Technology Questions

Primary key constraint ensures that the column(s) always has a unique value to identify the record.
Example:
Below, the primary key is created for column id with name prim_id.
create table employee ( id number NOT NULL, Name varchar(200) Constraint prim_id primary key(id) );

Value type :

• Stores the data


• The value of value types is stored on the managed stack


• They are lighter objects 


• One variable can have only one value

Reference Type :

• Stores the reference to the data


• A reference type is allocated on the heap


• They are heavier objects


• Several variables can reference the same data

Each application gets its own Linux user ID and virtual machine which means that the application code runs in isolation from other applications.

Notices: These are trivial, non-critical errors that PHP encounters while executing a script - for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all - although, as you will see, you can change this default behaviour.

Warnings: These are more serious errors - for example, attempting to include() a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination.

Fatal errors: These are critical errors - for example, instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP’s default behaviour is to display them to the user when they take place.

yes if the method is ovreriding method

no if the method is not overriding method

Layer objects are data objects which represent visual content. Layer objects are used by views to render their content. Custom layer objects can also be added to the interface to implement complex animations and other types of sophisticated visual effects.

You can prevent a class from overriding in C# by using the sealed keyword; whereas, the NotInheritable keyword is used to prevent a class from overriding in Visual Basic.