Derby 

You can store application logic in a database and then load classes from the 
database.

Step 1: create your application jar file
jar cf travelagent.jar travelagent/*.class

Step 2:
Add the jar file or files to the database. when you install jar file in
database, you give it a Derby jar name, which is SQL92Identifier.

CALL sqlj.install_jar('tours.jar', 'APP.Sample1', 0)

Step 3: Enable database class loading by setting the property
        "derby.database.classpath" :

CALL SYSCS_UTIL.SYSCS_SET_DATABASE_PROPERTY(
    'derby.database.classpath',
    'APP.ToursLogic:APP.ACCOUNTINGLOGIC')

Note:
Derby's class loader looks first in the user's classpath for any needed classes,
and then in the database.

Step 4:

Question: Is class loading from db only for embedded db or for network db also?

Question:


Derby Server side programming :

  - database side JDBC procedures can be defined and called within SQL
    statements. They are, then, executed in derby server side.

  - The database side method calls following to get current connection:
    Connection conn = DriverManager.getConnection("jdbc:default:connection");
    This connection is called nested connection and always has its
    autocommit mode set to false.

 
Trigger action overview
  CREATE TRIGGER . . .
DELETE FROM flightavailability 
	WHERE flight_id IN (SELECT flight_id FROM flightavailability 
		WHERE YEAR(flight_date) < 2005);) 

Many trigger actions need to access the values of the rows being changed.
Such trigger actions need to know one or both of the following:
	 	
* the "before" values of the rows being changed (their values before the 
  database event that caused the trigger to fire)

* the "after" values of the rows being changed (the values to which the 
  database event is setting them)

JDBC Transacations Model
  - By default JDBC connection autocommit is enabled, so each sql is transaction.
  - Use conn.setAutoCommit(false) to disable autocommit.
  - Connection conn.commit, conn.rollback can be called explicitly

    

- (updatabale) Result Set can be used to delete/update values as well:
    
   Statement stmt = conn.createStatement(ResultSet.TYPE_FORWARD_ONLY, 
           ResultSet.CONCUR_UPDATABLE); 
   ResultSet uprs = stmt.executeQuery( "SELECT FIRSTNAME, LASTNAME, WORKDEPT, BONUS " + "FROM EMPLOYEE"); 

   while (uprs.next()) { 
      int newBonus = uprs.getInt("BONUS") + 100;
      uprs.updateInt("BONUS", newBonus); 
      uprs.updateRow();  // or uprs.deleteRow(); 
   }

- (scrollable updatable) result set can also move cursors to anywhere ...
  Statement stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, 
                                        ResultSet.CONCUR_UPDATABLE);
  ResultSet uprs = stmt.executeQuery(
    "SELECT FIRSTNAME, LASTNAME, WORKDEPT, BONUS " +
    "FROM EMPLOYEE");

  uprs.absolute(5); // update the fifth row
  int newBonus = uprs.getInt("BONUS") + 100;
  uprs.updateInt("BONUS", newBonus);
  uprs.updateRow();

- Default derby isolation level is TRANSACTION_READ_COMMITTED

- Derby supports XML data type.

- Does derby SQL support Begin; ... End; syntax ?

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