一、trunc截取數字，小數位舍去，整數位取0，不進行四舍五入
TRUNC(n1, n2) n1要處理的數字，n2保留的位數(默認是舍棄所有小數位)
SELECT TRUNC(123.45) FROM DUAL; # 123
SELECT TRUNC(123.45, 0) FROM DUAL; # 123
SELECT TRUNC(123.45, 1) FROM DUAL; # 123.4
SELECT TRUNC(123.45, 2) FROM DUAL; # 123.45
- 結果
二、to_char格式化小數，把數字轉變為字符串，進行四舍五入
SELECT TO_CHAR(123.45) FROM DUAL; # 123.45
SELECT TO_CHAR(123.45, '999') FROM DUAL; # 123
SELECT TO_CHAR(123.45, '999.9') FROM DUAL; # 123.5
SELECT TO_CHAR(123.45, '999.99') FROM DUAL; # 123.45
- 結果
三、round對數字進行四舍五入,默認是舍入小數位
SELECT ROUND(123.45) FROM DUAL; # 123
SELECT ROUND(123.45, 0) FROM DUAL; # 123
SELECT ROUND(123.45, 1) FROM DUAL; # 123.5
SELECT ROUND(123.45, 2) FROM DUAL; # 123.45
- 結果
四、cast轉為指定位數的number,注意number的第一個參數是轉換之后整數加小數的總位數
SELECT CAST(123.45 AS NUMBER(3)) FROM DUAL; # 123
SELECT CAST(123.45 AS NUMBER(4, 1)) FROM DUAL; # 123.5
SELECT CAST(123.45 AS NUMBER(5, 2)) FROM DUAL; # 123.45
- 結果
