这是您的表和联接的整套答案 .

Customer

CREATE TABLE customer (

customer_id int NOT NULL PRIMARY KEY AUTO_INCREMENT,

name varchar(50),

address varchar(100)

) ENGINE=InnoDB;

Product

CREATE TABLE product (

product_id int NOT NULL PRIMARY KEY AUTO_INCREMENT,

name varchar(50)

) ENGINE = InnoDB;

Bought or Transactions

CREATE TABLE bought (

id int NOT NULL PRIMARY KEY AUTO_INCREMENT,

product_id int,

customer_id int,

FOREIGN KEY (product_id) REFERENCES product(product_id),

FOREIGN KEY (customer_id) REFERENCES customer(customer_id)

) ENGINE=InnoDB;

INSERT values

INSERT INTO customer (name, address) VALUEs ("George","Kentucky")

INSERT INTO customer (name, address) VALUEs ("Stan","Dublin")

INSERT INTO customer (name, address) VALUEs ("Kazaam","UAE")

INSERT INTO customer (name, address) VALUEs ("Sarah","New York")

INSERT INTO product (name) VALUES ("tomato")

INSERT INTO product (name) VALUES ("apple")

INSERT INTO bought (customer_id, product_id) VALUEs("1","2")

INSERT INTO bought (customer_id, product_id) VALUEs("2","1")

INSERT INTO bought (customer_id, product_id) VALUEs("3","1")

INSERT INTO bought (customer_id, product_id) VALUEs("4","1")

Inner Join with Filter - >这将是您的$查询

SELECT customer.customer_id, customer.name as customer_name, product.name as product_name

FROM customer

INNER JOIN bought ON customer.customer_id = bought.customer_id

INNER JOIN product ON product.product_id = bought.product_id

WHERE product.name LIKE "apple" AND product.name NOT LIKE "tomato"

ORDER BY customer.name

这将过滤所有购买苹果的顾客 . 您所要做的就是更改 product.name 值 . 如果要更改字段，请更改 INNER JOIN 的第一行 .

Explanation of Venn Diagram: 如果你要考虑它，MySQL正在遵循维恩图的设计 . 它不能与3个对象相交并过滤它们 . 你试图通过在中间构建另一个圆圈来超越维恩图的设计 . 见下图 .

因此，为了解决PHP上的问题，我们创建了这个内圈 . 您运行循环以获取product_name上具有“apples”的所有customer_id . 然后再次执行一个mysql_fetch数组循环 . 并仅使用“apples”输出customer_ids .

如果你无法通过MySQL解决过滤问题，可以通过过滤数据来解决它 .