如何在mysql中添加外键（与python的连接器）

Question

我有这部分 python 脚本来创建表到 mysql db

#Product
TABLES['product'] = (
"CREATE TABLE product"
 "(prod_id smallint,"
  "name varchar(255),"
  "price int,"
  "constraint pk_prod_id primary key (prod_id)"
 ");")

#Sales
TABLES['sales'] = (
"CREATE TABLE sales"
 "(sales_id smallint,"
  "name varchar(255),"
  "quantity int,"
  "buy_id smallint,"
  "date DATE,"  
  "constraint pk_sales_id primary key (sales_id,name)"
 ");")
#Purchase
TABLES['purchase'] = (
"CREATE TABLE purchase"
 "(purchase_id smallint,"
  "name varchar(255),"
  "quantity int,"
  "sup_id smallint,"
  "date DATE,"  
  "constraint pk_purchase_id primary key (purchase_id,name)"
  ");")

# Adding foreign key
query =  'ALTER TABLE sales ADD foreign key(buy_id) references buyers(buy_id)'
cursor.execute(query)
query = 'ALTER TABLE purchase ADD foreign key(sup_id) references suppliers(sup_id)'
cursor.execute(query)

直到这里它工作正常，但这是主要问题。

query = 'ALTER TABLE sales ADD foreign key(name) references product(name)'
cursor.execute(query)
query = 'ALTER TABLE purchase ADD foreign key(name) references product (name)'
cursor.execute(query)

错误码是1215，所以不能添加外键

如果我这样做，它会起作用

query = ('ALTER TABLE sales ADD foreign key(prod_id) references product(prod_id)')
cursor.execute(query)
query = ('ALTER TABLE purchase ADD foreign key(prod_id) references product(prod_id)')
cursor.execute(query)

但我更喜欢使用 name 而不是 prod_id，因为它一团糟。

我该如何解决这个问题？我尝试使用 int 类型，但我不喜欢这种解决方案，而且我必须重写很多查询。

Answer 1

用 KEY (name) 制作这样的表格产品

#Product
TABLES['product'] = (
"CREATE TABLE product"
 "(prod_id smallint,"
  "name varchar(255),"
  "price int,"
  "constraint pk_prod_id primary key (prod_id),"
  "KEY (name)"
 ");")

您可以在没有探针的情况下为产品名称添加外键

Answer 2

谢谢你，它有效。 但是以前的查询现在不再起作用了 例如，我可以这样做；

cursor = cnx.cursor()
date = str(input('insert a date in yyyy-mm-dd :'))
query = "SELECT SUM(DISTINCT p.price*s.quantity),COUNT(p.price*s.quantity) FROM product p JOIN sales s ON  p.name = s.name WHERE s.date > "
cursor.execute(query+"'"+date+"'")

for i,j in cursor:
    print("Number of sales {}\nMoney earned {}".format(j,i))

结果是这样的

insert a date in yyyy-mm-dd :2019-06-03
Number of sales 5
Money earned 12750

现在这不再起作用了。