当我将78.9插入Mysql(使用JDBC)时,它会被舍入到79？这是正常的吗？

Question

当我将78.9插入Mysql(使用JDBC)时,它会被舍入到79？这是正常的......如果是这样的话我怎么能阻止这种情况发生.

更多细节:

列名:num 数据类型:decimal(12,0) *以上项目是从phpMyAdmin复制的

查询是

stmt.executeUpdate("INSERT INTO triples(sub_id, pro_id, num) VALUES("+subId+","+proId+",78.9)");

理想情况下,我会使用变量而不是硬编码的78.9

如

        BigDecimal obj = new BigDecimal(78.9);

Answer 1

这是正常的,因为使用十进制(0,0)中的0基本上表示小数点后应该没有任何内容,因此它会向上舍入.您需要指定比例以获得您想要的内容.例如,十进制(12,5)将允许小数点左边的7个数字和右边的五个数字.

The declaration syntax for a DECIMAL column is DECIMAL(M,D). 
The ranges of values for the arguments in MySQL 5.1 are as follows:

M is the maximum number of digits (the precision). 
It has a range of 1 to 65. (Older versions of MySQL permitted a range of 1 to 254.)

D is the number of digits to the right of the decimal point (the scale). 
It has a range of 0 to 30 and must be no larger than M.

请参阅:http://dev.mysql.com/doc/refman/5.1/en/precision-math-decimal-changes.html