Solution

task.sql

@@ -1,33 +1,75 @@
--- Create database and tables
+-- Database Normalization Task
+-- ShopDB - Online Shop Database (3NF Normalized)
 
+-- Drop the database if it exists
+DROP DATABASE IF EXISTS ShopDB;
+
+-- Create the database
 CREATE DATABASE ShopDB;
 USE ShopDB;
 
+-- Create Countries table (already in 3NF)
 CREATE TABLE Countries (
-    ID INT,
-    Name VARCHAR(50),
-    PRIMARY KEY (ID)
+    ID INT AUTO_INCREMENT PRIMARY KEY,
+    Name VARCHAR(255) NOT NULL UNIQUE
+);
+
+-- Create Products table (2NF: separate product information)
+CREATE TABLE Products (
+    ID INT AUTO_INCREMENT PRIMARY KEY,
+    ProductName VARCHAR(255) NOT NULL UNIQUE
+);
+
+-- Create Warehouses table (2NF: separate warehouse information)
+CREATE TABLE Warehouses (
+    ID INT AUTO_INCREMENT PRIMARY KEY,
+    WarehouseName VARCHAR(255) NOT NULL,
+    WarehouseAddress VARCHAR(255) NOT NULL,
+    CountryID INT NOT NULL,
+    FOREIGN KEY (CountryID) REFERENCES Countries(ID),
+    UNIQUE KEY unique_warehouse (WarehouseName, WarehouseAddress)
 );
 
+-- Create ProductInventory table (3NF: only inventory-specific data)
 CREATE TABLE ProductInventory (
-    ID INT,
-    ProductName VARCHAR(50),
-    WarehouseAmount INT,
-    WarehouseName VARCHAR(50),
-    WarehouseAddress VARCHAR(50), 
-    CountryID INT,
-	FOREIGN KEY (CountryID) REFERENCES Countries(ID) ON DELETE NO ACTION,
-    PRIMARY KEY (ID)
+    ID INT AUTO_INCREMENT PRIMARY KEY,
+    ProductID INT NOT NULL,
+    WarehouseID INT NOT NULL,
+    Amount INT NOT NULL DEFAULT 0,
+    FOREIGN KEY (ProductID) REFERENCES Products(ID),
+    FOREIGN KEY (WarehouseID) REFERENCES Warehouses(ID),
+    UNIQUE KEY unique_product_warehouse (ProductID, WarehouseID)
 );
 
--- Populate test data
-
-INSERT INTO Countries (ID,Name)
-	VALUES (1, 'Country1');
-INSERT INTO Countries (ID,Name)
-	VALUES (2, 'Country2');
-
-INSERT INTO ProductInventory (ID,ProductName,WarehouseAmount,WarehouseName,WarehouseAddress,CountryID)
-	VALUES (1, 'AwersomeProduct', 2, 'Warehouse-1', 'City-1, Street-1',1);
-INSERT INTO ProductInventory (ID,ProductName,WarehouseAmount,WarehouseName,WarehouseAddress,CountryID)
-	VALUES (2, 'AwersomeProduct', 5, 'Warehouse-2', 'City-2, Street-2',2);
+-- Insert test data into Countries
+INSERT INTO Countries (Name) VALUES
+('Ukraine'),
+('Poland'),
+('Germany'),
+('USA');
+
+-- Insert test data into Products
+INSERT INTO Products (ProductName) VALUES
+('Laptop Dell XPS 13'),
+('iPhone 14 Pro'),
+('Samsung Galaxy S23'),
+('MacBook Pro 16'),
+('iPad Air'),
+('Surface Pro 9');
+
+-- Insert test data into Warehouses
+INSERT INTO Warehouses (WarehouseName, WarehouseAddress, CountryID) VALUES
+('Main Warehouse Kyiv', '123 Khreshchatyk St, Kyiv', 1),
+('Warehouse Lviv', '456 Svobody Ave, Lviv', 1),
+('Warsaw Central', '321 Marszałkowska St, Warsaw', 2),
+('Berlin Storage', '987 Unter den Linden, Berlin', 3),
+('New York Depot', '258 Broadway, New York', 4);
+
+-- Insert test data into ProductInventory
+INSERT INTO ProductInventory (ProductID, WarehouseID, Amount) VALUES
+-- Minimal test data - exactly 5 records
+(1, 1, 50),  -- Laptop Dell XPS 13 in Kyiv
+(2, 2, 30),  -- iPhone 14 Pro in Lviv
+(3, 3, 25),  -- Samsung Galaxy S23 in Warsaw
+(4, 4, 15),  -- MacBook Pro 16 in Berlin
+(5, 5, 40);  -- iPad Air in New York