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);
}
/// <summary>
/// Visit a parse tree produced by <see cref="SelectSQLParser.column"/>.
/// <para>
/// The default implementation returns the result of calling <see cref="AbstractParseTreeVisitor{Result}.VisitChildren(IRuleNode)"/>
/// on <paramref name="context"/>.
/// </para>
/// </summary>
/// <param name="context">The parse tree.</param>
/// <return>The visitor result.</return>
public virtual Result VisitColumn([NotNull] SelectSQLParser.ColumnContext context)
{
return(VisitChildren(context));
}
/// <summary>
/// Exit a parse tree produced by <see cref="SelectSQLParser.column"/>.
/// <para>The default implementation does nothing.</para>
/// </summary>
/// <param name="context">The parse tree.</param>
public virtual void ExitColumn([NotNull] SelectSQLParser.ColumnContext context)
{
}
