mysql 修改字段示例

-- 表增加字段
ALTER TABLE  test_user
ADD COLUMN  user_id bigint not null default 0  comment '主表ID，外键关联' after main_id;
-- 表迁移数据
update test_user set user_id=main_id ;
-- 删除外键约束
ALTER TABLE test_user drop foreign key  FK_Reference_44;
ALTER TABLE test_user DROP INDEX FK_Reference_44;
-- 增加外键约束
alter table test_user 
add constraint FK_Reference_44 foreign key (user_id)
references biz_threeinone_test_situation (id) on delete restrict on update restrict;
-- 修改原字段备注
alter table test_user
modify column main_id bigint comment '对应主表ID，命名有误，废弃';