feat: create order with transaction for OrderItems and Products update

task.sql

@@ -1,11 +1,64 @@
--- Use our database
-USE ShopDB; 
+DROP DATABASE IF EXISTS ShopDB;
 
--- Some data should be created outside the transaction (here)
+CREATE DATABASE ShopDB;
+USE ShopDB;
 
--- Start the transaction 
-START TRANSACTION; 
+CREATE TABLE Products (
+    ID INT AUTO_INCREMENT,
+    Name VARCHAR(50),
+    Description VARCHAR(100),
+    Price INT,
+    WarehouseAmount INT,
+    PRIMARY KEY (ID)
+);
 
--- And some data should be created inside the transaction 
+CREATE TABLE Customers (
+    ID INT AUTO_INCREMENT,
+    FirstName VARCHAR(50),
+    LastName VARCHAR(50),
+    Email VARCHAR(50),
+    Address VARCHAR(50),
+    PRIMARY KEY (ID)
+);
 
-COMMIT; 
+CREATE TABLE Orders (
+    ID INT AUTO_INCREMENT,
+    CustomerID INT,
+    FOREIGN KEY (CustomerID) REFERENCES Customers(ID) ON DELETE SET NULL,
+    Date DATE,
+    PRIMARY KEY (ID)
+);
+
+CREATE TABLE OrderItems (
+    ID INT AUTO_INCREMENT,
+    OrderID INT,
+    FOREIGN KEY (OrderID) REFERENCES Orders(ID) ON DELETE SET NULL,
+    ProductID INT,
+    Count INT,
+    FOREIGN KEY (ProductID) REFERENCES Products(ID) ON DELETE SET NULL,
+    PRIMARY KEY (ID)
+);
+
+INSERT INTO Products (Name, Description, Price, WarehouseAmount)
+    VALUES ('AwersomeProduct', 'Product Desctiption', 5, 42);
+
+INSERT INTO Customers (FirstName, LastName, Email, Address)
+    VALUES ('John', 'Dou', 'j@dou.ua', 'far, far away');
+
+-- Order is created outside the transaction: an empty order can exist
+-- independently and does not require atomicity with stock changes.
+INSERT INTO Orders (CustomerID, Date)
+    VALUES (1, '2023-01-01');
+
+-- Adding an item to the order and decreasing stock must be atomic:
+-- both must succeed together, or neither should be applied.
+START TRANSACTION;
+
+INSERT INTO OrderItems (OrderID, ProductID, Count)
+    VALUES (LAST_INSERT_ID(), 1, 1);
+
+UPDATE Products
+    SET WarehouseAmount = WarehouseAmount - 1
+    WHERE ID = 1;
+
+COMMIT;