[mysql] Alter table

 MySQL  kio.comwlqw18xbq.ap-northeast-2.rds.amazonaws.com:3306 ssl  kio  SQL >

desc topic;
+-------------+-------------+------+-----+---------+----------------+
| Field       | Type        | Null | Key | Default | Extra          |
+-------------+-------------+------+-----+---------+----------------+
| id          | int(11)     | NO   | PRI | NULL    | auto_increment |
| title       | varchar(30) | NO   |     | NULL    |                |
| description | text        | YES  |     | NULL    |                |
| created     | datetime    | NO   |     | NULL    |                |
| author_id   | int(11)     | YES  |     | NULL    |                |
+-------------+-------------+------+-----+---------+----------------+
5 rows in set (0.0064 sec)

 MySQL  kio.comwlqw18xbq.ap-northeast-2.rds.amazonaws.com:3306 ssl  kio  SQL >

alter table topic change column author_id author varchar(15) not null;
Query OK, 5 rows affected (0.0793 sec)

Records: 5  Duplicates: 0  Warnings: 0

 MySQL  kio.comwlqw18xbq.ap-northeast-2.rds.amazonaws.com:3306 ssl  kio  SQL > desc topic;
+-------------+-------------+------+-----+---------+----------------+
| Field       | Type        | Null | Key | Default | Extra          |
+-------------+-------------+------+-----+---------+----------------+
| id          | int(11)     | NO   | PRI | NULL    | auto_increment |
| title       | varchar(30) | NO   |     | NULL    |                |
| description | text        | YES  |     | NULL    |                |
| created     | datetime    | NO   |     | NULL    |                |
| author      | varchar(15) | NO   |     | NULL    |                |
+-------------+-------------+------+-----+---------+----------------+
5 rows in set (0.0062 sec)

 MySQL  kio.comwlqw18xbq.ap-northeast-2.rds.amazonaws.com:3306 ssl  kio  SQL >

alter table topic add profile varchar(200) null;   --> 맨 마지막 컬럼으로 추가

 MySQL  kio.comwlqw18xbq.ap-northeast-2.rds.amazonaws.com:3306 ssl  kio  SQL >

desc topic;
+-------------+--------------+------+-----+---------+----------------+
| Field       | Type         | Null | Key | Default | Extra          |
+-------------+--------------+------+-----+---------+----------------+
| id          | int(11)      | NO   | PRI | NULL    | auto_increment |
| title       | varchar(30)  | NO   |     | NULL    |                |
| description | text         | YES  |     | NULL    |                |
| created     | datetime     | NO   |     | NULL    |                |
| author      | varchar(15)  | NO   |     | NULL    |                |
| profile     | varchar(200) | YES  |     | NULL    |                |
+-------------+--------------+------+-----+---------+----------------+
6 rows in set (0.0058 sec)

cf. 특정 컬럼 다음으로 추가  :  AFTER `컬럼`;

cf. 맨 앞 컬럼으로 추가 : FIRST;

MySQL  kio.comwlqw18xbq.ap-northeast-2.rds.amazonaws.com:3306 ssl  kio  SQL > 

alter table topic change column author author varchar(15) null;

 MySQL  kio.comwlqw18xbq.ap-northeast-2.rds.amazonaws.com:3306 ssl  kio  SQL >

desc topic;
+-------------+--------------+------+-----+---------+----------------+
| Field       | Type         | Null | Key | Default | Extra          |
+-------------+--------------+------+-----+---------+----------------+
| id          | int(11)      | NO   | PRI | NULL    | auto_increment |
| title       | varchar(30)  | NO   |     | NULL    |                |
| description | text         | YES  |     | NULL    |                |
| created     | datetime     | NO   |     | NULL    |                |
| author      | varchar(15)  | YES  |     | NULL    |                |
| profile     | varchar(200) | YES  |     | NULL    |                |
+-------------+--------------+------+-----+---------+----------------+

cf.

mysql> alter table membertbl change memberid memberid char(20) not null;
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc membertbl;
+---------------+----------+------+-----+---------+-------+
| Field         | Type     | Null | Key | Default | Extra |
+---------------+----------+------+-----+---------+-------+
| memberid      | char(20) | NO   | PRI | NULL    |       |
| membername    | char(5)  | NO   |     | NULL    |       |
| memberaddress | char(20) | YES  |     | NULL    |       |
+---------------+----------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> alter table membertbl change membername membername char(20) not null;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc membertbl;
+---------------+----------+------+-----+---------+-------+
| Field         | Type     | Null | Key | Default | Extra |
+---------------+----------+------+-----+---------+-------+
| memberid      | char(20) | NO   | PRI | NULL    |       |
| membername    | char(20)  | NO   |     | NULL    |       |
| memberaddress | char(20) | YES  |     | NULL    |       |
+---------------+----------+------+-----+---------+-------+
3 rows in set (0.00 sec)