Magento 2 : Foreign key constraint is incorrectly formed, ALTER TABLE customer_group

Question

After upgrade from magento 2.1.7 to 2.2.3 and am stuck. I have tried everything.

In Pdo.php line 235:
SQLSTATE[HY000]: General error: 1025 Error on rename of './zwwnzwzjhe/#sql-1bd1_25f9' to './zwwnzwzjhe/customer_group' (errno: 150 - Foreign key constraint is incorrectly formed), query was: ALTER TABLE customer_group MODIFY COLUMN customer_group_id int(10) UNSIGNED NOT NULL AUTO_INCREMENT

In Pdo.php line 228: SQLSTATE[HY000]: General error: 1025 Error on rename of './zwwnzwzjhe/#sql-1bd1_25f9' to './zwwnzwzjhe/customer_group' (errno: 150 - Foreign key constraint is incorrectly formed)

I am unable to delete this table or make any changes to this table ...please help.

Thank you

Answer 1

To work around this, use either of these solutions. Both present risks of damaging the data integrity.

Option 1:

Remove constraints
Perform TRUNCATE
Delete manually the rows that now have references to nowhere
Create constraints

Option 2:

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