public SelectExpression(TargetExpression columns, FromExpression table)
 {
     this.Target = columns;
     this.From   = table;
     this.Where  = new WhereExpression(null);
 }
 public SelectExpression(TargetExpression columns, FromExpression table, WhereExpression where)
 {
     this.Target = columns;
     this.From   = table;
     this.Where  = where;
 }