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    1. General Information
    2. MySQL Installation
    3. Tutorial Introduction
    4. Database Administration
    5. MySQL Optimisation
    6. MySQL Language Reference
    7. MySQL Table Types
    8. MySQL APIs
    9. Extending MySQL
    494 MySQL Technical Reference for Version 4.0.3 7  MySQL Table Types As of MySQL Version 3.23.6, you can choose between three basic table formats (ISAM, HEAP and MyISAM. Newer MySQL may support additional table type (InnoDB, or BDB), depending on how you compile it. When you create a new table, you can tell MySQL which table type it should use for the table.   MySQL  will  always  create  a  `.frm'   le  to  hold  the  table  and  column  de nitions. Depending on the table type, the index and data will be stored in other les. Note that to use InnoDB tables you have to use at least the innodb_data_file_path startup option.  See Section 7.5.2 [InnoDB start], page 507. The  default  table  type  in  MySQL  is  MyISAM.   If  you  are  trying  to  use  a  table  type  that is not compiled-in or activated, MySQL will instead create a table of type  MyISAM.  This is a very useful feature when you want to copy tables between di erent SQL servers that supports di erent table types (like copying tables to a slave that is optimised for speed by not having transactional tables).  This automatic table changing can however also be very confusing for new MySQL users.  We plan to x this by introducing warnings in MySQL 4.0 and giving a warning when a table type is automatically changed. You can convert tables between di erent types with the ALTER TABLE statement.  See Sec- tion 6.5.4 [ALTER TABLE], page 476. Note that MySQL supports two di erent kinds of tables:  transaction-safe tables (InnoDB and BDB) and not transaction-safe tables (HEAP, ISAM, MERGE, and MyISAM). Advantages of transaction-safe tables (TST):    Safer.  Even if MySQL crashes or you get hardware problems, you can get your data back, either by automatic recovery or from a backup + the transaction log.    You  can  combine  many  statements  and  accept  these  all  in  one  go  with  the  COMMIT command.    You  can  execute  ROLLBACK  to  ignore  your  changes  (if  you  are  not  running  in  auto commit mode).    If an update fails, all your changes will be restored.  (With NTST tables all changes that have taken place are permanent) Advantages of not transaction-safe tables (NTST):    Much faster as there is no transaction overhead.    Will use less disk space as there is no overhead of transactions.    Will use less memory to do updates. You can combine TST and NTST tables in the same statements to get the best of both worlds. 7.1  MyISAM Tables MyISAM  is the default table type in MySQL Version 3.23.  It's based on the  ISAM  code and has a lot of useful extensions.
     

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