MySQL中的表中增加删除字段?

迈不过友情╰ 2022-05-21 10:25 220阅读 0赞

mysql> create table id\_name(id int,name varchar(20));  
Query OK, 0 rows affected (0.13 sec)  
  
  
mysql> alter table id\_name add age int,add address varchar(11);  
Query OK, 0 rows affected (0.13 sec)  
Records: 0  Duplicates: 0  Warnings: 0  
  
mysql> desc id\_name；  
  
\+---------+-------------+------+-----+---------+-------+  
| Field   | Type        | Null | Key | Default | Extra |  
\+---------+-------------+------+-----+---------+-------+  
| id      | int(11)     | YES  |     | NULL    |       |  
| name    | varchar(20) | YES  |     | NULL    |       |  
| age     | int(11)     | YES  |     | NULL    |       |  
| address | varchar(11) | YES  |     | NULL    |       |  
\+---------+-------------+------+-----+---------+-------+  
rows in set (0.00 sec)  
  
2.删除两个字段  
mysql> alter table id\_name drop column age,drop column address;  
Query OK, 0 rows affected (0.14 sec)  
Records: 0  Duplicates: 0  Warnings: 0  
  
mysql> desc id\_name;  
\+-------+-------------+------+-----+---------+-------+  
| Field | Type        | Null | Key | Default | Extra |  
\+-------+-------------+------+-----+---------+-------+  
| id    | int(11)     | YES  |     | NULL    |       |  
| name  | varchar(20) | YES  |     | NULL    |       |  
\+-------+-------------+------+-----+---------+-------+  
rows in set (0.00 sec)  
  
3.插入  
mysql> insert into id\_name values (1,'qustdjx');  
Query OK, 1 row affected (0.00 sec)  
4.查询看一下  
mysql> alter table id\_name add age int,add address varchar(11);  
Query OK, 1 row affected (0.07 sec)  
Records: 1  Duplicates: 0  Warnings: 0  
  
mysql> select \* from id\_name;  
\+------+---------+------+---------+  
| id   | name    | age  | address |  
\+------+---------+------+---------+  
|    1 | qustdjx | NULL | NULL    |  
\+------+---------+------+---------+  
row in set (0.00 sec)  
5.新增字段并插入  
mysql> insert into id\_name values(2,'qust',14,'山东');  
Query OK, 1 row affected (0.00 sec)  
  
mysql> select \* from id\_name;  
\+------+---------+------+---------+  
| id   | name    | age  | address |  
\+------+---------+------+---------+  
|    1 | qustdjx | NULL | NULL    |  
|    2 | qust    |   14 | 山东    |  
\+------+---------+------+---------+  
rows in set (0.00 sec)