NOT NULL constraint in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a NOT NULL constraint to the 'name' column.

SQL

ALTER TABLE employees MODIFY COLUMN name [1];

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AVARCHAR(50) NOT NULL

BVARCHAR(50)

CINT NOT NULL

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to specify the data type when modifying the column.

Using a wrong data type like INT for a name column.

The NOT NULL constraint ensures the 'name' column cannot have NULL values. The column type must be specified along with NOT NULL.

2fill in blank

medium

Complete the code to create a table where 'email' cannot be NULL.

SQL

CREATE TABLE users (id INT PRIMARY KEY, email [1]);

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AVARCHAR(100)

BINT NOT NULL

CTEXT

DVARCHAR(100) NOT NULL

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting NOT NULL, allowing NULL emails.

Using INT type for email.

The NOT NULL constraint on 'email' ensures every user must have an email address.

3fill in blank

hard

Fix the error in the code to add a NOT NULL constraint to 'age'.

SQL

ALTER TABLE persons MODIFY age [1];

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AINT NOT NULL

BVARCHAR(3) NOT NULL

CINT

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Specifying only NOT NULL without data type.

Using wrong data type like TEXT for age.

The correct syntax requires specifying the data type with NOT NULL to modify the column properly.

4fill in blank

hard

Fill both blanks to create a table where 'username' and 'password' cannot be NULL.

SQL

CREATE TABLE accounts (username [1], password [2]);

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AVARCHAR(30) NOT NULL

BVARCHAR(30)

CTEXT NOT NULL

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving one column without NOT NULL.

Using TEXT without NOT NULL.

Both 'username' and 'password' columns must have NOT NULL constraints with appropriate data types.

5fill in blank

hard

Fill all three blanks to add NOT NULL constraints to 'title', 'author', and 'year' columns.

SQL

CREATE TABLE books (title [1], author [2], year [3]);

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AVARCHAR(100) NOT NULL

BVARCHAR(50) NOT NULL

CINT NOT NULL

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Using TEXT without NOT NULL.

Using wrong data types for columns.

Each column has a suitable data type with NOT NULL to ensure no missing values.