使用 INNER JOIN 在 SQL 查询中出错

Question

我还在学习MySQl。这是关系型 DBMS :

CUSTOMER (CustID, CustName, AnnualRevenue)
TRUCK (TruckNumber, DriverName)
CITY (CityName, Population)
SHIPMENT (ShipmentNumber, CustID, Weight, Year, TruckNumber, CityName)

现在，我必须为这两个查询制定公式：

Total weight of shipments per year for each city.

Drivers who drove shipments to London but not Paris.

这些是我提出的查询： 1.

select sum(s.weight), s.year , c.city
from shipment s, city c
INNER JOIN CITY
on s.CityName = c.CityName

Answer 1

您正在混合使用旧方法来 JOIN table（您应该避免使用这种方法，因为没有明确说明连接列，这会让其他人感到困惑）：

FROM shipment s, city c

您应该将 select 中未聚合的列分组（年份、城市）。此外，最好为聚合列使用别名 (AS total_weight)

select sum(s.weight) AS total_weight, s.year , c.city
from shipment s
INNER JOIN CITY as c
on s.CityName = c.CityName
GROUP BY s.year, c.city

尝试解决第二个问题，有问题再回来。

使用 INNER JOIN 在 SQL 查询中出错

Getting error in SQL query using INNER JOIN

mysql

rdbms