How do I catch MySQL errors in a try catch block? - mysql

Question

I am trying to execute a query on a MySQL database. I've put the execute command in a try catch block, but It still throws an exception when the query fails. How do I prevent this and simply catch the error?
Dim db_connection As String = my_connection_string
Dim MyConn As OdbcConnection
MyConn = New OdbcConnection(db_connection)
Dim MyCommand As New OdbcCommand()
Dim myReader As OdbcDataReader = Nothing
MyCommand.Connection = MyConn
MyConn.Open()
query = "Alter table Table1 ADD COLUMN `col_2` VARCHAR(50) AFTER `col_1`"
MyCommand.CommandText = query
try
myReader = MyCommand.ExecuteReader()
catch ex as Exception
output(ex.tostring)
end try
myReader.Close()
If the column already exists, it throws an error but if it does not, then everything is fine and the query gets executed and the program go on.

Answer 1

If you are going to catch an exception, you should catch the whole code of the query because, the connection can fail as well for instance.
Dim db_connection As String = my_connection_string
Dim MyConn As OdbcConnection
Dim MyCommand As New OdbcCommand()
try
MyConn = New OdbcConnection(db_connection)
MyCommand.Connection = MyConn
MyConn.Open()
query = "Alter table Table1 ADD COLUMN `col_2` VARCHAR(50) AFTER `col_1`"
MyCommand.CommandText = query
MyCommand.ExecuteNonQuery()
catch ex as Exception
output(ex.tostring)
end try
EDIT:
Try
Using connection As New OdbcConnection(my_connection_string)
query = "Alter table Table1 ADD COLUMN `col_2` VARCHAR(50) AFTER `col_1`"
Using command As New OdbcCommand(query, connection)
connection.Open()
command.ExecuteNonQuery()
End Using
End Using
Catch ex As Exception
Console.WriteLine(ex.Message)
End Try
EDIT
Try
'code here
Catch exception As OdbcException
Console.WriteLine(exception.Message)
Catch ex As Exception
Console.WriteLine(ex.Message)
End Try