为什么mysql没有innodb引擘?

用show engines\G;命令发现
*************************** 1. row ***************************
      Engine: MyISAM
    Support: DEFAULT
    Comment: Default engine as of MySQL 3.23 with great performance
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 2. row ***************************
      Engine: MRG_MYISAM
    Support: YES
    Comment: Collection of identical MyISAM tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 3. row ***************************
      Engine: BLACKHOLE
    Support: YES
    Comment: /dev/null storage engine (anything you write to it disappears)
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 4. row ***************************
      Engine: CSV
    Support: YES
    Comment: CSV storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 5. row ***************************
      Engine: MEMORY
    Support: YES