Question

我已经编写了一个类似于

的h2 db的查询

SELECT o.order_id,  o.order_date , o.petrol_qty,  (o.price) as price_per_litre , (o.price * petrol_qty) as total_Price, t.truck_code
 FROM ORDERZ o left join truck t ON o.truck_id = t.truck_id
group by o.order_id

结果如此这是一个orderz表

ORDER_ID ORDER_DATE PETROL_QTY PRICE_PER_LITRE  TOTAL_PRICE     TRUCK_CODE  
1       2005-01-01     12.0     5.8                69.6           BY2354
2       2006-01-21     13.0     2.8                36.4           BY2994
3       2006-01-21     13.0     2.8                36.4           BY8754
4       2006-01-21     13.0     2.8                36.4           BY8754
5       2006-01-21     13.0     2.8                36.4           BY2354

在卡车表中我希望每辆卡车每月获得平均汽油量（汽油应该是订单表中的汽油数量）我被卡住了，因为我不确切地知道如何为每辆卡车做一个月平均值，请帮忙。

这些是我的表

CREATE TABLE truck (
  truck_id INT NOT NULL AUTO_INCREMENT,
  truck_code VARCHAR(255) NOT NULL,
  purchased_date VARCHAR(255) NOT NULL,
  description VARCHAR(255) NOT NULL,
  PRIMARY KEY (truck_id)
);

DROP TABLE IF EXISTS order;

CREATE TABLE IF NOT EXISTS orderz (
  order_id INT NOT NULL AUTO_INCREMENT,
  petrol_qty DOUBLE NOT NULL,
  price DOUBLE NOT NULL DEFAULT 0,
  order_date  Date NOT NULL,
  truck_id INT,
  PRIMARY KEY (order_id),
  FOREIGN KEY (truck_id) REFERENCES truck(truck_id)
  ON UPDATE CASCADE
  ON DELETE CASCADE
);

NOte- truck_code是唯一的我想要卡车表看起来像 truck_id truck_code avg_amount_petrol_qty_per_month，我只使用h2 db

Answer 1

H2 DB文档具有以下功能：MONTH(date)，YEAR(date)和聚合函数AVG()。可以使用MONTHNAME（日期）而不是MONTH（日期）。试试这个？

A）按卡车代码分组，年份和月份：

select t.truck_code, year(order_date) as year, month(order_date) as month,
avg(petrol_qty) as avg_petrol_qty from
truck t inner join orderz o
on t.truck_id = o.truck_id 
group by t.truck_code, year(order_date), month(order_date)
order by t.truck_code, year(order_date), month(order_date)

B）按卡车代码和月份分组：

select t.truck_code,  month(order_date) as month,
avg(petrol_qty) as avg_petrol_qty from
truck t inner join orderz o
on t.truck_id = o.truck_id 
group by t.truck_code,   month(order_date)
order by t.truck_code,   month(order_date)

计算sql中每月的平均订单量

1 个答案: