There are 10 rows in primary_student_table.
When I execute the following code, the result was -1.
Dim count As Int16
con.Open()
query = "SELECT COUNT(roll) AS rollcount FROM primary_student_table WHERE admityear = 2011 AND batch = 1 "
cmd = New SqlCommand(query, con)
count = cmd.ExecuteNonQuery
MsgBox(count)
con.Close()
What's the problem in the above code?
You should be using ExecuteScalar() rather than ExecuteNonQuery() because you are fetching a value.
count = Convert.ToInt16(cmd.ExecuteScalar())
MsgBox(count.ToString())
For proper coding
using statement for proper object disposaltry-catch block to properly handle exceptionsExample Code:
Dim connStr As String = "connection string here"
Dim query As String = "SELECT COUNT(roll) AS rollcount FROM primary_student_table WHERE admityear = 2011 AND batch = 1"
Using conn As New SqlConnection(connStr)
Using cmd As New SqlCommand()
With cmd
.Connection = conn
.CommandText = query
.CommandType = CommandType.Text
End With
Try
conn.Open()
Dim count As Int16 = Convert.ToInt16(cmd.ExecuteScalar())
MsgBox(count.ToString())
Catch(ex As SqlException)
' put your exception here '
End Try
End Using
End Using
The solution is to replace
count = cmd.ExecuteNonQuery
with
count = cmd.ExecuteScalar
Like Robert Beaubien said in his comments
MysqlConn = New MySqlConnection
MysqlConn.ConnectionString = "server=localhost;userid=root;password=1234;database=dblms"
Dim READER As MySqlDataReader
Try
MysqlConn.Open()
Dim Query As String
Query = "Select * from dblms.accounts"
COMMAND = New MySqlCommand(Query, MysqlConn)
READER = COMMAND.ExecuteReader
Dim count As Integer
count = 0
While READER.Read
count = count + 1
End While
MysqlConn.Close()
Catch ex As MySqlException
MessageBox.Show(ex.Message)
Finally
MysqlConn.Dispose()
End Try
the value in count will be the number of rows in a table :) hope this helped
Disposeoncmdandconafter you've finished using them. 2. Nothing wrong withInt16, but in VB.NET you'd usually refer to that type using the keywordShort. 3. Ideally, you'd callcon.Open()at the latest-possible moment, i.e. right before executing the command; i.e. generally, try to keep connections open for the shortest-possible time.count(*)andcount(row)can produce different results.