Third Normal Form (3NF) in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the SQL code to select all columns from the table named 'Employees'.

SQL

SELECT [1] FROM Employees;

Drag options to blanks, or click blank then click option'

A*

BALL

CALL_COLUMNS

DEVERYTHING

Attempts:

3 left

💡 Hint

Common Mistakes

Using keywords like ALL or ALL_COLUMNS which are not valid in SELECT.

Trying to write column names when you want all columns.

In SQL, * means select all columns from the table.

2fill in blank

medium

Complete the SQL code to create a table named 'Orders' with a primary key column 'OrderID'.

SQL

CREATE TABLE Orders (OrderID INT [1], OrderDate DATE);

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AUNIQUE

BINDEX

CFOREIGN KEY

DPRIMARY KEY

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNIQUE instead of PRIMARY KEY, which is similar but not the main key.

Confusing FOREIGN KEY with PRIMARY KEY.

The PRIMARY KEY constraint uniquely identifies each record in the table.

3fill in blank

hard

Fix the error in the SQL code to remove partial dependencies and achieve 3NF by creating a new table for customer details.

SQL

CREATE TABLE Orders (OrderID INT PRIMARY KEY, CustomerID INT, [1] VARCHAR(100));

Drag options to blanks, or click blank then click option'

AOrderDate

BCustomerName

CProductID

DOrderAmount

Attempts:

3 left

💡 Hint

Common Mistakes

Keeping CustomerName in Orders table causing partial dependency.

Removing columns unrelated to customer details.

CustomerName depends on CustomerID, so it should be moved to a separate table to avoid partial dependency and achieve 3NF.

4fill in blank

hard

Fill both blanks to create a new table 'Customers' with CustomerID as primary key and CustomerName as a column.

SQL

CREATE TABLE Customers ([1] INT [2], CustomerName VARCHAR(100));

Drag options to blanks, or click blank then click option'

ACustomerID

BPRIMARY KEY

CFOREIGN KEY

DUNIQUE

Attempts:

3 left

💡 Hint

Common Mistakes

Using FOREIGN KEY instead of PRIMARY KEY here.

Using UNIQUE without PRIMARY KEY for the main identifier.

CustomerID is the column name and PRIMARY KEY defines it as the unique identifier for the Customers table.

5fill in blank

hard

Fill all three blanks to create a foreign key relationship from Orders to Customers on CustomerID.

SQL

ALTER TABLE Orders ADD CONSTRAINT [1] FOREIGN KEY ([2]) REFERENCES [3](CustomerID);

Drag options to blanks, or click blank then click option'

Afk_customer

BCustomerID

CCustomers

DOrderID

Attempts:

3 left

💡 Hint

Common Mistakes

Using OrderID instead of CustomerID as foreign key.

Referencing wrong table name in REFERENCES clause.

The constraint name is 'fk_customer', the foreign key column is 'CustomerID', and it references the 'Customers' table.