/// <summary>
/// 尝试将查询列表达式解析为查询列信息。
/// </summary>
/// <param name="table">表达式所属表</param>
/// <param name="expression">表达式</param>
/// <param name="selectColumn">返回查询列信息</param>
/// <returns>返回是否解析成功</returns>
public static bool TryParse(ITable table, string expression, out SelectColumn selectColumn)
{
selectColumn = null;
if (string.IsNullOrEmpty(expression))
{
return(false);
}
var expressions = expression.Split(separator, StringSplitOptions.RemoveEmptyEntries);
if (expressions.Length == 3 && "AS".Equals(expressions[1], StringComparison.InvariantCultureIgnoreCase))
{
selectColumn = new SelectColumn(new Column(table, expressions[0]), expressions[2]);
}
else if (expressions.Length == 2)
{
selectColumn = new SelectColumn(new Column(table, expressions[0]), expressions[1]);
}
else if (expressions.Length == 1)
{
selectColumn = new SelectColumn(new Column(table, expressions[0]));
}
return(true);
}
/// <summary>
/// 向后拼接 Select 列。
/// </summary>
/// <param name="selectColumn">Select 列信息</param>
protected virtual void BuildSelectColumn(SelectColumn selectColumn)
{
BuildColumn(selectColumn.Column);
if (!string.IsNullOrEmpty(selectColumn.Alias))
{
BuildCode(Code_Space);
BuildName(selectColumn.Alias);
}
}