mysql dba系统学习（20）mysql存储引擎MyISAM

1，创建myisam表

mysql> create table t (id int , name varchar(30) , msg varchar(100)) engine = MyISAM;
mysql> show table status like "t" G ;
*************************** 1. row ***************************
Name: t
Engine: MyISAM
Version: 10
Row_format: Dynamic
Rows: 0
Avg_row_length: 0
Data_length: 0
Max_data_length: 281474976710655
Index_length: 1024
Data_free: 0
Auto_increment: NULL
Create_time: 2013-09-12 00:39:29
Update_time: 2013-09-12 00:39:29
Check_time: NULL
Collation: utf8_general_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)

2,auto_increment

当使用这个参数的时候，这个列一定要是主键

mysql> create table tt (id int auto_increment primary key  , name varchar(30) , msg varchar(100)) engine = MyISAM;
Query OK, 0 rows affected (0.01 sec)
mysql> insert into tt(name,msg) values('chenzhongyang','good');
Query OK, 1 row affected (0.00 sec)
虽然我们没有指定名字是chenzhongyang的id是1，但是有了auto_increment这个参数，系统会自动给他加上1
mysql> select * from tt;
+----+---------------+------+
| id | name          | msg  |
+----+---------------+------+
|  1 | chenzhongyang | good |
+----+---------------+------+
1 row in set (0.01 sec)

我们还可以设置auto_increment的值，但是这个值设置了的话，就会从这个值开始累积

mysql> alter table tt auto_increment=2000;
Query OK, 1 row affected (0.02 sec)
Records: 1  Duplicates: 0  Warnings: 0
mysql> insert into tt(name,msg) values('tianhongyan','baby');
Query OK, 1 row affected (0.00 sec)
mysql> select * from tt;
+------+---------------+------+
| id   | name          | msg  |
+------+---------------+------+
|    1 | chenzhongyang | good |
| 2000 | tianhongyan   | baby |
+------+---------------+------+
2 rows in set (0.00 sec)
mysql> insert into tt(name,msg) values('zhongguo','XXXXXXX-YYYYYYYYY-+VVVV');
Query OK, 1 row affected (0.00 sec)
mysql> select * FROM tt;
+------+---------------+-------------------------+
| id   | name          | msg                     |
+------+---------------+-------------------------+
|    1 | chenzhongyang | good                    |
| 2000 | tianhongyan   | baby                    |
| 2001 | zhongguo      | XXXXXXX-YYYYYYYYY-+VVVV |
+------+---------------+-------------------------+
3 rows in set (0.00 sec)

还有一个函数比较有用last_insert_id()。这个函数可以查出最后一次insert的id

mysql> select  last_insert_id();
+------------------+
| last_insert_id() |
+------------------+
|             2001 |
+------------------+
1 row in set (0.00 sec)

3，存储结构

数据文件(.MYD),索引文件(.MYI)和结构文件(.frm)

特点:可以在不同服务器上拷贝数据文件和索引文件。

如果我们把索引文件和数据文件放到不同的机器上，那么可以提高系统i/o

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