MySQL Alter Command

root@host# mysql -u root -p password;
Enter password:*******
mysql> use TUTORIALS;
Database changed
mysql> create table testalter_tbl
    -> (
    -> i INT,
    -> c CHAR(1)
    -> );
Query OK, 0 rows affected (0.05 sec)
mysql> SHOW COLUMNS FROM testalter_tbl;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| i     | int(11) | YES  |     | NULL    |       |
| c     | char(1) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.00 sec)

ADVERTISEMENTS



						
Dropping, Adding or Repositioning a Column:

mysql> ALTER TABLE testalter_tbl  DROP i;

ADVERTISEMENTS



						

mysql> ALTER TABLE testalter_tbl ADD i INT;

						

mysql> SHOW COLUMNS FROM testalter_tbl;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| c     | char(1) | YES  |     | NULL    |       |
| i     | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.00 sec)

						

ALTER TABLE testalter_tbl DROP i;
ALTER TABLE testalter_tbl ADD i INT FIRST;
ALTER TABLE testalter_tbl DROP i;
ALTER TABLE testalter_tbl ADD i INT AFTER c;

						
Changing a Column Definition or Name:

mysql> ALTER TABLE testalter_tbl MODIFY c CHAR(10);

						

mysql> ALTER TABLE testalter_tbl CHANGE i j BIGINT;

						

mysql> ALTER TABLE testalter_tbl CHANGE j j INT;

						
The Effect of ALTER TABLE on Null and Default Value Attributes:

mysql> ALTER TABLE testalter_tbl 
    -> MODIFY j BIGINT NOT NULL DEFAULT 100;

						

mysql> ALTER TABLE testalter_tbl ALTER i DROP DEFAULT;
mysql> SHOW COLUMNS FROM testalter_tbl;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| c     | char(1) | YES  |     | NULL    |       |
| i     | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
2 rows in set (0.00 sec)

						
Changing a Table Type:

mysql> ALTER TABLE testalter_tbl TYPE = MYISAM;
mysql>  SHOW TABLE STATUS LIKE 'testalter_tbl'\G
*************************** 1. row ****************
           Name: testalter_tbl
           Type: MyISAM
     Row_format: Fixed
           Rows: 0
 Avg_row_length: 0
    Data_length: 0
Max_data_length: 25769803775
   Index_length: 1024
      Data_free: 0
 Auto_increment: NULL
    Create_time: 2007-06-03 08:04:36
    Update_time: 2007-06-03 08:04:36
     Check_time: NULL
 Create_options:
        Comment:
1 row in set (0.00 sec)

						
Renaming a Table:

mysql> ALTER TABLE testalter_tbl RENAME TO alter_tbl;