如何从日期为最后一天的表中选择多列？

Posted 2023-05-07

【中文标题】如何从日期为最后一天的表中选择多列？

【英文标题】：How can I select multi-column from table where date is last day?

【发布时间】：2015-05-02 06:15:02

【问题描述】：

我正在尝试从表中选择日期小于今天的字段。

connect.Open();
command.Connection = connect;
today = DateTime.Today.ToString("dd/MM/yyyy");
string query = "select attendance as [Attend], Emp_UserId as ID, 'Date_ofday' as [Today Date] , Emp_UserName as Name ,Delay_Hours as [Delay Hours] from Attendance where Date_ofday > '"+ DateTime.Parse(today) + "'  ";
command.CommandText = query;
OleDbDataAdapter da1 = new OleDbDataAdapter(command);
DataTable dt1 = new System.Data.DataTable();
da1.Fill(dt1);
dataGridView1.DataSource = dt1;

这会产生data type miss 或missing operator 错误，使用 Access DB。

【问题讨论】：

我给出了答案，但我不明白您使用的是什么数据库。是 mysql（标签）还是 MS Access？

【参考方案1】：

您正在将 DateTime 转换为字符串，然后在下一行将其解析回 DateTime，这没有意义。我认为你应该使用参数，看看是否可行，我不使用MySql：

connect.Open();
command.Connection = connect;
todday = DateTime.Today.ToString("dd/MM/yyyy");
string query = "select attendance as [Attend], Emp_UserId as ID, 'Date_ofday' as [Today Date] , Emp_UserName as Name ,Delay_Hours as [Delay Hours] from Attendance where Date_ofday > @Today";
command.CommandText = query;
OleDbDataAdapter da1 = new OleDbDataAdapter(command);
DataTable dt1 = new System.Data.DataTable();
da1.SelectCommand.Parameters.AddWithValue("@Today", DateTime.Today);
da1.Fill(dt1);
dataGridView1.DataSource = dt1;

如果您使用的是 MS Access，则查询变为：

string query = "select attendance as [Attend], Emp_UserId as ID, 'Date_ofday' as [Today Date] , Emp_UserName as Name ,Delay_Hours as [Delay Hours] from Attendance where Date_ofday > ?";

【讨论】：

我用的是 Access 数据库，非常感谢，效果很好