Why we use the Trigger and what it's uses?
A database trigger is procedural code that is automatically executed in response to certain events on a particular table in a database. Triggers can restrict access to specific data, perform logging, or audit data modifications. Triggers supplement the standard capabilities of your database to provide a highly customized database management system. For example, you can use triggers to:
1)Automatically generate derived column values.
2)Enforce referential integrity across nodes in a distributed database
3)Enforce complex business rules
4)Provide transparent event logging
6)Maintain synchronous table replicates
7)Gather statistics on table access
8)Modify table data when DML statements are issued against views
9)Publish information about database events, user events, and SQL statements to subscribing applications
10)Restrict DML operations against a table to those issued during regular business hours
11)Enforce security authorizations
12)Prevent invalid transactions