using hook_query_alter with fieldcondition()

Question

I want to use hook_query_alter to alter a query constructed by a module. This is the code I use:

function MYMODULE_query_alter($query) {
  if ($query->hasTag('agent')) {
    $query->fieldCondition('field_area', 'tid', 10, '=');
  }
}

The code above gives a 500 error: Call to undefined method SelectQuery::fieldCondition()

What is the proper way to add a field condition to the query?

Answer 1

This was solved using the $query->innerJoin()

Answer 2

To use condition in query simply use:

$query->condition('field_area', 'tid', 10, '=');