Learn SQL. 8 lesson bug or error?

#1

http://cropme.ru/f78f8269bb8ad6eeb72efdd74277cd1f

Delete all of the rows that have a NULL value in the twitter column. Above SELECT type

http://cropme.ru/fa6f095dfe3c15314748991e49a1ec4e

????????????????????????? help me please

#2

You weren't supposed to delete the code above, you were just supposed to write the code on 4,
if you still don't know what i mean check out my code:

UPDATE celebs
SET twitter_handle = '@taylorswift13'
WHERE id = 4;
DELETE FROM celebs WHERE twitter_handle IS NULL; /* This is where u went wrong */
SELECT * FROM celebs;

#3

I did just that and does not work

#4