Question

我在测试如何获取最新的数据库条目时遇到了这个错误，方法是选择所需的列，然后指定唯一ID，即由主ID，ID排序的房间号。

这是我的代码：

  Private Sub Form5_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    Conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\patientinfo.accdb"
    Conn.Open()

  Dim statement As String = " SELECT room_number, patient_name,patient_age,date_confinement,type_sickness, type_fluid, bottle_used, drop_rate FROM tblPatientInfo WHERE room_number=1 ORDER BY ID DESC LIMIT 1"
  RetrieveInfos(statement)

  End Sub

  Public Sub RetrieveInfos(ByRef statement As String)
    Dim cmd As OleDbCommand = New OleDbCommand
    With cmd
        .CommandText = statement
        .CommandType = CommandType.Text
        .Connection = Conn
        .ExecuteNonQuery()


        '--read records in access database----------------
        Dim reader As OleDbDataReader = cmd.ExecuteReader
        While reader.Read
            lblName.Text = (reader.GetString(0))
            lblAge.Text = (reader.GetInt32(1).ToString)
            lblDate.Text = (reader.GetDateTime(2).ToString)
            lblSickness.Text = (reader.GetString(3))
            lblFluid.Text = (reader.GetString(4))
            lblBottle.Text = (reader.GetInt32(5).ToString)
            lbldrops.Text = (reader.GetInt32(6).ToString)

        End While
      reader.Close()

    End With
End Sub

任何帮助将不胜感激。谢谢！

Answer 1

“LIMIT 1”条款是可疑的。建议修改查询以使用“SELECT TOP 1 .....”

Dim statement As String = " SELECT TOP 1 room_number, patient_name,patient_age,
                            date_confinement,type_sickness, type_fluid, bottle_used, drop_rate FROM 
                            tblPatientInfo WHERE room_number=1 ORDER BY ID DESC"

（为了清楚起见，查询包含了硬回车）。

Answer 2

limit特定于MySql。

对于Access或SQL Server：

Select top 1 from ...
Order by ...

对于Oracle：

Select *
from
(
    Select ...
    Order by ...
)
Where row_num = 1

OleDbException：ORDER BY子句中的语法错误

2 个答案: