code: function _dropColumn(){
      self._visitingAlter = true;
      var table = self._queryNode.table;
      var result=[
        'ALTER TABLE',
        self.visit(table.toNode())
      ];
      var columns='DROP ('+self.visit(alter.nodes[0].nodes[0]);
      for (var i= 1,len=alter.nodes.length; i<len; i++){
        var node=alter.nodes[i];
        assert(node.type=='DROP COLUMN',errMsg);
        columns+=', '+self.visit(node.nodes[0]);
      }
      columns+=')';
      result.push(columns);
      self._visitingAlter = false;
      return result;
    }
docs: Implement our own drop column: PostgreSQL: ALTER TABLE "name" DROP COLUMN "col1", DROP COLUMN "col2" Oracle:  ALTER TABLE "name" DROP ("col1", "col2")