Question

我有一个问题。如果给我一张带有正数和负数的表格，并且我想分别查找所有正数的总数和所有负数的总数并将其显示在一行中。我能够提出一种解决方案（如下）。我想检查一下使用Select和CASE语句是否有更好的解决方案

struct S {
    int a;
    int b;
    friend ostream& operator<<(ostream& _os, const S& _s) { 
        _os << _s.a << ' ' << _s.b << endl; 
        return _os; 
    }
};

我的解决方案：

id  amount
1   100
2   -10
3   50
4   -80
5   20
6   -20

positive negative
170         -110

Answer 1

使用条件聚合：https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=e2fa9cc6aee27cc501c9cda98bc2cf2d

SELECT
    SUM(CASE WHEN amount > 0 THEN amount END) AS positive,
    SUM(CASE WHEN amount < 0 THEN amount END) AS negative
FROM #temp;

输出：

positive    negetive
170         -110

Answer 2

您还可以使用sign()来确定它是正数还是负数

select  sum(case when sign(amount) = 1 then amount end),
        sum(case when sign(amount) = -1 then amount end)
from    #temp

Answer 3

这将起作用：

1）对于SQL Server

SELECT
    SUM(IIF(amount > 0, amount, 0)) positive,
    SUM(IIF(amount < 0, amount, 0)) negative
FROM TABLENAME;

2）对于SQL Server和MySQL

SELECT
    SUM(CASE WHEN amount > 0 THEN amount END) positive,
    SUM(CASE WHEN amount < 0 THEN amount END) negative
FROM TABLENAME;

仅使用select和case语句分别内联查找正数和负数的总数

3 个答案: