Java Derby SQL 连接

Question

我有 3 张桌子：

应用-

ID (PK)
DEVELOPER
GENRE
DESCRIPTION
POPULARITY
COST

客户 -

ID (PK)
FIRSTNAME
SURNAME
ADDRESS
TOWN
POSTCODE
PROFESSION

CUSTOMER_PURCHASES -

TRANSACTION_ID (PK)
CUSTOMER_ID (FK)
APPLICATION_ID (FK)

我有一种方法可以让客户购买应用程序。该方法使用自动生成的 Transaction_ID + CUSTOMER_ID（由客户表提供）+ APPLICATION_ID（由应用程序表提供）填充表 CUSTOMER_PURCHASES。

我需要提供输出的 SQL 语句 -

Transaction ID: 501
Customer ID: 301
Name: Beatrice May
Application ID: 302
Application Cost: £1.00

我的 SQL 查询不起作用：

SELECT TRANSACTION_ID,
       CUSTOMER.ID,
       CUSTOMER_ID,
       FIRSTNAME, 
       SURNAME, 
       APPLICATION_ID, 
       APPLICATION.COST 
FROM CUSTOMER, CUSTOMER_PURCHASES,APPLICATION WHERE CUSTOMER.ID = CUSTOMER_PURCHASES.CUSTOMER_ID

谢谢

詹姆斯

Answer 1

使用显式连接语法

SELECT TRANSACTION_ID,
       CUSTOMER.ID,
       CONCAT(FIRSTNAME, ' ',  SURNAME) AS Name, 
       APPLICATION.ID, 
       APPLICATION.COST 
FROM CUSTOMER
JOIN CUSTOMER_PURCHASES
ON CUSTOMER.ID = CUSTOMER_PURCHASES.CUSTOMER_ID
JOIN APPLICATION 
ON APPLICATION.ID = CUSTOMER_PURCHASES.APPLICATION_ID