I'm working with the migrate module for the first time and I've worked with the db_select api a little bit, but I'm running into an error.

I'm trying to convert some old labels into a drupal taxonomy. When I browse to the /admin/content/migrate page, it does my query correctly and shows the right number of rows that should be migrated. However, when I actually try to run the import, I get this error:

Migration failed with source plugin exception: SQLSTATE[23000]: Integrity constraint violation: 1052 Column 'labelId' in on clause is ambiguous

Here is the code I have in my LabelMigration class:

$this->map = new MigrateSQLMap($this->machineName,

        'labelId' => array('type' => 'int', 'not null' => TRUE)
$query = db_select('migrate_account_label', 'l')
         ->fields('l', array('labelId', 'label'))

$query->leftJoin('migrate_asset_labels_membership', 'lm', 'l.labelId = lm.labelId');
$query->leftJoin('migrate_asset', 'a', 'lm.assetId = a.assetId');
$query->addExpression('count(*)', 'num');
$query->condition('a.type', 'B');

$this->source = new MigrateSourceSQL($query);

// Set up our destination - terms in the vocabulary
$this->destination = new MigrateDestinationTerm('article_labels');

$this->addFieldMapping('name', 'label');

If I remove the leftJoin() calls then obviously the error about the on statement goes away, but I don't understand how labelId is ambiguous because I'm always referencing it with a table alias.

Any ideas where this error is coming from? Is it coming from the MigrateSQLMap at the top? If so, how can I reference that labelId with an alias to make it non-ambiguous? I tried making it l.labelId, but that didn't work.

2 Answers 2


Figured it out!

When defining the field in the MigrateSQLMap I can set a table alias for the field:

$this->map = new MigrateSQLMap($this->machineName,
        'labelId' => array(
            'type' => 'int',
            'not null' => TRUE,
            'alias' => 'l', // it's the letter small case "L", not the digit 1

The 'alias' => 'l' makes the labelId become l.labelId in the queries.

  • Thanks. Had the same problem. You should mark your answer as correct.
    – Perisdr
    Dec 5, 2012 at 15:23
  • Same problem... and solution works perfectly. I've spent way too many hours on this one! Thank you for posting the fix.
    – sea26.2
    Jan 12, 2013 at 21:21
  • You deserve a medal for that tid bit.
    – doublejosh
    Oct 1, 2014 at 20:01

I thought that he was setting alias to 1 (ie, boolean true), but there's a reason it's a string - that is the actual alias, so if you're alias is n, 'alias' => 'n'. That actually cost me about 1/2 hr.

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