Java

Class Access

What does it mean to access a class?

When we say code from one class (class A) has access to another class (class B), it means class A can do one of three things.

▪ Createan instance of class B

▪ Extend class B (in other words, become a subclass of class B)

▪ Access certain methods and variables within class B, depending on the access control of thosemethods and variables

dependiendo del control de acceso de los métodos y variables

In efect, access means visibility. If class A can’t see class B, the access level of the methods and variableswithin class B won’t matter; class A won’t have any way to access those methods and variables.

Using Variables

TSQL recognizes two types of variables: local and global

Local variables: arecreated by the user. Local variables are recognized by a @ preceding the name.These user-defined variables continue to exist until the end of the current batch.

Global variables: are system-defined andare always available. These system variables are preceded by two @@. Global variables are assigned their values by the system and users should not attempt to change these assignments.

DECLARE@apellido varchar(30)

Select @apellido =’Perez’

TRIGGERS

1. What is a trigger?

A trigger is a set of SQL statements that is executed when an insert, update or delete occurs on a table.2. What is the maximum number of triggers that can be applied to a single table?

3

3. How are triggers and stored procedures similar?

They recognize the same set of SQLcommands.

SP and triggers both batch together sets of related SQL statements.

4. Prior to version 6 of SQL Server, what was the primary use of triggers?

Enforcing referentialintegrity.

5. What is the purpose of the CREATE TRIGGER portion of the CREATE TRIGGER statement?

The CREATE TRIGGER clause establishes ownership of the trigger and assigns a name to the...