public DeleteCommand(TableExpression table, Expression where)
     : base(DbExpressionType.Delete, typeof(int))
 {
     this.table = table;
     this.where = where;
 }
 public InsertCommand(TableExpression table, IEnumerable <ColumnAssignment> assignments)
     : base(DbExpressionType.Insert, typeof(int))
 {
     this.table       = table;
     this.assignments = assignments.ToReadOnly();
 }