SQL Database Null and Type Essentials Quiz

When reviewing a column storing optional notes from users, you notice some rows contain no value at all. What concept represents this intentional 'no value'?

A team is checking incomplete records. They want to find entries where a phone number hasn’t been provided yet. Which comparison style should they rely on?

While designing a table, you want a column that always contains a number. Which type best fits this requirement?

A developer compares a column to NULL using =. The condition never seems to match. What explains this?

When storing product names, which data type generally fits best?

A user accidentally leaves a comment field blank. Which value reflects the difference between a blank string and a true NULL?

You want to record the date of a transaction. Which data type is designed for this purpose?

While analyzing customer records, you notice comparisons involving NULL return unexpected results. Which logical concept explains this?

Which statement correctly describes how numeric types behave?

A developer needs to store a true/false flag for whether a feature is enabled. Which type is suited for this binary choice?

When checking missing payment dates, why isn’t = NULL a valid condition?

A column holding temperature as decimal readings accidentally stores some text strings. What issue does this cause?

If a field must always contain a date, which constraint prevents NULL from being stored?

When storing price values, which type avoids storing unnecessary decimal precision?

Why might a birthdate column allow NULL by design?

Which statement is true about empty strings?

Why should dates be stored in proper DATE types instead of text?

A NULL combined with arithmetic, such as price + NULL, results in:

Which type is most appropriate for storing a yes/no preference?

In a report, comparing city = NULL returns no matches. What's the proper reasoning?

A column storing ratings from 1–5 should use which type?

A NULL inside a comparison like amount > NULL returns:

Which type stores decimal values with precise formatting, often needed in monetary applications?

NULL is often used because:

A customer record contains an optional middle name. Which condition retrieves rows where no middle name is stored?

SELECT * FROM customers WHERE middle_name IS NULL;

You want to list items that have an unspecified expiration date. What does this query find?

SELECT id FROM items WHERE expires_at IS NULL;

A user’s age may be missing. What rows match this query?

SELECT * FROM users WHERE age IS NOT NULL;

What type of values does this query retrieve?

SELECT score FROM results WHERE score > 50;

A table tracks timestamps when tasks finish. What result does this query produce?

SELECT id FROM tasks WHERE finished_at IS NOT NULL;

Consider this age filter. Which values qualify?

SELECT * FROM people WHERE age >= 18;

A department table stores optional manager IDs. What does this query return?

SELECT name FROM departments WHERE manager_id IS NULL;

This query checks product weights. What rows are returned?

SELECT * FROM products WHERE weight IS NULL;

What does this query filter out?

SELECT name FROM pets WHERE height IS NOT NULL;

Which values survive this filter?

SELECT salary FROM staff WHERE salary < 50000;

What rows match the following?

SELECT * FROM logs WHERE message IS NULL;

A movie record may lack a release year. Which rows appear here?

SELECT title FROM movies WHERE release_year IS NULL;

Which rows qualify under this numeric test?

SELECT score FROM exams WHERE score BETWEEN 60 AND 100;

What does this condition identify?

SELECT * FROM orders WHERE delivered_at IS NOT NULL;

Which rows match this comparison?

SELECT id FROM assets WHERE value > 0;

What group of rows does this query retrieve?

SELECT * FROM profiles WHERE bio IS NULL;