In Drupal 8, the usage of database operations such as select, update and delete are slightly changed from Drupal 7. The db_query() is deprecated in Drupal 8. To fetch a field we can use :
$query = \Drupal::database()->query('SELECT myfield from my_table where
field1 = :value1 AND field2 = :value2', array(
':value1' => $condition1,
':value2' => $condition2,
)
);
$data = $query->fetchField();Now we can checkout the select, update, and delete operations in Drupal 8. For a field selection use,
$query = \Drupal::database()->select('table_name', 'alias')
->fields('alias', ['field1', field2])
->condition('field3', $condition);
$results = $query->execute();
while ($content = $results->fetchAssoc()) {
// Operations using $content.
}For a single field selection we can use $last_paper_id = $last_paper->fetchField();
For update query execution in Drupal 8, we can use,
$table = 'table_name';
\Drupal::database()->update($table)
->fields(array('field1' => $value1, 'field2' => $value2))
->condition('field3', $condition1)
->condition('field4', $condition2)
->execute();For content deletion,
$query = \Drupal::database()->delete('table_name');
$query->condition('field1', $condition1);
$query->condition('field2', $condition2);
$query->execute();Now checkout other database statements in Drupal 8 from this link!
