WHERE columnName IS NULL but not getting expected result

Question

I just started my first project for my portfolio and I'm totally confused...

During the EDA process, I noticed that the Continent column with a NULL value is perfect for queries specifically targeting continents, since the corresponding population column has the total population regardless of date.

So I want to only view the country (location column) by filtering out the NULL values ​​in the continent column:

SELECT 
    *
FROM
    covidDeaths
WHERE continent IS NOT NULL
ORDER BY
    date asc;

However, when I do this, the NULL values ​​still show up in the results table.

Answer 1

My guess is that these values ​​are not NULL, but empty strings.