Sql 找到平均每日值

此表包含不同商店的日期和苹果价格。最后，我希望SQL报告结果“$3.5”，即两天内苹果的平均成本。如何修改下面的查询

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

数据：

---

按天分组，就像你已经做的那样，得到每天的总和，然后从结果中选择平均值

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;

---

您可以执行两次

avg

。使用where子句编写子查询以获取预期日期。要按日期获取

avg

，请在主查询中执行另一个

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

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

：

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

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

---

什么是

PnL

type？@D-Shih将其改为Apple cost以简化示例为什么结果是3.5而不是3？8-22平均值是3，8-23平均值是4。平均2人之间我写一个答案你可以试试@alan dennison