/**
 * Find the table alias for a table in a query.
 *
 * @param $query
 *   The query to examine for the alias.
 * @param
 *   $table The table to examine for the alias.
 * @return
 *   The alias if it exists, or the name of the table if it's present but not
 *   aliased, or FALSE if the table is not present.
 */
function project_find_alias($query, $table) {
  // See if {$table} is already in the query.
  $match = array();
  // This regexp handles many cases:
  // - {$table} can be either in FROM or in a JOIN clause
  // - Query might end immediately after {$table}
  // - Might not have a table alias for {$table}
  $pattern = "@.*(FROM|JOIN)\s+\{$table\}\s*(\S+)?@";
  if (preg_match($pattern, $query, $match)) {
    $keywords = '@(ON|INNER|LEFT|RIGHT|WHERE|ORDER|GROUP|HAVING|LIMIT)@';
    if (!isset($match[2]) || preg_match($keywords, $match[2])) {
      // No alias found, just use $table.
      $alias = $table;
    }
    else {
      // Alias found.
      $alias = $match[2];
    }
  }
  else {
    // Table not in query.
    $alias = FALSE;
  }

  return $alias;
}