add comment to migrate examples.

Hello, my name is Dan and I'm running a migration for a law firm into Drupal 6.20. I keep running into the same issue, though, and I was wondering if anyone could take a glance and maybe help me out.

I think the problem resides in how I'm defining the schema for the key on the source db (MySQL, local but in a separate db from Drupal, which may also be causing problems), but I haven't found much documentation as to how to define that schema, particularly in cases where the key is a varchar(50). If anyone could help me find docs on that, regardless of helping me solve my specific issue, I'd be very grateful.

Anyways, here's my module. This is the .inc I have:

class PAMigration extends Migration {
  public function __construct() {
    parent::__construct();
    $this->description = t('Migrates \'Groups\' from the old data and makes them into new Practice Area nodes');
    $query = db_select('acuweb_mmweb.groups', 'g')
             ->fields('g', array('UID', 'PracticeGroup', 'Description'));
    $this->source = new MigrateSourceSQL($query);
    $this->destination = new MigrateDestinationNode('practices');
    $this->map = new MigrateSQLMap($this->machineName,
        array(
          'UID' => array(
		'type' => 'varchar',
		'length'=> 50,	
		'not null' => TRUE,
           )
        ),
        MigrateDestinationNode::getKeySchema()
      );
    
    // mapped source fields
    $this->addFieldMapping('title', 'PracticeGroup')
         ->description(t('Mapping Practice Group name to the title of the node.'));
    $this->addFieldMapping('body', 'Description')
         ->description(t('Mapping Practice Group description to the body of the node.'));
  }
}

And the errors I'm recieving when I run drush migrate-import PA:

dan@dan-VirtualBox:/var/www/sites/all/modules/migrate$ drush migrate-import PA
Undefined property: stdClass::$UID
File /var/www/sites/all/modules/migrate/plugins/sources/sql.inc, line 354(file: /var/www/sites/all/modules/migrate/plugins/sources/sql.inc, line 354)PHP Fatal error:  Uncaught exception 'PDOException' with message 'SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'sourceid1' cannot be null' in /var/www/sites/all/modules/dbtng/database/database.inc:1964
Stack trace:
#0 /var/www/sites/all/modules/dbtng/database/database.inc(1964): PDOStatement->execute(Array)
#1 /var/www/sites/all/modules/dbtng/database/database.inc(562): DatabaseStatementBase->execute(Array, Array)
#2 /var/www/sites/all/modules/dbtng/database/mysql/query.inc(37): DatabaseConnection->query('INSERT INTO {mi...', Array, Array)
#3 /var/www/sites/all/modules/migrate/plugins/sources/sqlmap.inc(376): InsertQuery_mysql->execute()
#4 /var/www/sites/all/modules/migrate/includes/migration.inc(870): MigrateSQLMap->saveMessage(Array, 'SQLSTATE[23000]...', 1)
#5 /var/www/sites/all/modules/migrate/includes/migration.inc(465): Migration->saveMessage('SQLSTATE[23000]...')
#6 /var/www/sites/all/modules/migrate/includes/base.inc(798): Migration->import()
#7 /var/www/sites/all/modules/migrate/migrate.drush.inc(673) in /var/www/sites/all/modules/dbtng/database/database.inc on line 1964
Drush command terminated abnormally due to an unrecoverable error.                                                          [error]
Error: Uncaught exception 'PDOException' with message 'SQLSTATE[23000]: Integrity constraint violation: 1048 Column
'sourceid1' cannot be null' in /var/www/sites/all/modules/dbtng/database/database.inc:1964
Stack trace:
#0 /var/www/sites/all/modules/dbtng/database/database.inc(1964): PDOStatement->execute(Array)
#1 /var/www/sites/all/modules/dbtng/database/database.inc(562): DatabaseStatementBase->execute(Array, Array)
#2 /var/www/sites/all/modules/dbtng/database/mysql/query.inc(37): DatabaseConnection->query('INSERT INTO {mi...', Array,
Array)
#3 /var/www/sites/all/modules/migrate/plugins/sources/sqlmap.inc(376): InsertQuery_mysql->execute()
#4 /var/www/sites/all/modules/migrate/includes/migration.inc(870): MigrateSQLMap->saveMessage(Array, 'SQLSTATE[23000]...',
1)
#5 /var/www/sites/all/modules/migrate/includes/migration.inc(465): Migration->saveMessage('SQLSTATE[23000]...')
#6 /var/www/sites/all/modules/migrate/includes/base.inc(798): Migration->import()
#7 /var/www/sites/all/modules/migrate/migrate.drush.inc(673) in /var/www/sites/all/modules/dbtng/database/database.inc, line
1964

Any help or at least point me in the right direction would be very helpful. Requests for further information will be honored if I can. Thank you in advance!