homework

task.sql

@@ -1,33 +1,65 @@
--- Create database and tables
+-- Drop the existing database if it exists
+DROP DATABASE IF EXISTS ShopDB;
 
+-- Create a new database
 CREATE DATABASE ShopDB;
+
+-- Use the new database
 USE ShopDB;
 
+-- Create the normalized tables
+-- Table for countries (already normalized)
 CREATE TABLE Countries (
-    ID INT,
-    Name VARCHAR(50),
-    PRIMARY KEY (ID)
+    ID INT AUTO_INCREMENT PRIMARY KEY,
+    Name VARCHAR(50) NOT NULL
+);
+
+-- Normalized Products table to hold product details
+CREATE TABLE Products (
+    ID INT AUTO_INCREMENT PRIMARY KEY,
+    Name VARCHAR(100) NOT NULL
 );
 
-CREATE TABLE ProductInventory (
-    ID INT,
-    ProductName VARCHAR(50),
-    WarehouseAmount INT,
-    WarehouseName VARCHAR(50),
-    WarehouseAddress VARCHAR(50), 
+-- Normalized Warehouses table to remove transitive dependencies
+-- This table stores all warehouse information in one place
+CREATE TABLE Warehouses (
+    ID INT AUTO_INCREMENT PRIMARY KEY,
+    Name VARCHAR(100) NOT NULL,
+    Address VARCHAR(255) NOT NULL,
     CountryID INT,
-	FOREIGN KEY (CountryID) REFERENCES Countries(ID) ON DELETE NO ACTION,
-    PRIMARY KEY (ID)
+    FOREIGN KEY (CountryID) REFERENCES Countries(ID) ON DELETE SET NULL
+);
+
+-- Normalized ProductInventories table to link products and warehouses
+-- This is a join table that resolves a many-to-many relationship and stores the quantity
+CREATE TABLE ProductInventories (
+    ProductID INT NOT NULL,
+    WarehouseID INT NOT NULL,
+    WarehouseAmount INT NOT NULL,
+    PRIMARY KEY (ProductID, WarehouseID),
+    FOREIGN KEY (ProductID) REFERENCES Products(ID) ON DELETE CASCADE,
+    FOREIGN KEY (WarehouseID) REFERENCES Warehouses(ID) ON DELETE CASCADE
 );
 
--- 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);
+-- Populate the normalized tables with test data
+-- Insert countries
+INSERT INTO Countries (Name) VALUES
+('Ukraine'),
+('USA');
+
+-- Insert products
+INSERT INTO Products (Name) VALUES
+('AwesomeProduct'),
+('CoolProduct');
+
+-- Insert warehouses
+INSERT INTO Warehouses (Name, Address, CountryID) VALUES
+('Warehouse-1', 'City-1, Street-1', 1),
+('Warehouse-2', 'City-2, Street-2', 2);
+
+-- Insert product inventories
+INSERT INTO ProductInventories (ProductID, WarehouseID, WarehouseAmount) VALUES
+(1, 1, 2),
+(1, 2, 5),
+(2, 1, 3),
+(2, 2, 7);