Visual Basic and SQL Server – Deleting Data
In order to delete data in an SQL Server database, the SQL ‘Delete’ statement needs to be used. The following example deletes a record with a specific ‘id’ from the ‘person’ table, which was used in the examples for selecting, inserting and updating data.
Deleting data works in a similar way to the other examples, where a parameterised query is used. Firstly, a connection to the database is established, then the query parameter for the ‘id’ of the record to be deleted is defined as a variable, which is bound in to the following SQL statement. The SQL statement is then executed and a confirmation message is displayed. The declaration and execution of the SQL statement is wrapped in a ‘Try-Catch-Finally’ block to catch any errors that may arise and close the database connection at the end.
' Database connection variable. Dim connect = New SqlConnection( "Server=localhost\MSSQLSERVERDEMO; Database=Demo;" & "User Id=DemoUN; Password=DemoPW") Try ' Connect to database. connect.Open() Catch ex As Exception ' Confirm unsuccessful connection and stop program execution. Console.WriteLine("Database connection unsuccessful.") End End Try Try ' Query parameter. Dim id As Integer = 2 ' Query text. Dim sqlText As String = "DELETE FROM person " & "WHERE id = @id" ' Query text incorporated into SQL command. Dim sqlDelete As New SqlCommand(sqlText, connect) ' Bind the parameter to the query. sqlDelete.Parameters.AddWithValue("@id", id) ' Execute SQL. sqlDelete.ExecuteNonQuery() ' Confirm successful deletion of person information. Console.WriteLine("Person information deleted successfully.") Catch ex As Exception ' Confirm error deleting person information and exit. Console.WriteLine("Error deleting person information.") End Finally ' Close the database connection. connect.Close() End Try
The contents of the ‘person’ table now looks as follows.