ADD 新增

1. 登入 mariadb。

   [root@kvm3 ~]# mycli -uroot -p123qwe
   Connecting to socket /var/lib/mysql/mysql.sock, owned by user mysql
   MariaDB 10.5.16
   mycli 1.26.1
   Home: http://mycli.net
   Bug tracker: https://github.com/dbcli/mycli/issues
   Thanks to the contributor - Roland Walker
   

2. 使用資料庫 dyw。

   MariaDB root@(none):(none)> use dyw;
   You are now connected to database "dyw" as user "root"
   Time: 0.002s
   

3. 查看資料表 tbl 的欄位格式。

   MariaDB root@(none):dyw> desc tbl;
   +-----------------+--------------+------+-----+---------+----------------+
   | Field           | Type         | Null | Key | Default | Extra          |
   +-----------------+--------------+------+-----+---------+----------------+
   | id              | int(11)      | NO   | PRI | <null>  | auto_increment |
   | title           | varchar(100) | NO   |     | <null>  |                |
   | author          | varchar(40)  | NO   |     | <null>  |                |
   | submission_date | date         | YES  |     | <null>  |                |
   +-----------------+--------------+------+-----+---------+----------------+
   
   4 rows in set
   Time: 0.066s
   

4. ADD 在資料表 tbl 最前面增加一個欄位 ti，格式為 TINYINT。

   MariaDB root@(none):dyw> alter table tbl add ti tinyint first;
   You're about to run a destructive command.
   Do you want to proceed? (y/n): y
   Your call!
   Query OK, 0 rows affected
   Time: 0.068s
   

5. 再查看資料表 tbl 的欄位格式。

   MariaDB root@(none):dyw> desc tbl;
   +-----------------+--------------+------+-----+---------+----------------+
   | Field           | Type         | Null | Key | Default | Extra          |
   +-----------------+--------------+------+-----+---------+----------------+
   | ti              | tinyint(4)   | YES  |     | <null>  |                |
   | id              | int(11)      | NO   | PRI | <null>  | auto_increment |
   | title           | varchar(100) | NO   |     | <null>  |                |
   | author          | varchar(40)  | NO   |     | <null>  |                |
   | submission_date | date         | YES  |     | <null>  |                |
   +-----------------+--------------+------+-----+---------+----------------+
   
   5 rows in set
   Time: 0.027s
   

6. ADD 在資料表 tbl 欄位 id 後新加一個欄位 c，格式為一個字元 char(1)。

   MariaDB root@(none):dyw> alter table tbl add c char(1) after id;
   You're about to run a destructive command.
   Do you want to proceed? (y/n): y
   Your call!
   Query OK, 0 rows affected
   Time: 0.038s
   

7. 再查看資料表 tbl 的欄位格式。

   MariaDB root@(none):dyw> desc tbl;
   +-----------------+--------------+------+-----+---------+----------------+
   | Field           | Type         | Null | Key | Default | Extra          |
   +-----------------+--------------+------+-----+---------+----------------+
   | ti              | tinyint(4)   | YES  |     | <null>  |                |
   | id              | int(11)      | NO   | PRI | <null>  | auto_increment |
   | c               | char(1)      | YES  |     | <null>  |                |
   | title           | varchar(100) | NO   |     | <null>  |                |
   | author          | varchar(40)  | NO   |     | <null>  |                |
   | submission_date | date         | YES  |     | <null>  |                |
   +-----------------+--------------+------+-----+---------+----------------+
   
   6 rows in set
   Time: 0.021s