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);
}
