Add trigger to automatically calculate subtotal price of cart

app/services/product_service.py

@@ -6,42 +6,42 @@ class ProductService:
 
 	@staticmethod
 	def get_name(product_id: int):
-		cursor.execute(f"select name from product where product.product_id = {product_id}")
+		cursor.execute(f"select name from product where product.id = {product_id}")
 		result = cursor.fetchone()
 		return result['name']
 
 	@staticmethod
 	def get_manufacturer(product_id: int):
-		cursor.execute(f"select manufacturer from product where product.product_id = {product_id}")
+		cursor.execute(f"select user.displayname as seller from product inner join user on product.seller_id = user.id where product.id = {product_id}")
 		result = cursor.fetchone()
-		return result['manufacturer']
+		return result['seller']
 
 	@staticmethod
 	def get_price(product_id: int):
-		cursor.execute(f"select price_pc from product where product.product_id = {product_id}")
+		cursor.execute(f"select price_pc from product where product.id = {product_id}")
 		result = cursor['price_pc']
 		return result[0]
 
 	@staticmethod
 	def get_image(product_id: int):
-		cursor.execute(f"select image from product where product.product_id = {product_id}")
+		cursor.execute(f"select image from product where product.id = {product_id}")
 		result = cursor['image']
 		return base64.b64encode(result[0]).decode('utf-8')
 
 	@staticmethod
 	def get_image_name(product_id: int):
-		cursor.execute(f"select image_name from product where product.product_id = {product_id}")
+		cursor.execute(f"select image_name from product where product.id = {product_id}")
 		result = cursor['image_name']
 		return result[0]
 
 	@staticmethod
 	def get_all_info(product_id: int):
-		cursor.execute(f"select name,manufacturer,price_pc,image_name,image from product where product.product_id = {product_id}")
+		cursor.execute(f"select name, user.displayname as seller, price_pc, image_name, image from product inner join user on product.seller_id = user.id where product.id = {product_id}")
 		result = cursor.fetchone()
 
 		return {
 			"name": result['name'],
-			"manufacturer": result['manufacturer'],
+			"seller": result['seller'],
 			"price": result['price_pc'],
 			"image_name": result['image_name'],
 			"image": base64.b64encode(result['image']).decode('utf-8')

app/services/user_service.py

@@ -232,7 +232,7 @@ class UserService:
 		:rtype: bool
 		"""
 		displayname_regex = r"^[a-zA-Z.-_]{1,64}$"
-		return re.match(username_regex, displayname)
+		return re.match(displayname_regex, displayname)
 
 	@staticmethod
 	def __verify_username(username: str) -> bool:

shop.sql

@@ -121,12 +121,27 @@ after delete
 on cart_item for each row
 begin
 	update cart
-	set price_total = (
-		select sum(price_subtotal)
+	set price_total = ifnull(
+		(select sum(price_subtotal)
 		from cart_item
-		where cart_id = old.cart_id
+		where cart_id = old.cart_id),
+		0.00
 	)
 	where id = old.cart_id;
 end;
 //
-delimiter;
+delimiter;
+
+delimiter //
+create trigger calculate_price_subtotal
+before insert on cart_item
+for each row
+begin
+	set new.price_subtotal = (
+		select new.count * p.price_pc
+		from product p
+		where p.id = new.product_id
+	);
+END;
+//
+DELIMITER ;