#1.添加字段
ALTER TABLE student ADD stuAge INT NOT NULL;
#2.修改字段
ALTER TABLE student CHANGE stuAge sAge VARCHAR (100)NOT NULL;
#3.修改表名
ALTER TABLE students RENAME student;
#4.刪除字段
ALTER TABLE student DROP sAge;



#1.添加唯一約束
ALTER TABLE grade 
ADD CONSTRAINT stuName UNIQUE KEY(stuName);
#2.刪除唯一約束
ALTER TABLE
 
 grade
DROP INDEX stuName;


#1.添加默認值約束 (地址默認北京)
ALTER TABLE student
ALTER COLUMN stuAddress SET DEFAULT ‘北京‘
#2.刪除默認值約束
ALTER TABLE student
ALTER COLUMN stuAddress DROP DEFAULT


#1.給student表中添加一個stuAge的字段
ALTER TABLE student ADD stuAge INT 
#2.給stuAge添加一個檢查約束，驗證是否可以成功
ALTER TABLE student ADD CONSTRAINT
 
 ck_stuAge CHECK (stuAge>=18)
#3.驗證stuAge字段的檢查約束是否成功
INSERT INTO student(stuName,stuGradeid,stuAge)
VALUES("陳七",1,17)
#4.刪除檢查約束是不成功的
ALTER TABLE student
DROP CONSTRAINT ck_stuAge


#1.刪除外鍵約束

ALTER TABLE student2
DROP FOREIGN KEY FK_Grade_Student_GradeId

#
ALTER TABLE student2 ADD CONSTRAINT FK_Grade_Student_GradeId FOREIGN
 
 KEY (stuGradeid) REFERENCES `grade`(gid)

對mysql數據庫進行增刪改查