code: function update (table, columns, values) {
      if (this.typecheck) t.typecheck('update', [table, columns, values]);
      if ('string'===typeof columns) {
          columns = [columns];
          values = [values];
      }
      var result = [];
      for (var i=0; i < columns.length; i++) {
          var value = ('string'===typeof values[i]
              // X\'blob\' \'\\xblob\'
              && values[i].indexOf("X\'") != 0 && values[i].indexOf("\'\\x") != 0)
              ? this.string(values[i]) : values[i];
          result.push(columns[i]+'='+value);
      }
      return ['update',table,'set',result.join()].join(' ');
  }
docs: update tbl set col1=val1,col2=val2 ...