function hook_schema_alter

Perform alterations to existing database schemas.

When a module modifies the database structure of another module (by changing, adding or removing fields, keys or indexes), it should implement hook_schema_alter() to update the default $schema to take its changes into account.

See hook_schema() for details on the schema definition structure.

Parameters

$schema: Nested array describing the schemas for all modules.

Related topics

File

drupal/modules/system/system.api.php, line 3294

Hooks provided by Drupal core and the System module.

Code

function hook_schema_alter(&$schema) {

  // Add field to existing schema.
  $schema['users']['fields']['timezone_id'] = array(
    'type' => 'int',
    'not null' => TRUE,
    'default' => 0,
    'description' => 'Per-user timezone configuration.',
  );
}