protected override SqlExpression VisitSelect(SelectExpression select)
{
bool saveIsOuterMostSelect = this.isOuterMostSelect;
try
{
this.isOuterMostSelect = false;
select = (SelectExpression)base.VisitSelect(select);
bool hasOrderBy = select.OrderBy != null && select.OrderBy.Count > 0;
bool hasGroupBy = select.GroupBy != null && select.GroupBy.Count > 0;
bool canHaveOrderBy = saveIsOuterMostSelect || select.Take != null || select.Skip != null;
bool canReceiveOrderings = canHaveOrderBy && !hasGroupBy && !select.IsDistinct && !AggregateChecker.HasAggregates(select);
bool canPassOnOrderings = !saveIsOuterMostSelect && !hasGroupBy && !select.IsDistinct;
if (!canReceiveOrderings && !canPassOnOrderings && this.gatheredOrderings != null)
throw new InvalidOperationException("此表达式可能导致排序信息丢失，请尽量把OrderBy，ThenBy之类的调用放到表达式末尾。");
if (hasOrderBy)
{
this.PrependOrderings(select.OrderBy);
}
IEnumerable<OrderByDeclaration> orderings = null;
if(canReceiveOrderings)
{
orderings = this.gatheredOrderings;
}
else if(canHaveOrderBy)
{
orderings = select.OrderBy;
}
ReadOnlyCollection<ColumnDeclaration> columns = select.Columns;
if (this.gatheredOrderings != null)
{
if (canPassOnOrderings)
{
HashSet<TableAlias> existingAliases = DeclaredAliasGatherer.Gather(select.From);
BindResult project = this.RebindOrderings(this.gatheredOrderings, select.TableAlias, existingAliases, select.Columns);
this.gatheredOrderings = null;
this.PrependOrderings(project.Orderings);
columns = project.Columns.ToReadOnly();
}
else
{
this.gatheredOrderings = null;
}
}
return this.UpdateSelect(select, select.TableAlias, columns, select.From, select.Where, orderings, select.GroupBy, select.Skip, select.Take, select.IsDistinct);
}
finally
{
this.isOuterMostSelect = saveIsOuterMostSelect;
}
}
protected override SqlExpression VisitSelect(SelectExpression select)
{
this.aliases.Add(select.TableAlias);
return select;
}
protected override SqlExpression VisitSelect(SelectExpression select)
{
if (this.isOuterMostSelect)
{
this.isOuterMostSelect = false;
this.Visit(select.Where);// ?
this.VisitOrderBy(select.OrderBy);
this.VisitColumnDeclarations(select.Columns);
}
return select;
}
public static bool HasAggregates(SelectExpression expression)
{
AggregateChecker checker = new AggregateChecker();
checker.Visit(expression);
return checker.hasAggregate;
}
protected override SqlExpression VisitSelect(SelectExpression expr)
{
if (expr.Columns == null || expr.Columns.Count == 0 || expr.From == null)
throw new Exception("invalid sql tree!");
this.Write("SELECT ");
if(expr.IsDistinct)
{
this.Write("DISTINCT ");
}
this.VisitColumnDeclarations(expr.Columns);
this.NewLine(Indentation.Same);
this.Write("FROM ");
this.VisitSource(expr.From);
if(expr.Where != null)
{
this.NewLine(Indentation.Same);
this.Write("WHERE ");
this.Visit(expr.Where);
}
if(expr.GroupBy != null && expr.GroupBy.Count != 0)
{
this.NewLine(Indentation.Same);
this.Write("GROUP BY ");
this.VisitExpressionList(expr.GroupBy);
}
if(expr.OrderBy != null && expr.OrderBy.Count != 0)
{
this.NewLine(Indentation.Same);
this.Write("ORDER BY ");
this.VisitOrderBy(expr.OrderBy);
}
if(expr.Skip != null || expr.Take != null)
{
this.NewLine(Indentation.Same);
this.Write(string.Format("LIMIT {0}, {1}", expr.Skip == null ? 0 : expr.Skip.Value, expr.Take == null ? int.MaxValue : expr.Take.Value));
}
return expr;
}
public InExpression(SqlExpression expression, SelectExpression select)
: base(SqlExpressionType.In)
{
this.Expression = expression;
this.Select = select;
}
