mysql studio를 쓰지 않아서 잘 모르겠지만 터미널에서는 잘 되는 것 같습니다.

[root@db1 ~]# mysql -u root  -p test
Enter password:
Reading table information for completion of table and column names
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Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 14
Server version: 5.1.73 Source distribution

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Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> DROP TABLE N_Filter;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE N_Filter (PROCESS_TIME NVARCHAR(50), GMT_PROCESS_TIME NVARCHAR(50));
Query OK, 0 rows affected (0.01 sec)

mysql> desc N_Filter;
+------------------+-------------+------+-----+---------+-------+
| Field            | Type        | Null | Key | Default | Extra |
+------------------+-------------+------+-----+---------+-------+
| PROCESS_TIME     | varchar(50) | YES  |     | NULL    |       |
| GMT_PROCESS_TIME | varchar(50) | YES  |     | NULL    |       |
+------------------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> ALTER TABLE N_Filter ADD TZ_PROCESS_TIME NVARCHAR(50) Null AFTER GMT_PROCESS_TIME;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc N_Filter;
+------------------+-------------+------+-----+---------+-------+
| Field            | Type        | Null | Key | Default | Extra |
+------------------+-------------+------+-----+---------+-------+
| PROCESS_TIME     | varchar(50) | YES  |     | NULL    |       |
| GMT_PROCESS_TIME | varchar(50) | YES  |     | NULL    |       |
| TZ_PROCESS_TIME  | varchar(50) | YES  |     | NULL    |       |
+------------------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> ALTER TABLE N_Filter MODIFY PROCESS_TIME NVARCHAR(50) AFTER GMT_PROCESS_TIME;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc N_Filter;
+------------------+-------------+------+-----+---------+-------+
| Field            | Type        | Null | Key | Default | Extra |
+------------------+-------------+------+-----+---------+-------+
| GMT_PROCESS_TIME | varchar(50) | YES  |     | NULL    |       |
| PROCESS_TIME     | varchar(50) | YES  |     | NULL    |       |
| TZ_PROCESS_TIME  | varchar(50) | YES  |     | NULL    |       |
+------------------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)