code: function (table) {
              var o = this.__opts;
              if (o.sql) {
                  return this.mergeOptions();
              }
              var h = {};
              array.intersect(Object.keys(o), this._static.QUALIFY_KEYS).forEach(function (k) {
                  h[k] = this._qualifiedExpression(o[k], table);
              }, this);
              if (!o.select || isEmpty(o.select)) {
                  h.select = [new ColumnAll(table)];
              }
              return this.mergeOptions(h);
          }
docs: Return a copy of the dataset with unqualified identifiers in the
  SELECT, WHERE, GROUP, HAVING, and ORDER clauses qualified by the
  given table. If no columns are currently selected, select all
  columns of the given table.
  
  @example
  DB.from("items").filter({id : 1}).qualifyTo("i");
  //=> SELECT i.* FROM items WHERE (i.id = 1)
  
  @param {String} table the name to qualify identifier to.
  
  @return {patio.Dataset} a cloned dataset with unqualified identifiers qualified.