Java 如何在某些单元格上使用自定义操作的 CriteriaQuery SUM？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/21627704/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to use CriteriaQuery SUM of custom operation on some cells?
提问by ioreskovic
Consider you have table T, with fields A and B.
假设您有表 T，其中包含字段 A 和 B。
With regular SQL, I could do this:
使用常规 SQL，我可以这样做：
SELECT SUM(A * (100.0 - B) / 100.0) AS D FROM T;
And I would get exactly what I expect.
我会得到我所期望的。
However, I'm not sure how to do it with CriteriaQuery.
但是，我不确定如何使用 CriteriaQuery 来做到这一点。
I know how to do sum over 1 field, but not how to do sum over some math expression over multiple fields in a row.
我知道如何对 1 个字段求和，但不知道如何对连续多个字段的某些数学表达式求和。
采纳答案by wypieprz
The CriteriaBuilderinterface provides the following arithmetic functions:
该CriteriaBuilder接口提供以下算术函数：
- addition:
sum(a, b) - substraction:
diff(a, b) - multiplication:
prod(a, b) - division:
quot(a, b)
- 添加：
sum(a, b) - 减法：
diff(a, b) - 乘法：
prod(a, b) - 分配：
quot(a, b)
where abparameters can be an expression and/or literal.
其中ab参数可以是表达式和/或文字。
As for the query, here is an exampe written in a human readable form:
至于查询，这是一个以人类可读形式编写的示例：
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Number> q = cb.createQuery(Number.class);
Root<T> t = q.from(T.class);
// build SUM(A * (100.0 - B) / 100.0) expression
Expression<Double> diff = cb.diff(100.0, t.<Double>get("B"));
Expression<Double> prod = cb.prod(t.<Double>get("A"), diff);
Expression<Number> quot = cb.quot(prod, 100.0);
Expression<Number> sum = cb.sum(quot);
q.select(sum.alias("D"));
System.out.println(em.createQuery(q).getSingleResult());
You can also build the query as an one-liner:
您还可以将查询构建为单行：
q.select(cb.sum(cb.quot(cb.prod(t.<Double>get("A"), cb.diff(100.0, t.<Double>get("B"))), 100.0)).alias("D"));
I hope it clarifies your doubts.
我希望它能澄清你的疑惑。
