ALTER TABLE in Magento setup script without using SQL

Question

Jonathon Day says

\"updates SHOULD NOT be in the form of SQL commands\". I haven\'t come across any DDL or DML statments that cannot be executed

Answer 1

To alter table and add column with a foreign key, I have used this successfully using Magento CE v1.6.1.0 :

// Alter table to add column
$installer->getConnection()

        ->addColumn(
            $installer->getTable('modulekey/model'), 
            'column_name',  
            array(
                'type'      => Varien_Db_Ddl_Table::TYPE_INTEGER,
                'length'    => null,
                'unsigned'  => true,
                'nullable'  => true,
                'comment'   => 'Foreign key'
            )
        );

// Add foreign key constraint
$installer->getConnection()

        ->addForeignKey(
            $installer->getFkName( 
                'modulekey/model',  'column_name',
                'modulekey/foreign_model',  'foreign_column_name'
            ),
            $installer->getTable('modulekey/model'), 
            'column_name',
            $installer->getTable('modulekey/foreign_model'),
            'foreign_column_name',
            Varien_Db_Ddl_Table::ACTION_SET_NULL, 
            Varien_Db_Ddl_Table::ACTION_SET_NULL
        );

Those are methods from Varien_Db_Adapter_Pdo_Mysql.