1千万(InnoDB)
select *        21秒
select id=xxx   0.026秒
count(id)       15.71秒(第一次16.71,第二次0秒，插入一条后16.476秒)
count(username) 16.956秒
avg(id)         18.41秒

1千万(Myisam)
select *        8.389秒
select id=xxx   0秒
count(*)        0秒
count(username) 1.643秒
avg(id)         3.793秒

myisam-->innodb 52.200秒

| Feature                      | MyISAM       | InnoDB       |
| B-tree indexes               | Yes          | Yes          |
| Backup/point-in-time 恢复    | Yes          | Yes          |
| Cluster database support     | No           | No           |
| Clustered indexes            | No           | Yes          |
| Compressed data              | Yes (note 2) | Yes          |
| Data caches                  | No           | Yes          |
| Encrypted data (note 3)      | Yes          | Yes          |
| Foreign key support          | No           | Yes          |
| Full-text search indexes     | Yes          | Yes (note 5) |
| Geospatial data type support | Yes          | Yes          |
| Geospatial indexing support  | Yes          | Yes (note 6) |
| Hash indexes                 | No           | No (note 7)  |
| Index caches                 | Yes          | Yes          |
| Locking granularity          | Table        | Row          |
| MVCC                         | No           | Yes          |
| Replication support (note 1) | Yes          | Yes          |
| Storage limits               | 256TB        | 64TB         |
| T-tree indexes               | No           | No           |
| Transactions                 | No           | Yes          |
| Update statistics for data dictionary YesYes

#原文
MyISAM: These tables have a small footprint. Table-level locking limits the performance in read/write workloads, 
so it is often used in read-only or read-mostly workloads in Web and data warehousing configurations.
#意思
MyISAM应用范围比较小。它是表级锁，对并发读写有限制。适合只读或者大部分是读的web应用或者配置性的数据仓库。