问题描述
是时候再次从全能的堆栈溢出问题中提问了。所以我的问题是我正在 TKINTER 中进行开发，并且在应用程序的一个数据库中实现并集成了 2 个表。我希望我的餐桌产品在购物篮表上放置订单后更新，并且一旦调用 self.data_entry 方法就会更新。问题是当我的 stock_update 方法运行时，它会更新数据库，但它会清除其他产品的库存价值。我只是想知道我的 stock_update 方法是否有错误的更新 sql 的语法。
跑步前
| product_id | product_name | stock |
|---|---|---|
| 1 | product1 | 60 |
| 1 | product2 | 60 |
之后
| product_id | product_name | stock |
|---|---|---|
| 1 | product1 | 59 |
| 1 | product2 | NULL |
类 DatabaseHandler：
def data_entry(self,cust_id,prod_id,prod_name,delivery_type,quantity,delivery_cost,price,subtotal):
print("Data Entry Method is called")
connection = sqlite3.connect("anothertrial.db")
cursor = connection.cursor()
# YA "value" in the following line should be "values"
insert_query = "INSERT INTO basket(cust_id,product_id,subtotal) VALUES(?,?,?)"
cursor.execute(insert_query,(cust_id,subtotal))
connection.commit()
connection.close()
print("Data Entry Method is finished")
def connection(self):
print("Database is Now connected")
db_conn = sqlite3.connect("anothertrial.db")
cursor = db_conn.cursor()
my_query = "CREATE TABLE IF NOT EXISTS basket(order_id INTEGER PRIMARY KEY AUTOINCREMENT,cust_id TEXT,product_id INTEGER,prod_name TEXT,delivery_type TEXT,quantity TEXT,delivery_cost TEXT,price TEXT,subtotal TEXT,FOREIGN KEY (product_id) REFERENCES products(product_id)) "
cursor.execute(my_query)
db_conn.commit()
db_conn.close()
print("Database connection is finished")
def product_connection(self):
print("Product Table Creation Method")
db_connect = sqlite3.connect("anothertrial.db")
cursor = db_connect.cursor()
product_table_creation = "CREATE TABLE IF NOT EXISTS products(product_id INTEGER PRIMARY KEY AUTOINCREMENT," \
"product_name TEXT,stock INTEGER)"
cursor.execute(product_table_creation)
db_connect.commit()
db_connect.close()
print("Product Table has been created")
def stock_update(self):
print("Stock Update Method") # I use Print to Test My Method If It Will Run
db_connect = sqlite3.connect("anothertrial.db")
cursor = db_connect.cursor()
stock_update_query = "UPDATE products SET stock = stock - (SELECT quantity FROM basket WHERE " \
"basket.product_id = " \
"products.product_id) "
cursor.execute(stock_update_query)
db_connect.commit()
db_connect.close()
print("Stock Updated") # I use Print to Test My Method If It Will Run
def add_item(self):
global total
global delivery_charge
global chosen_item_id
product_id_dict = {"Gundam": 1,"Starwars": 2,"Paw Patrol": 3,"Peppa Pig": 4,"Cars disney": 5,"Teddy Bear": 6}
item_dict = {"": 0,"Gundam": 10,"Starwars": 20,"Paw Patrol": 30,"Peppa Pig": 15,"Cars disney": 15,"Teddy Bear": 10}
delivery_dict = {"Free Delivery": 0,"Standard": 2,"Express": 5}
delivery_type = self.delivery_opt_var.get()
item = self.product_name_var.get()
price = (self.prod_cost_var.get())
qty = self.quantity_var.get()
for product,cost in item_dict.items():
for delivery,charge in delivery_dict.items():
for selected_product,prod_id in product_id_dict.items():
if item == product and delivery == delivery_type and item == selected_product:
chosen_item_id = prod_id
delivery_charge = charge
price = cost
total = round(price * qty + delivery_charge,2)
self.product_id_var.set(chosen_item_id)
self.prod_cost_var.set(price)
self.delivery_charge_var.set(delivery_charge)
self.subtotal_var.set(total)
self.customer_basket.data_entry(self.order_cust_id_var.get(),self.product_id_var.get(),self.product_name_var.get(),self.delivery_opt_var.get(),self.quantity_var.get(),self.delivery_charge_var.get(),self.prod_cost_var.get(),self.subtotal_var.get())
解决方法
我修改了查询。希望这项工作：
stock_update_query = "UPDATE products SET stock = stock - (SELECT quantity FROM basket WHERE " \
"basket.product_id = " \
"products.product_id) " \
"WHERE EXISTS (SELECT quantity " \
"FROM basket "\
"WHERE product_id = products.product_id)"