Technology Questions

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.

PHP: Hypertext Preprocessor is open source server-side scripting language that is widely used for web development. PHP scripts are executed on the server. PHP allows writing dynamically generated web pages efficiently and quickly. The syntax is mostly borrowed from C, Java and perl. PHP is free to download and use.

main() method is called by the JVM even before the instantiation of the class, hence it is declared as static.

I/O operations like reading or writing a file is not possible with client-side javascript. However , this can be done by coding a Java applet that reads files for the script. 

Customer Information Control System (CICS) is an online transaction processing monitor from IBM that acts as an interface between the operating system and application programs to provide rapid high-volume online transaction processing.

GROUP BY partitions the selected rows on the distinct values of the column on which you group by. HAVING selects GROUPs which match the criteria specified

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.