第一步输入show databases;
第二部 use day15;
第三部创造一个along的表
mysql> create table along(
-> id int, -> name varchar(20), -> gender int(2), -> birthday date, -> email int (20), -> remark varchar(50) -> );Query OK, 0 rows affected+-----------------+
| Tables_in_day15 |+-----------------+| along || stydent |+-----------------+2 rows in set第四部在查询一下 show tables;
第五部 在员工基本表上加age列;
alter table along add age int;
代码如上 along名字add 加age 后面定属性
第六部:查询 desc along;
效果图 这个就是表的效果图 上面的 写的代码都在里面
mysql> desc along;
+----------+-------------+------+-----+---------+-------+| Field | Type | Null | Key | Default | Extra |+----------+-------------+------+-----+---------+-------+| id | int(11) | YES | | NULL | || name | varchar(20) | YES | | NULL | || gender | int(2) | YES | | NULL | || birthday | date | YES | | NULL | || email | int(20) | YES | | NULL | || remark | varchar(50) | YES | | NULL | || age | int(11) | YES | | NULL | |+----------+-------------+------+-----+---------+-------+第7步 联系 修改email 的列长度为50的;
mysql>代码: alter table along modify email int(50);
mysql>查询一下: desc along;
+----------+-------------+------+-----+---------+-------+| Field | Type | Null | Key | Default | Extra |+----------+-------------+------+-----+---------+-------+| id | int(11) | YES | | NULL | || name | varchar(20) | YES | | NULL | || gender | int(2) | YES | | NULL | || birthday | date | YES | | NULL | || email | int(50) | YES | | NULL | || remark | varchar(50) | YES | | NULL | || age | int(11) | YES | | NULL | |+----------+------------已经从10变50了 email的
联系(3) 删除remark 的列
代码:alter table along drop remark;
mysql> 在查询一下:desc along;
+----------+-------------+------+-----+---------+-------+| Field | Type | Null | Key | Default | Extra |+----------+-------------+------+-----+---------+-------+| id | int(11) | YES | | NULL | || name | varchar(20) | YES | | NULL | || gender | int(2) | YES | | NULL | || birthday | date | YES | | NULL | || email | int(50) | YES | | NULL | || age | int(11) | YES | | NULL | |+----------+-------------+------+-----+---------+-------+就没有那个了列了:联系4 列名 name 修改为 username;
代码:alter table along change name username varchar(20);
mysql>查询: desc along;
| id | int(11) | YES | | NULL | || username | varchar(20) | YES | | NULL | || gender | int(2) | YES | | NULL | || birthday | date | YES | | NULL | || email | int(50) | YES | | NULL | || age | int(11) | YES | | NULL | |+----------+--以上 就改了。。。name 改成 username。