Special considerations

Connect to TYPO3's own database

You can also connect to the database of your current TYPO3 installation. This might be useful to migrate data from one table format to another. You could for example migrate data from tt_news to tx_news_domain_model_news:

EXT:my_extension/Configuration/TCA/Overrides/tx_news_domain_model_news.php

$GLOBALS['TCA']['tx_news_domain_model_news'] = array_replace_recursive($GLOBALS['TCA']['tx_news_domain_model_news'],
[
   'external' => [
      'general' => [
         0 => [
            'connector' => 'sql',
            'parameters' => [
               'driver' => $GLOBALS['TYPO3_CONF_VARS']['DB']['Connections']['Default']['driver'],
               'server' => $GLOBALS['TYPO3_CONF_VARS']['DB']['Connections']['Default']['host'],
               'user' => $GLOBALS['TYPO3_CONF_VARS']['DB']['Connections']['Default']['user'],
               'password' => $GLOBALS['TYPO3_CONF_VARS']['DB']['Connections']['Default']['password'],
               'database' => $GLOBALS['TYPO3_CONF_VARS']['DB']['Connections']['Default']['dbname'],
               'query' => 'SELECT * FROM tt_news LIMIT 5'
            ],
            'data' => 'array',
            'referenceUid' => 'import_id',
            'priority' => 5000,
            'description' => 'News import from own database'
         ]
      ]
   ],
   'columns' => [
      // ...
   ],
]);