Due to warehousing limitations, inventory over 800 units needs to be sent to an external storage site and tracked separately. You have been asked to monitor when an update will exceed this boundary so it can be addressed in production meetings.

1. Write a trigger titled "tgrExcessInventory" for the Production.ProductInventory table to ensure the quantity can never exceed 800 units.
2. Modify the trigger created in step 1 to execute its check code only if the Quantity column is updated.