mysql資料庫引擎MyISAM和InnoDB的比較和使用場合
阿新 • • 發佈：2019-01-26
資料庫中資料管理的一種方式，MySQL支援插入式的儲存引擎，也就是說你同一資料庫中的資料表可以選擇不同儲存引擎
檢視mysql版本
mysql> select version();
+-----------+
| version() |
+-----------+
| 5.5.25a |
+-----------+
1 row in set檢視mysql引擎
mysql> show engines; +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | Engine | Support | Comment | Transactions | XA | Savepoints | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL | | MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO | | MyISAM | YES | MyISAM storage engine | NO | NO | NO | | BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO | | CSV | YES | CSV storage engine | NO | NO | NO | | MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO | | ARCHIVE | YES | Archive storage engine | NO | NO | NO | | InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES | | PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
mysql5.5版本預設的資料庫引擎是innoDB
最常見的資料庫引擎是InnoDB和MyISAM
MyISAM
ISAM執行讀取操作的速度很快，而且不佔用大量的記憶體和儲存資源。ISAM的兩個主要不足之處在於，它不 支援事務處理，也不能夠容錯，MyISAM除了提供ISAM裡所沒有的索引和欄位管理的大量功能，MyISAM還使用一種表格鎖定的機制，來優化多個併發的讀寫操作，其代價是你需要經常執行OPTIMIZE TABLE命令，來恢復被更新機制所浪費的空間。MYISAM強調了快速讀取操作。
InnoDB
在使用MYSQL的時候，你所面對的每一個挑戰幾乎都源於ISAM和MyISAM資料庫引擎不支援事務處理（transaction process）也不支援外來鍵。儘管要比ISAM和 MyISAM引擎慢很多，但是InnoDB包括了對事務處理和外來鍵的支援，這兩點都是前兩個引擎所沒有的。
兩種引擎的比較與使用場合
MyISAM型別不支援事務處理等高階處理，而InnoDB型別支援。
MyISAM型別的表強調的是效能，其執行數度比InnoDB型別更快，但是不提供事務支援，而InnoDB提供事務支援已經外部鍵等高階資料庫功能。
MyISAM格式的一個重要缺陷就是不能在表損壞後恢復資料
InnoDB 中不儲存表的具體行數，也就是說，執行select count(*) from table時，InnoDB要掃描一遍整個表來計算有多少行，但是MyISAM只要簡單的讀出儲存好的行數即可。注意的是，當count(*)語句包含where條件時，兩種表的操作是一樣的
MyISAM的索引和資料是分開的，並且索引是有壓縮的，記憶體使用率就對應提高了不少。能載入更多索引，而Innodb是索引和資料是緊密捆綁的，沒有使用壓縮從而會造成Innodb比MyISAM體積龐大
DELETE FROM table時，InnoDB不會重新建立表，而是一行一行的刪除
MyISAM適合：
(1)做很多count 的計算；
(2)插入不頻繁，查詢非常頻繁；
(3)沒有事務。
InnoDB適合：
(1)可靠性要求比較高，或者要求事務；
(2)表更新和查詢都相當的頻繁，並且表鎖定的機會比較大的情況指定資料引擎的建立
更改一個表的資料庫引擎
查看錶結構
mysql> describe cds;
+-----------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+----------------+
| titel | varchar(200) | YES | | NULL | |
| interpret | varchar(200) | YES | | NULL | |
| jahr | int(11) | YES | | NULL | |
| id | bigint(20) unsigned | NO | PRI | NULL | auto_increment |
+-----------+---------------------+------+-----+---------+----------------+
4 rows in set檢視建表語句
mysql> show create table cds;
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| cds | CREATE TABLE `cds` (
`titel` varchar(200) COLLATE latin1_general_ci DEFAULT NULL,
`interpret` varchar(200) COLLATE latin1_general_ci DEFAULT NULL,
`jahr` int(11) DEFAULT NULL,
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=7 DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set查看錶的詳細資訊
mysql> show table status like 'cds';
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Create_options | Comment |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+
| cds | MyISAM | 10 | Dynamic | 3 | 49 | 176 | 281474976710655 | 2048 | 28 | 7 | 2005-10-25 15:47:49 | 2012-04-16 23:30:18 | NULL | latin1_general_ci | NULL | | |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+
1 row in set修改資料庫引擎
mysql> alter table cds engine=InnoDB;
Query OK, 3 rows affected
Records: 3 Duplicates: 0 Warnings: 0再次查看錶的詳細資訊
mysql> show table status like 'cds';
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-------------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Create_options | Comment |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-------------------+----------+----------------+---------+
| cds | InnoDB | 10 | Compact | 3 | 5461 | 16384 | 0 | 0 | 6291456 | 7 | 2012-04-16 23:30:18 | NULL | NULL | latin1_general_ci | NULL | | |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-------------------+----------+----------------+---------+