SQL trigger implementations - mysql

Question

I am trying to write a mySql trigger for a website database. The backend uses django framework.
def add_trigger():
trigger = "CREATE TRIGGER update_ppl_rating \
BEFORE INSERT ON demosite_peoplerating \
FOR EACH ROW \
BEGIN \
DECLARE total integer; \
DECLARE sum integer; \
DECLARE avg float; \
SELECT COUNT(*) INTO total FROM demosite_peoplerating GROUP BY apart_key HAVING apart_key = NEW.apart_key; \
SELECT SUM(rating) INTO total FROM demosite_peoplerating GROUP BY apart_key HAVING apart_key = NEW.apart_key; \
SET avg = sum/total; \
UPDATE demosite_ratingtable \
SET ppl_rating = avg \
FROM demosite_ratingtable \
WHERE apart_key = NEW.apart_key \
END;"
cursor = connection.cursor()
cursor.execute(trigger)
cursor.close()
Here is the database model related:
class RatingTable(models.Model):
apart_key = models.ForeignKey(
'ApartmentFeature',
on_delete=models.CASCADE,
unique=True,
primary_key=True
)
env_rating = models.FloatField()
ppl_rating = models.FloatField()
rest_05_count = models.IntegerField()
rest_1_count = models.IntegerField()
rest_2_count = models.IntegerField()
shop_05_count = models.IntegerField()
shop_1_count = models.IntegerField()
shop_2_count = models.IntegerField()
class PeopleRating(models.Model):
comment_id = models.AutoField(primary_key=True)
apart_key = models.ForeignKey(
'ApartmentFeature',
on_delete=models.CASCADE,
)
rating = models.IntegerField()
comment = models.CharField(max_length=200)
nick_name = models.CharField(max_length=200)
After running add_trigger(), mysql server replies:
django.db.utils.ProgrammingError: (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM demosite_ratingtable WHERE apart_key = NEW.apart_key END' at line 1")
Could you please any one give me tha idea to solve this?