Possible to have multiple SqlCommand? - sql

Question

Dim conn As New SqlConnection("Database=Clinic_Management_System;Data Source=.\SQLExpress;Integrated Security=True;AttachDBFilename=|DataDirectory|Clinic Management System.mdf")
Dim cmd As SqlCommand
Dim dr As SqlDataReader
conn.Open()
cmd = New SqlCommand("INSERT INTO record([PatientID],[Prescription],[VisitDate]) Values ('" & PatientIDTextBox.Text & "','" & txtPrescription.Text & "',GetDate()) ", conn)
cmd.ExecuteNonQuery()
For cn As Integer = 0 To DataGridView1.RowCount - 1
cmd = New SqlCommand("INSERT INTO record_item([RecordID],[ItemID],[Amount]) Values ( (SELECT MAX(RecordID) FROM record)," & DataGridView1.Rows(cn).Cells(0).Value & "," & DataGridView1.Rows(cn).Cells(2).Value & ")", conn)
cmd.ExecuteNonQuery()
Next
conn.Close()
Is this possible to run 2 SqlCommand together??
Because after executed somehow the 2nd inside the loop did not execute or insert data.

Answer 1

You don't have 2 SqlCommands.
You have 1 SqlCommand, called cmd, which is executed multiple times.
It is fine to do something like this, however I would have 1 SqlCommand for your INSERT INTO record, and 1 for your INSERT INTO record_item. I think this makes it much easier to understand when looking back at the code at a later date.
Either way, using a SqlCommand like this should not prevent it from executing, therefore I believe there is another issue with your scripting.
I've adapted your code so that it is split into 2 seperate SqlCommand objects, and the queries have been parameterized to prevent SQL Injection:
Dim conn As New SqlConnection("Database=Clinic_Management_System;Data Source=.\SQLExpress;Integrated Security=True;AttachDBFilename=|DataDirectory|Clinic Management System.mdf")
Dim cmdRecord As New SqlCommand("INSERT INTO record ([PatientID],[Prescription],[VisitDate]) Values (#PatientID, #Prescription, GETDATE())", conn)
cmdRecord.Parameters.Add("#PatientID", SqlDbType.Int).Value = PatientIDTextBox.Text
cmdRecord.Parameters.Add("#Prescription", SqlDbType.NVarChar).Value = txtPrescription.Text
Dim cmdRecordItem As New SqlCommand("INSERT INTO record_item([RecordID],[ItemID],[Amount]) Values ( (SELECT MAX(RecordID) FROM record),#ItemID,#AmountID)", conn)
cmdRecordItem.Parameters.Add("#ItemID", SqlDbType.Int)
cmdRecordItem.Parameters.Add("#Amount", SqlDbType.Decimal)
Dim dr As SqlDataReader
conn.Open()
cmdRecord.ExecuteNonQuery()
For cn As Integer = 0 To DataGridView1.RowCount - 1
cmdRecordItem.Parameters("#ItemID").Value = DataGridView1.Rows(cn).Cells(0).Value
cmdRecordItem.Parameters("#Amount").Value = DataGridView1.Rows(cn).Cells(2).Value
cmdRecordItem.ExecuteNonQuery()
Next
conn.Close()

Answer 2

One command can only be used once.
If you want to use more than one command, declare a new cmd as
Dim cmd2 as SqlCommand

Answer 3

In order to ensure that either all statements complete successfully or that none do, you need to wrap your commands in a transaction.
Using parameters for the commands will also make the code more understandable and safer and you should use using statements where possible.
Also, performing the Select max recordid is a very bad idea (if you have multiple users), but I'll leave that for another time:
Using conn As New SqlConnection("Database=Clinic_Management_System;Data Source=.\SQLExpress;Integrated Security=True;AttachDBFilename=|DataDirectory|Clinic Management System.mdf")
Dim cmdRecord As SqlCommand
Dim cmdRecordItem As SqlCommand
Dim oTran As SqlTransaction = Nothing
conn.Open()
Try
cmdRecord = New SqlCommand("INSERT INTO record([PatientID],[Prescription],[VisitDate]) Values (#PatientID, #Prescription, GetDate())", conn)
cmdRecord.Parameters.AddWithValue("#PatientID", PatientIDTextBox.Text)
cmdRecord.Parameters.AddWithValue("#Prescription", txtPrescription.Text)
cmdRecordItem = New SqlCommand("INSERT INTO record_item([RecordID],[ItemID],[Amount]) SELECT ISNULL(MAX(RecordID), 0), #ItemID, #Amount FROM record", conn)
cmdRecordItem.Parameters.Add("#ItemId")
cmdRecordItem.Parameters.Add("#Amount")
oTran = conn.BeginTransaction
cmdRecord.ExecuteNonQuery()
For Each oRow As DataGridViewRow In DataGridView1
cmdRecordItem.Parameters("#ItemId").Value = oRow.Cells(0).Value
cmdRecordItem.Parameters("#Amount").Value = oRow.Cells(2).Value
cmdRecordItem.ExecuteNonQuery()
Next
oTran.Commit()
Catch
If oTran IsNot Nothing Then
oTran.Rollback()
End If
Throw
Finally
conn.Close()
End Try
End Using