public override void EnterColumn(SelectSQLParser.ColumnContext context)
{
Column column = new Column();
if (context.columnExpression().IsEmpty) //不存在列表达式
throw new MissingColumnExpressionException();
var functionalColumn = context.columnExpression().functionableColumn();
var columnName = context.columnExpression().columnName();
if (functionalColumn!=null&&!functionalColumn.IsEmpty)
{
column.Expression = new ColumnExpression(ExpressionType.Function);
column.Expression.Function = new FunctionDescription();
}
else if (columnName!=null&&!columnName.IsEmpty)
{
column.Expression = new ColumnExpression(ExpressionType.ColumnName);
column.Expression.ColumnName = columnName.GetText();
}
else
{
throw new MissingColumnExpressionException();
}
if (context.AS() != null) //存在别名
{
columnName = context.columnName();
if (columnName.IsEmpty) //语法错误
throw new MissingColumnAliasException();
column.HasAlias = true;
column.Alias = columnName.GetText();
}
this.SelectStmt.Columns.Add(column);
}
public override void EnterOrderByStmt(SelectSQLParser.OrderByStmtContext context)
{
var orderBy = new OrderByCondition();
var expression = context.columnExpression();
if (expression == null || expression.IsEmpty)
throw new MissingOrderByException();
orderBy.Expression = expression.GetText();
if (string.IsNullOrEmpty(orderBy.Expression))
throw new MissingOrderByException();
orderBy.Direction = OrderByDirection.DESC;
var direction = context.orderByDirection();
if (direction == null || direction.IsEmpty)
orderBy.Direction = OrderByDirection.ASC;
else if(direction.GetText().Equals("asc", StringComparison.OrdinalIgnoreCase))
orderBy.Direction = OrderByDirection.ASC;
this.SelectStmt.OrderBy.Add(orderBy);
}
