Oracle 数值函数

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

--  向下取整，结果为：5
select floor(5.534) from dual;
select trunc(5.534) from dual;

--  向上取整，结果为：6
select ceil(5.534) from dual;
 
--  四舍五入，结果分别为：6,  6,  5.5,  5.53
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;

--保留N位小数（不四舍五入）按位数截取，结果分别为：5,   5.5,    5.53
select trunc(5.534,0) from dual;
select trunc(5.534,1) from dual;
select trunc(5.534,2) from dual;

--数字格式化，结果分别为： 12345.2, 12345.16, 12345.156, 12345.1560
select to_char(12345.156,'99999999.9') from dual;
select to_char(12345.156,'99999999.99') from dual;
select to_char(12345.156,'99999999.999') from dual;
select to_char(12345.156,'99999999.9999') from dual;

--  自动补零，结果分别为：12345.1000, 12345.1200, 12345.1230, 12345.1234
select to_char(12345.1,'99999999.9900') from dual;
select to_char(12345.12,'99999999.9900') from dual;
select to_char(12345.123,'99999999.9900') from dual;
select to_char(12345.1234,'99999999.9900') from dual;

-- 结果分别为: .1230, 0.1230
select to_char(0.123,'99999999.9900') from dual;
select to_char(0.123,'99999990.9900') from dual;