Fetch SQL records without going through each row - mysql

Question

Context:
I have around 50 records of names with their fingerprints saved in a database that will be needed for their daily time-in/time-out using a fingerprint scanner.
The code:
Dim conn As New MySqlConnection("...database_details")
Dim cmd As New MySqlCommand
Private Sub FetchRecords(sender As Object, e As IZKFPEngXEvents_OnCaptureEvent) Handles ZkFprint.OnCapture
'fingerprint sample from the scanner, returns a BASE64 format
Dim fp = e.aTemplate
Using conn
conn.Open()
cmd = conn.CreateCommand()
With cmd
.CommandType = CommandType.Text
'fprint stores varchar data type
.CommandText = "SELECT id,name,reg_fprint FROM tbl_emp"
End With
Dim dr as MySqlDataReader = cmd.ExecuteReader()
While dr.Read
'converts the fprint into BASE64
Dim fpFromDB = ZkFprint.DecodeTemplate1(dr.GetValue(1))
'compares fp to fpFromDB; returns true if match otherwise false
Dim result As = ZkFprint.VerFinger(fpFromDB, fp)
If result = True Then
lbName.Text = dr.GetValue(1)
Else
MessageBox.Show("Fingerprint not found")
End If
End While
End Using
End Sub
The problem:
When I scan a finger to time in/out, the MessageBox.Show("Fingerprint not found") line will trigger X-1 times before my lbName.Text changes to the matching record. This is because dr.Read() reads the first row until I find the record.
What I want:
Is there a way for me to get the record without going through each row?
What I tried:
I removed the Else statement, which solved my problem but leads me to another problem: it does not provide any feedback if a finger is not registered.
If result = True Then
lbName.Text = dr.GetValue(1)
End If
EDIT:
Thanks for the inputs, I appreciate it. I also manage to come up with a solution after playing with the code a few times thanks to #Shadow below the commments. I replaced the While Loop with a For Loop and put the data in a DataTable so I can easily go through them. I also used the recordCount as a reference if a record does not exists.
Dim fp = e.aTemplate
Dim dt As New DataTable
Dim recordCount As Integer
Using conn
conn.Open()
cmd = conn.CreateCommand()
With cmd
.CommandType = CommandType.Text
'fprint stores varchar data type
.CommandText = "SELECT id,name,reg_fprint FROM tbl_emp"
End With
Dim da As New MySqlDataAdapter(cmd)
da.Fill(dt)
For recordCount = 0 To dt.Rows.Count - 1
Dim result As = ZkFprint.VerFinger(dt.Rows(recordCount).Item(2).ToString, fp)
If result = True Then
lbName.Text = dt.Rows(recordCount).Item(1).ToString
Exit For
End If
Next
If recordCount = dt.Rows.Count Then
MessageBox.Show("Fingerprint not found")
End If
End Using

Answer 1

You may consider comparing the column fild while converting to base64
Dim conn As New MySqlConnection("...database_details")
Dim cmd As New MySqlCommand
Private Sub FetchRecords(sender As Object, e As IZKFPEngXEvents_OnCaptureEvent) Handles ZkFprint.OnCapture
'fingerprint sample from the scanner returns a BASE64 format
Dim fp = e.aTemplate
Using conn
conn.Open()
cmd = conn.CreateCommand()
With cmd
.CommandType = CommandType.Text
'fprint stores varchar data type
.CommandText = "SELECT id,name,reg_fprint FROM tbl_emp WHERE TO_BASE64(reg_fprint)=#reg_fprint"
.Parameters.Add(New MySqlClient.MySqlParameter("#reg_fprint", fp))
End With
Dim dr as MySqlDataReader = cmd.ExecuteReader()
If dr.Read
lbName.Text = dr.GetValue(1)
lbName.refresh() 'To update label text
Else
MessageBox.Show("Fingerprint not found")
End If
End Using
End Sub
But again you could change this block
If result = True Then
lbName.Text = dr.GetValue(1)
End If
to
If result = True Then
lbName.Text = dr.GetValue(1)
lbName.Refresh() 'Update the label
End If