I need to delete all data in a single field from 300 tables

[Kaibito]

I have an ecommerce store that I am currently working on and there are approx 300 products which have a field named "product_id" at www.prescription-glasses.com database.

These fields contains an old product_id that I need to delete altogether.

How can I create a query that will replace all "product_id" fields with data in them with a null value?

[Lakeville]

This will set every product_id to NULL which is currently not null.

UPDATE table_name
SET product_id= NULL
WHERE product_id is not null;