Question

此表包含日期和在不同商店的苹果的价格。最终，我希望SQL报告结果“ $ 3.5”，这是两天内苹果的平均成本。如何在下面修改我的查询？

Select Date, sum(AppleCost) from table where Date between '2018-08-21' and '2018-08-22'
and group by Date;

数据：

[Date,AppleCost]

[08-22,$5]

[08-22,$1]

[08-23,$4]

Answer 1

像以前一样按天分组，以获取每天的总和，然后从该结果中选择平均值。

SELECT avg(pnl) pnl
       FROM (SELECT sum(totalpnl) pnl
                    FROM table
                    WHERE tradedate BETWEEN '2018-08-21'
                                            AND '2018-08-22'
                    GROUP BY tradedate) x;

Answer 2

您可以执行两次avg。编写子查询，使用where子句获取期望的日期。要按日期获取avg，请在主查询中再执行一次avg。

CREATE TABLE T
(
     DATE DATE,
     AppleCost INT
);

INSERT INTO T VALUES ('2018-08-22', 5);
INSERT INTO T VALUES ('2018-08-22', 1);
INSERT INTO T VALUES ('2018-08-23', 4);

查询1 ：

SELECT 
    AVG(dayAvg) 
FROM
    (SELECT DATE, AVG(AppleCost) dayAvg
     FROM T 
     WHERE DATE BETWEEN '2018-08-22' AND '2018-08-23'
     GROUP BY DATE) t

Results ：

| avg(dayAvg) |
|-------------|
|         3.5 |

寻找平均每日价值

2 个答案: