问高人：round()函数如何用？

Question

round(input_value,decimal_places_of_precision),例如：
SQL> select round(1234.5678,4) from dual;ROUND(1234.5678,4)
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         1234.5678SQL> select round(1234.5678,3) from dual;ROUND(1234.5678,3)
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          1234.568SQL> select round(1234.5678,2) from dual;ROUND(1234.5678,2)
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           1234.57SQL> select round(1234.5678,1) from dual;ROUND(1234.5678,1)
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            1234.6SQL> select round(1234.5678,0) from dual;ROUND(1234.5678,0)
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              1235SQL> select round(1234.5678,-1) from dual;ROUND(1234.5678,-1)
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               1230SQL> select round(1234.5678,-2) from dual;ROUND(1234.5678,-2)
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               1200SQL> select round(1234.5678,-3) from dual;ROUND(1234.5678,-3)
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               1000SQL>

Answer 1

round(x[,y])
返回舍入到小数点右边y位的x值,y的缺省值为0.y可以为负数,那么就舍入到小数点左边相应的位上,但y必须是整数.

Answer 2

四舍五入
SELECT ROUND (TO_DATE ('27-OCT-92'),'YEAR')
   "New Year" FROM DUAL;
 
New Year
---------
01-JAN-93 SELECT ROUND(15.193,1) "Round" FROM DUAL;     Round
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      15.2
SELECT ROUND(15.193,-1) "Round" FROM DUAL;     Round
----------
        20 

Answer 3

ROUND(X, Y) X 的 四 捨 五 入 值 ， 如 果 Y 是 正 數 ， 就 取 小 數 位 的 右 邊 ， 負 數 就 取 左 邊 
SQL> SELECT ROUND(1.5, 0), ROUND(0.15, 1), ROUND(15, -1) FROM DUAL;ROUND(1.5,0) ROUND(0.15,1) ROUND(15,-1)
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           2            .2           20