Oracle中sql直接处理数字的几种方式

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.

向上取整

select ceil(5.534) from dual;

保留N位小数（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