Databases – Unit 3 & 4Databases – 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 databaseSQL 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?)

DatasetDataset – stores all data held in ‘cache’

DataAdapterDataAdapter – represents a bridge between the Dataset and Database holding the:▪ Connection StringConnection String▪ SQL CommandsSQL Commands

ConnectionConnection – the address of your DatasourceDatasource (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 = @"Provider=Microsoft.Jet.OLEDB.4.0;" + @"Data source= C:\Documents and Settings\username\" + @"My Documents\AccessFile.mdb";

try { conn.Open(); } catch (Exception ex) { MessageBox.Show("Failed to connect to data

source"); }

finally { conn.Close(); } }

Call an Call an instance of instance of ADO.Net ADO.Net

namespacenamespace

Create the Create the ‘string’ ‘string’ address for

address for your databaseyour database

Try Catch Try Catch Statement 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