In which file should I write db_add_field function

Question

I am writing a module for which I have to add a field to my database. So I need to use db_add_filed function, So in which file I should use this function? I mean should it be in .module file or .inc file?

Answer 1

I think you should write your code for adding new field in DB in your .module file. Here is the code for you :

function xyz_schema_alter(&$schema) {
  // Add field to existing schema.
  $schema['node']['fields']['show_in_inbox'] = array(
    'type' => 'int',
    'length' => '4',
    'default' => '1',
    'not null' => TRUE,
    'unsigned' => TRUE,  
    'description' => 'Field added by xyz module',
  ); 
}

function xyz_enable(){
    if (!db_field_exists('node', 'show_in_inbox')) {
        $schema = drupal_get_schema('node');
        db_add_field('node', 'show_in_inbox', $schema['fields']['show_in_inbox']);
    }
}

The new field will be added in your existing database on enabling this module.

Answer 2

If the field is static, I should think you want to create any db tables as part of the install (https://api.drupal.org/api/drupal/modules%21system%21system.api.php/function/hook_install/7). Just don't forget to remove it as part of an uninstall.

If it's being created dynamically, then the point at which it needs to be created should dictate where and when to place the code.