ALTER TABLE `fa_ps_workorder`
  ADD COLUMN `spec` varchar(100) NOT NULL DEFAULT '' COMMENT '规格，可不关联产品档案' AFTER `product_name`;

UPDATE `fa_ps_workorder` w
LEFT JOIN `fa_ps_product` p ON p.id = w.product_id
SET w.spec = IFNULL(p.spec, '')
WHERE w.spec = '' AND w.product_id > 0;