alter table tbl_name add col_name type

mysql>alter table pet add weight int;

alter table tbl_name drop col_name

mysql>alter table pet drop weight;

alter table tbl_name modify col_name type

mysql>alter table pet modify weight varchar(30);

alter table tbl_name change old_col_name col_name type

alter table pet change weight weight varchar(30);

alter table tbl_name change old_col_name col_name

mysql>alter table pet change weight wei;

alter table tbl_name rename new_tbl

mysql>alter table pet rename animal;

mysql> ALTER TABLE user
      -> MODIFY COLUMN pwd VARCHAR NOT NULL DEFAULT ‘666666';

mysql> ALTER TABLE user
     -> ALTER COLUMN pwd varchar not null SETDEFAULT 5;

CREATETABLE IF NOT EXISTS dictionary (  
  id int(10) unsigned NOT NULLAUTO_INCREMENT,
  word varchar(100) NOT NULL,
  mean varchar(300) NOT NULL,
   PRIMARY KEY (`id`)
   );  

mysql>DELIMITER $$
mysql>DROP PROCEDURE IF EXISTS SampleProc$$
Query OK, 0rows affected, 1 warning (0.01 sec)
CREATEPROCEDURE SampleProc()
BEGIN
DECLARE xINT;
SET x = 1;
WHILEx  <= 110000 DO
insert intodictionary (word, mean) values(concat('a',x),concat('a means',x));
SET  x = x + 1;
END WHILE;
END
mysql>    DELIMITER ;
mysql>call SampleProc();

mysql> flush status;
Query OK, 0 rows affected (0.00 sec)
mysql> alter table dictionary
      ->modify column mean varchar(20) NOT null default 'DEFAULT1';
Query OK, 110002 rows affected (3.07 sec)
Records: 110002 Duplicates: 0 Warnings: 0
mysql> SHOW STATUS WHERE Variable_name LIKE'Handler%'
  ->OR Variable_name LIKE 'Created%';
+----------------------------+--------+
| Variable_name       | Value |
+----------------------------+--------+
| Handler_read_rnd_next   | 110003 |
| Handler_rollback      | 0   |
| Handler_savepoint     | 0   |
| Handler_savepoint_rollback | 0   |
| Handler_update       | 0   |
| Handler_write       | 110002 |
+----------------------------+--------+

 mysql> flush status;
mysql> alter table dictionary
     -> alter column mean set default'DEFAULT2';
Query OK, 0 rowsaffected (0.03 sec)
Records: 0 Duplicates: 0 Warnings: 0
 mysql> SHOW STATUSWHERE Variable_name LIKE 'Handler%'
     -> OR Variable_name LIKE 'Created%';
+----------------------------+-------+
| Variable_name       | Value |
+----------------------------+-------+
|Handler_read_rnd_next   | 0   |
|Handler_savepoint_rollback | 0   |
| Handler_update       | 0   |
| Handler_write       | 0   |

mysql>create table dictionary_new like dictionary;

mysql> alter table dictionary_new
     -> modify column mean varchar(30)default 'DEFAULR#';
mysql> flush table with read lock;

       mysql> unlock tables;
       mysql> insert into dictionary(word) values('Random');
       mysql> select * from dictionarywhere word='Random'；

+--------+--------+----------+
| id   | word | mean   |
+--------+--------+----------+
| 110004 |Random | DEFAULR# |
+--------+--------+----------+