- Salient Notes:
- Unlike Procedure, the Trigger can't take any parameter.
- Procedures and Functions can return any-value , whereas trigger can only return a defined recordset.
- A stored procedure is called explicitly, where as triggers event based and executed automatically.
- A trigger is associated with a Table of a database, where as a procedure may not have any association with the database. ( When we do some internal calculation or assessment, it may run without involving any database)
- It is not possible to track or debug triggers.
The most frequent uses of the triggers are with some events associated with an UPDATE, INSERT or a DELETE functions. These triggers are supposed to implicitly fired depending upon the instructions passed to them.
- Row Level :With each row option, a trigger is engaged at the individual row of a table.
- Statement : Unless "IF FOR EACH ROW" is used Trigger is fired when any row of a table is affected, with a SQL statement.
- Before and After triggers: As the name goes, BEFORE triggers will role before any alteration takes place in a row; whereas AFTER triggers will role after committing row/rows alterations.
- Parameters : Trigger can's accept any parameter , stored function or procedure can.
- Returns : Trigger can't return any value, OUT parameter in procedure and return attribute in a function can return a value to the caller.
- Events: A trigger work likes an event, and is executed before or after a process or function.
- Transaction: A trigger can be used tightly with a transaction, procedures and functions can only be used indirectly.
- Calls : A procedure or function is invoked manually, where as a trigger is always associated widely with any changes in the table.
Now Update the table emp_copy1
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Original Table:
Updated Table:
