CustomerID

Country

Name

Gender

Removing duplicate entries and standardizing data formats

Extracting data from multiple operational databases

Loading data into the data warehouse

Creating surrogate keys for dimension tables

Star Schema

Aggregated Fact Table

Detailed Fact Table

Dimension Table

Stores summarized data about various dimensions

Contains non-numeric attributes describing entities

Stores business transactions or measurements, typically numeric

Contains surrogate keys for all dimensions

SELECT RestaurantName, DishName FROM Dishes LEFT JOIN Restaurants ON Restaurants.RestaurantID = Dishes.RestaurantID;

SELECT RestaurantName, DishName FROM Dishes FULL JOIN Restaurants ON Dishes.RestaurantID = Restaurants.RestaurantID;

SELECT RestaurantName, DishName FROM Dishes RIGHT JOIN Restaurants ON Dishes.RestaurantID = Restaurants.RestaurantID;

SELECT RestaurantName, DishName FROM Restaurants INNER JOIN Dishes ON Restaurants.RestaurantID = Dishes.RestaurantID;

Only products with assigned suppliers will be listed.

All suppliers will be listed, even if they have no products.

An error will be generated due to missing suppliers.

SELECT ProductID, SUM(Quantity) FROM Orders GROUP BY ProductID;

SELECT ProductID, COUNT(Quantity) FROM Orders GROUP BY ProductID HAVING COUNT(Quantity) > 100;

SELECT ProductID, SUM(Quantity) FROM Orders GROUP BY ProductID HAVING SUM(Quantity) > 100;

SELECT ProductID, SUM(Quantity) FROM Orders WHERE SUM(Quantity) > 100 GROUP BY ProductID;

SELECT * FROM Employees FULL JOIN Departments ON Employees.DepartmentID = Departments.DepartmentID;

SELECT * FROM Employees RIGHT JOIN Departments ON Employees.DepartmentID = Departments.DepartmentID;

ELECT * FROM Employees INNER JOIN Departments ON Employees.DepartmentID = Departments.DepartmentID;

SELECT * FROM Employees LEFT JOIN Departments ON Employees.DepartmentID = Departments.DepartmentID;

SELECT DISTINCT CustomerID FROM Orders WHERE YEAR(OrderDate) = 2025

SELECT CustomerID FROM Orders GROUP BY OrderDate;

SELECT CustomerID FROM Orders WHERE OrderDate LIKE '2025%';

SELECT DISTINCT CustomerID FROM Orders WHERE OrderDate >= '2025-01-01';

3NF

2NF

1NF