如何在Derby数据库的双列中设置精度? [英] How can I set up precision in a double column in Derby database?

问题描述

我正在使用这些代码在derby数据库中创建一个表.

I am using these codes to create a table in derby database.

    CREATE TABLE "USED_BANKACCOUNT"
    (
       "FYEAR" VARCHAR(10),
        "NUM" DOUBLE,
       "USERNAME" VARCHAR(20)
        );

我的数据是这样存储的.

My data is stored like this.

   FYEAR              NUM                  USERNAME
   ---------------------------------------------------
   2013               10.5                 Pranjal
   2013               5.25                 Pranjal
   2013               9.0                  Bimal 
   ---------------------------------------------------

但是我希望这样存储我的数据

But I want my data to be stored like this

   FYEAR              NUM                  USERNAME
   ---------------------------------------------------
   2013               10.50                 Pranjal
   2013               5.25                  Pranjal
   2013               9.00                  Bimal 
   ---------------------------------------------------

我应该如何处理 DOUBLE 数据类型?

What should I do with my DOUBLE datatype ?

推荐答案

使用DECIMAL 类型:

Use a DECIMAL type with a defined precision and scale:

CREATE TABLE "USED_BANKACCOUNT" (
    "FYEAR" VARCHAR(10),
    "NUM" DECIMAL(5, 2),
    "USERNAME" VARCHAR(20)
);

precision 表示数字中所允许的总位数(小数点的左侧和右侧)，而 scale 则表示数字的位数允许的小数位数.因此，上面的示例定义了一个十进制数字，该数字最多允许5位数字，而小数部分为2位数字.

The precision represents the total number of digits allowed in the number(both to the left and the right of the decimal poin), and the scale represents the number of fractional digits allowed. So the above example defines a decimal number that will allow a maximum of 5 digits, with 2 digits in the fractional component.

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