我需要选择最小的自动递增编号,然后选择ID号以供选择学生信息时参考。这是我得到的:
strSQL = "SELECT min(number) from main_queue "
cmd = New MySqlCommand(strSQL, CONNECTION)
dr = cmd.ExecuteReader
If dr.HasRows Then
dr.Read()
Dim min As Integer
min = dr("min(number)")
strSQL = "SELECT idno_ from main_queue where number='" + min + "'"
cmd = New MySqlCommand(strSQL, CONNECTION)
If dr.HasRows Then
dr.Read()
Dim idnum As Integer
idnum = dr("idno_")
strSQL = "SELECT * from student_records where number='" + idnum + "'"
cmd = New MySqlCommand(strSQL, CONNECTION)
If dr.HasRows Then
dr.Read()
mon_name.Text = dr("name_")
mon_IDno.Text = dr("IDno")
End If
End If
End If
我收到“从字符串“”到类型“ Double”的转换无效。” 在我使用最小自动递增数字作为参考来选择ID号的行上出现错误。
也许我不能正确理解您的数据库架构,但是似乎您可以在一个查询中将其全部写入
Dim strSQL = "SELECT * FROM student_records " & _
"where idNO = " & _
"(SELECT idno_ from main_queue where number= " & _
"(SELECT min(number) from main_queue))"
cmd = New MySqlCommand(strSQL, CONNECTION)
If dr.Read() Then
mon_name.Text = dr("name_")
mon_IDno.Text = dr("IDno")
End If
本文收集自互联网,转载请注明来源。
如有侵权,请联系[email protected] 删除。
我来说两句