Resolved: What is the explanation for not truncate the table?

Hi Mohamed!
Thanks for reaching out.

You cannot TRUNCATE a table that has FK constraints applied on it (TRUNCATE is not the same as DELETE). Please, use the following code:

SET FOREIGN_KEY_CHECKS = 0; 
TRUNCATE table departments; 
SET FOREIGN_KEY_CHECKS = 1;

Hope this helps.
Best,
Tsvetelin