第四节 修改表结构之alter

-- 添加字段和外键：ALTER...ADD...
ALTER TABLE t_student ADD birthday DATETIME;
ALRER TABLE t_student ADD FOREIGN KEY (t_student_id) REFERENCES good_id;

-- 修改字段的数据类型和约束：ALTER...MODIFY...
ALTER TABLE t_student MODIFY birthday DATA NOT NULL;

-- 修改字段名：ALTER...CHANGE...
ALTER TABLE t_student CHANGE birthday birth DATE;

-- 删除字段：alter...drop...
ALTER TABLE t_student DROP birthday;