Sunday, November 30, 2014

Difference between MyISAM and InnoDB.

difference between MyISAM and InnoDB.

The main differences between InnoDB and MyISAM are support for "referential integrity" and "transactions".
If you need the database to enforce foreign key constraints, or you need the database to support then you would choose the InnoDB engine, since these features are absent from the MyISAM engine.
Those are the two biggest differences. Another big difference is concurrency. With MyISAM, a DML statement will obtain an exclusive lock on the table, and while that lock is held, no other session can perform a SELECT or a DML operation on the table.
Those two specific engines you asked about (InnoDB and MyISAM) have different design goals. MySQL also has other storage engines, with their own design goals.
So, in choosing between InnoDB and MyISAM, the first step is in determining if you need the features provided by InnoDB. If not, then MyISAM is up for consideration.
A more detailed discussion of differences is rather impractical (in this forum) absent a more detailed discussion of the problem space... how the application will use the database, how many tables, size of the tables, the transaction load, volumes of select, insert, updates, concurrency requirements, replication features, etc.

MYISAM:
1.    MYISAM supports Table-level Locking
2.    MyISAM designed for need of speed
3.    MyISAM does not support foreign keys hence we call MySQL with MYISAM is DBMS
4.    MyISAM stores its tables, data and indexes in diskspace using separate three different files. (tablename.FRM, tablename.MYD, tablename.MYI)
5.    MYISAM not supports transaction. You cannot commit and rollback with MYISAM. Once you issue a command it’s done.
6.    MYISAM supports fulltext search
7.    You can use MyISAM, if the table is more static with lots of select and less update and delete.

INNODB:
1.    InnoDB supports Row-level Locking
2.    InnoDB designed for maximum performance when processing high volume of data
3.    InnoDB support foreign keys hence we call MySQL with InnoDB is RDBMS
4.    InnoDB stores its tables and indexes in a tablespace
5.    InnoDB supports transaction. You can commit and rollback with InnoDB

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How to convert all tables from MyISAM into InnoDB?

<?php

      // connectivity with your database here first

      //-------------------------------------------------

    $sql = "SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES

        WHERE TABLE_SCHEMA = 'your_database_name'

        AND ENGINE <> 'InnoDB'";

    $rs = mysql_query($sql);

    while($row = mysql_fetch_array($rs))

    {

        $tbl = $row[0];

        $sql = "ALTER TABLE $tbl ENGINE=INNODB";

        mysql_query($sql);

    }

?>



  

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