ALTER TABLE for_fornecedor ADD COLUMN percentual_csll numeric (18,6);
ALTER TABLE for_fornecedor ADD COLUMN percentual_pis numeric (18,6);
ALTER TABLE for_fornecedor ADD COLUMN percentual_cofins numeric (18,6);

UPDATE for_fornecedor SET percentual_csll = 0   WHERE percentual_csll   IS NULL;
UPDATE for_fornecedor SET percentual_pis = 0    WHERE percentual_pis    IS NULL;
UPDATE for_fornecedor SET percentual_cofins = 0 WHERE percentual_cofins IS NULL;

ALTER TABLE for_fornecedor ALTER COLUMN percentual_csll SET NOT NULL;
ALTER TABLE for_fornecedor ALTER COLUMN percentual_pis SET NOT NULL;
ALTER TABLE for_fornecedor ALTER COLUMN percentual_cofins SET NOT NULL;