MySQL中的alter table命令的基本使用方法及提速优化

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: 0mysql> 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# |+--------+--------+----------+