Databases – Unit 3 & 4

 SQL is not restricted to a specific database, however in class we will be looking at the two major database programmes in use  Access – basic database, usable for academic purposes and basic data purposes  SQL Server – industry recognised database, more adaptable, more ‘in depth’

 Made up of US English based ‘key words’  US? US spelling of words is used throughout programming languages due to their origins:  Colour is coded as color (feel free to twitch)

 ADO.Net provides a ‘namespace’ for all possible database connections  System.Data.OleDb  System.Data.SqlClient  Each namespace contains all the functions you will need to manipulate the database and data inside it Access database SQL Server database

 ADO has different versions as it has developed  In version 2.1 more objects were released, ADOX is essentially: ADO eXtrensions  In ADOX all objects use Generalisation to define objects (remember the essays?)

 Dataset  Dataset – stores all data held in ‘cache’  DataAdapter  DataAdapter – represents a bridge between the Dataset and Database holding the: ▪ Connection String ▪ SQL Commands  ConnectionDatasource  Connection – the address of your Datasource (aka database)

 Before you can create any functional SQL your application must be able to connect to your database.  All database connections are called a ‘connection string’  These can be set as global variables or ‘per page’ connections may also be set

public void ConnectToAccess() { System.Data.OleDb.OleDbConnection conn = new System.Data.OleDb.OleDbConnection(); conn.ConnectionString source= C:\Documents and Settings\username\" Documents\AccessFile.mdb"; try { conn.Open(); } catch (Exception ex) { MessageBox.Show("Failed to connect to data source"); } finally { conn.Close(); } } Call an instance of ADO.Net namespace Create the ‘string’ address for your database Try Catch Statement

 Why create a table?  Temporary tables may be created, filled and deleted  Why? Memory Management – A large update is quicker than many small updates

try { conn.Open(); string strTemp = " [FirstName] Text, [LastName] Text "; OleDbCommand myCommand = new OleDbCommand(); myCommand.Connection = conn; myCommand.CommandText = "CREATE TABLE tbl_People(" + strTemp + ")"; myCommand.ExecuteNonQuery(); }

try { conn.Open(); string strTemp = " [FirstName] = " + txtFname.text + ", [LastName] = " + txtLname.Text; OleDbCommand myCommand = new OleDbCommand(); myCommand.Connection = conn; myCommand.CommandText = “INSERT INTO tbl_People(" + strTemp + ")"; myCommand.ExecuteNonQuery(); }

 The Datagrid is a massively useful tool for showing multiple records of data  Using a simple statement records can be shown as a read only table or an editable form

private void Form1_Load(object sender, System.EventArgs e) { Try { OleDbDataAdapter da = new OleDbDataAdapter("SELECT * FROM Student","Provider=Microsoft.JET.OLEDB.4.0;data source=C:\\mcb.mdb" ); DataSet ds = new DataSet(); da.Fill(ds, “Fname"); dataGrid1.DataSource = ds.Tables[“FName"].DefaultView ; } catch (Exception ex) { MessageBox.Show("Failed to connect to data source"); } finally { conn.Close(); } }

 Create yourself a set of revision notes for the SQL code used here. This should include:  A Table of Keywords and their uses  An explanation of ADO  An explanation of connection strings  An explanation of a dataset