取整（向下取整） select floor(5.534) from dual; select trunc(5.534) from dual; 上面兩種用法都可以對數字5.534向下取整，結果為5. 如果要向上取整 ，得到結果為6，則應該用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; 結果分別為 6, 6, 5.5, 5.53 保留N位小數（不四舍五入）按位數截取 select trunc(5.534,0) from dual; select trunc(5.534,1) from dual; select trunc(5.534,2) from dual; 結果分別是 5,5.5,5.53，其中保留0位小數就相當於直接取整了。 數字格式化 select to_char(12345.123,'99999999.9999') from dual; 結果為12345.123
select to_char(12345.123,'99999999.9900') from dual; 小數后第三第四為不足補0，結果為12345.1230
select to_char(0.123,'99999999.9900') from dual; select to_char(0.123,'99999990.9900') from dual; 結果分別為 .123, 0.123
