ALTER TABLE scm_material_contract ADD CONSTRAINT material_contract_foreignid FOREIGN KEY(form_id) REFERENCES scm_purchase_contract(contract_id) ALTER TABLE scm_material_contract_add ADD CONSTRAINT material_contract_add_foreignid FOREIGN KEY(form_id) REFERENCES scm_purchase_contract_add(sub_contract_id) ALTER TABLE scm_material_settle_sd ADD CONSTRAINT material_settle_foreignid FOREIGN KEY(form_id) REFERENCES scm_sd_settle(settle_id) ALTER TABLE scm_material_settle_yd ADD CONSTRAINT material_settle_yd_foreignid FOREIGN KEY(form_id) REFERENCES scm_yd_settle(settle_id)
删除外键：
alter table product drop foreign key product_ibfk_1
原文：https://www.cnblogs.com/hoge66/p/12310886.html