Technology Questions

UNION selects only distinct values whereas UNION ALL selects all values and not just distinct ones

Super global arrays are the built in arrays that can be used anywhere. They are also called as auto-global as they can be used inside a function as well. The arrays with the longs names such as $HTTP_SERVER_VARS, must be made global before they can be used in an array. This $HTTP_SERVER_VARS check your php.ini setting for long arrays.

A database trigger is procedural code that is automatically executed in response to certain events on a particular table or view in a database. The trigger is mostly used for maintaining the integrity of the information on the database.

Syntax:

CREATE OR REPLACE TRIGGER [Trigger Name] [Before / After / Instead Of]

ON [schema].[table]

<PL/SQL subprogram>

Types of PL/SQL triggers : 

> Row trigger          - The trigger fires for each ROW affected.

> Statement trigger - The trigger is fired once when the condition is matched

> Before and After trigger - The BEFORE trigger run the trigger action before the insert, update or delete statement. The AFTER trigger runs the trigger action after the insert, update or delete statement is executes.

True, the given statement that xml preserves white spaces is correct.

COM is the component Object Model is a system whch creates application which are binary form that is language independent , object oriented ,modular and reusable .

Primary key : a relational database constraint. Primary key consists of one or more columns that uniquely identify a row in the table. For a normalized relation, there is one designated primary key.

Unique index: a physical object that stores only unique values. There can be one or more unique indexes on a table.