How to create table in a custom module in magento

Stuff with mysql4 is outdated for quite a while now. I'd suggest using the following:

Minimum content of config.xml:

<?xml version="1.0"?>
<config>
    <modules>
        <Somnath_Blog>
            <version>1.0.0</version>
        </Somnath_Blog>
    </modules>
    <global>
        <models>
            <blog>
                <class>Somnath_Blog_Model</class>
                <resourceModel>somnath_blog_resource</resourceModel>
            </blog>
            <somnath_blog_resource>
                <class>Somnath_Blog_Model_Resource</class>
                <entities>
                    <blog>
                        <table>blog</table>
                    </blog>
                </entities>
            </somnath_blog_resource>
        </models>
        <resources>
            <somnath_blog_setup>
                <setup>
                    <module>Somnath_Blog</module>
                    <class>Mage_Core_Model_Resource_Setup</class> <!-- optional -->
                </setup>
            </somnath_blog_setup>
        </resources>
    </global>
</config>

Your sql install script in app/code/local/Somnath/Blog/sql/somnath_blog_setup/install-1.0.0.php

/** @var $installer Mage_Core_Model_Resource_Setup */
$installer = $this;

$installer->startSetup();

$table = $installer->getConnection()
    ->newTable($installer->getTable('blog/blog'))
    ->addColumn(
        'blog_id', Varien_Db_Ddl_Table::TYPE_INTEGER, null,
        array(
            'identity' => true,
            'unsigned' => true,
            'nullable' => false,
            'primary'  => true,
        ), 'Unique identifier'
    )
    ->addColumn(
        'title', Varien_Db_Ddl_Table::TYPE_TEXT, 100, array(), 'Blog title'
    )
    ->addColumn(
        'content', Varien_Db_Ddl_Table::TYPE_TEXT, null, array(), 'Blog content'
    )
    ->addColumn(
        'author', Varien_Db_Ddl_Table::TYPE_TEXT, 100, array(), 'Blog author'
    );

if (!$installer->getConnection()->isTableExists($table->getName())) {
    $installer->getConnection()->createTable($table);
}

$installer->endSetup();

And ofcourse you create the basic model / resource models.

Your config.xml has to be in this way.

<?xml version="1.0"?>
<config>
    <modules>
        <[Namespace]_[Module]>
            <version>0.1.0</version>
        </[Namespace]_[Module]>
    </modules>
    <frontend>
        <routers>
            <[module]>
                <use>standard</use>
                <args>
                    <module>[Namespace]_[Module]</module>
                    <frontName>[module]</frontName>
                </args>
            </[module]>
        </routers>
        <layout>
            <updates>
                <[module]>
                    <file>[module].xml</file>
                </[module]>
            </updates>
        </layout>
    </frontend>   
    <global>
        <models>
            <[module]>
                <class>[Namespace]_[Module]_Model</class>
                <resourceModel>[module]_mysql4</resourceModel>
            </[module]>
            <[module]_mysql4>
                <class>[Namespace]_[Module]_Model_Mysql4</class>
                <entities>
                    <[module]>
                        <table>[module]</table>
                    </[module]>
                </entities>
            </[module]_mysql4>
        </models>
        <resources>
            <[module]_setup>
                <setup>
                    <module>[Namespace]_[Module]</module>
                </setup>
                <connection>
                    <use>core_setup</use>
                </connection>
            </[module]_setup>
            <[module]_write>
                <connection>
                    <use>core_write</use>
                </connection>
            </[module]_write>
            <[module]_read>
                <connection>
                    <use>core_read</use>
                </connection>
            </[module]_read>
        </resources>
        <blocks>
            <[module]>
                <class>[Namespace]_[Module]_Block</class>
            </[module]>
        </blocks>
        <helpers>
            <[module]>
                <class>[Namespace]_[Module]_Helper</class>
            </[module]>
        </helpers>
    </global>
</config>

Check that did you extends resource collection or not. If No, then it has to be in this way.

<?php

class <Namespace>_<Module>_Model_Mysql4_<Module>_Collection extends Mage_Core_Model_Mysql4_Collection_Abstract
{
    public function _construct()
    {
        //parent::__construct();
        $this->_init('<module>/<module>');
    }
}

Check this link for more details.

http://www.magentocommerce.com/wiki/5_-_modules_and_development/0_-_module_development_in_magento/custom_module_with_custom_database_table

Create a mysql4-install-0.1.0.php in etc folder. And use the below script to create table in custom module.

<?php
$installer = $this;
$installer->startSetup();
$sql=<<<SQLTEXT
create table tablename(tablename_id int not null auto_increment, name varchar(100), primary key(tablename_id));
    insert into tablename values(1,'tablename1');
    insert into tablename values(2,'tablename2');

SQLTEXT;

$installer->run($sql);

$installer->endSetup();

?>

$installer = $this;

$installer->startSetup();

$installer->run("

DROP TABLE IF EXISTS `{$this->getTable('customer_form_table')}`;
CREATE TABLE `{$this->getTable('customer_form_table')}` (
`log_id` int(11) unsigned NOT NULL auto_increment,
`created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
`admin_id` int(11) unsigned NOT NULL default '0',
`customer_id` int(11) unsigned NOT NULL default '0',
`terms_old` int(11) unsigned NOT NULL default '0',
`terms_new` int(11) unsigned NOT NULL default '0',
`limit_old` DECIMAL(10,5) NOT NULL default '0',
`limit_new` DECIMAL(10,5) NOT NULL default '0',
`available_old` DECIMAL(10,5) unsigned NOT NULL default '0',
`available_new` DECIMAL(10,5) unsigned NOT NULL default '0',
 PRIMARY KEY (`log_id`),
 INDEX (customer_id),
 INDEX (admin_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

 ");

 $installer->endSetup();