.534) FROM dual; 
SELECT round(5.534,0) FROM dual; 
SELECT round(5.534,1) FROM dual; 
SELECT round(5.534,2) FROM dual; 
结果分别为 6, 6, 5.5, 5.53 
 
保留N位小数（不四舍五入）： 
select trunc(5.534,0) from dual; 
select trunc(5.534,1) from dual; 
select trunc(5.534,2) from dual; 
结果分别是 5,5.5,5.53，其中保留0位小数就相当于直接取整了。 
 
数字格式化： 
select to_char(12345.123,'99999999.9999') from dual; 
结果为12345.123 
 
select to_char(12345.123,'99999999.9900') from dual; 
小数后第三第四为不足补0，结果为12345.1230 
 
select to_char(0.123,'99999999.9900') from dual; 
select to_char(0.123,'99999990.9900') from dual; 
结果分别为 .123, 0.123