General error: 3780 Referencing column 'invoice_id' and referenced column 'id' in foreign key constraint 'disccent_EarlyPaymentRecurring_ibfk_3' are incompatible.
Symptom
When updating to WHMCS 8.9, you may see the following error:
Unable to complete incremental updates: Unable to import the 8.9.0 Beta1 database file. Unable to import /path/to/whmcs/resources/sql/upgrade890beta1.sql: SQLSTATE[HY000]: General error: 3780 Referencing column 'invoice_id' and referenced column 'id' in foreign key constraint 'disccent_EarlyPaymentRecurring_ibfk_3' are incompatible.
Cause
An after-market module "Discount Center" from the vendor ModulesGarden appears to add a table in the WHMCS database named disccent_EarlyPaymentRecurring.
This table contains indexes with foreign key constraints related to the stock tblinvoices
table. These constraints prevent the altering of the tblinvoices
table during the 8.9 update process.
![](https://media.screensteps.com/image_assets/assets/008/174/737/original/4082a489-c47e-4d09-8742-f20b9e0aaabc.png)
Workaround
The module vendor has provided a workaround. Please see the Discount Center upgrade instructions.
We suggest contacting the vendor's support directly for further assistance. The ModulesGarden support team can be contacted here; https://www.modulesgarden.com/support