customer 客户表 ord 订单表 item 产品表
CREATE TABLE customer(
id int not NULL PRIMARY KEY,
cust_name VARCHAR(20) not NULL
);
CREATE TABLE cust_order(
id int not NULL PRIMARY KEY,
cust_id int not NULL,
buy_time date
);
CREATE TABLE item(
id int not NULL PRIMARY KEY,
ord_id int not NULL,
item_name VARCHAR(100) not NULL
);
查询谁买了多少商品
SELECT item_name 商品名称 FROM item,customer,cust_order
WHERE item.ord_id=cust_order.id
AND customer.id=cust_order.cust_id
AND cust_name='李特'；```
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