为数据表中的计算列定义 DateDiff

发布于 2024-08-28 19:02:49 字数 434 浏览 3 评论 0原文

我有 DateTimeExpired 列，我想创建另一个名为“Expired”的列，该列将根据到期日期显示“是”或“否” - 如果日期已过，则显示“是”。
我写了这个：

DataColumn colExpirationDate = new DataColumn("DateTimeExpired", typeof(DateTime));
DataColumn colExpired = new DataColumn("Expired", typeof(string), "IIF(DateDiff(DateTimeExpired, date())>= 0,'No','Yes')");

但我得到一个异常“表达式包含未定义的函数调用 DateDiff()。”

（请注意，我总是想要获取该行，无论它是否过期）

如何将列的文本设置为正确的形式？

原文

I have the column DateTimeExpired, and I would like to create another column called "Expired" which will show "Yes" or "No" according to the expiration date - "Yes" if the date has already passed.
I wrote this:

DataColumn colExpirationDate = new DataColumn("DateTimeExpired", typeof(DateTime));
DataColumn colExpired = new DataColumn("Expired", typeof(string), "IIF(DateDiff(DateTimeExpired, date())>= 0,'No','Yes')");

But I get an exception "The expression contains undefined function call DateDiff()."

(please note that I always want to get the row, no matter if it's expired or not)

How do I set the column's text to the correct form?

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痴意少年 2024-09-04 19:02:50

正如 MA Hanin 在评论中指出的那样，看起来 DateDiff 不能在数据列表达式。您可以尝试将计算列构建到基础表中（如果您使用的是 MS Sql 或类似的）

编辑：
没有函数可以获取“今天”，但假设您添加的 DataColumn 只会存在几个小时，您可以将今天的日期构建为常量，然后使用比较运算符而不是 DateDiff

尝试这样做：

DataColumn colExpirationDate = new DataColumn("DateTimeExpired", typeof(DateTime));
DataColumn colExpired = new DataColumn("Expired", typeof(string),
    String.Format("IIF(DateTimeExpired > #{0}#,'No','Yes')",
    DateTime.Now.ToString("dd/MMM/yyyy")));

注意这将仅当您的 DataColumn 仅在内存中保留少于一天时才有效。

As M.A Hanin pointed out in his comment, it looks like DateDiff cannot be used in DataColumn Expressions. You could try building the calculated column into the underlying table instead (if you are using MS Sql or similar)

edit:
There is no function to get 'today', but assuming that the DataColumn you are adding will only exist for a few hours, you could build in todays date as a constant, and then use comparison operators instead of DateDiff

Try this:

DataColumn colExpirationDate = new DataColumn("DateTimeExpired", typeof(DateTime));
DataColumn colExpired = new DataColumn("Expired", typeof(string),
    String.Format("IIF(DateTimeExpired > #{0}#,'No','Yes')",
    DateTime.Now.ToString("dd/MMM/yyyy")));

Note this will only work if your DataColumn is only retained in memory for less than a day.

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