Difference Between Trigger and Procedure in DBMS

Last Updated : 30 Sep, 2024

In Relational Database Management Systems (RDBMS), triggers and procedures are two important elements necessary for data manipulation. Still, there are vast differences between them, although many individuals cannot tell the difference because their uses are quite similar. On the other hand, trigger are actions that are fired in response to some specific event occurring to the database, whilst procedures are programmes that exist and need to be invoked by the user. It is important to understand the difference between a trigger and a procedure when using a database in order to have a smooth running system.

What is Triggers?

A trigger in DBMS is a set of instructions that are set ‘to trigger’ or execute automatically in response to one or the other events taking place in the database. Such events can be operations such as: INSERT, UPDATE or DELETE upon a specific table or view. Triggers can also be specified to run before or after running the trigger event depending on the desired action. It is usually applied for business rules’ enforcement and for ensuring data consistency and updating tasks, which should occur because of modification of data, in the organization.

Types of Triggers

Before Triggers: These are performed before the operation is done or before an operation such as INSERT, UPDATE OR DELETE is performed. They can be used to check the values of input data and even transform this data before it is inserted into or updated in the database.
After Triggers: These are invoked after the operation is over. They are effective in activities that involve capturing any modification or exercising functions based on the event—firing or calling other events.
Instead of Triggers: These supplant the firing event, which in turn means that the intended operation (INSERT, UPDATE, DELETE) does not occur, but instead the action of the trigger is executed. These are usually applied with views to compel specific kinds of logic.

Advantages of Triggers

Protection of data
Inhibits transactions that are not valid
It also keeps the different tables in sync.
Referential integrity is enforced with the use of triggers.
Triggers can also be used in event logging and auditing.

Disadvantages of Trigger

Complex Debugging: Debugging may be challenging because triggers run automatically and users do not pin point how they are performing their actions.
Performance Overhead: Many triggers are bad for database performance, particularly for high-transaction systems.
Hidden Execution: This is because while the execution of triggers takes place behind the scene, failure to document their execution may cause some odd behaviors.

What is Procedures?

A procedure is a known as stored procedure, which is a sequence of SQL statements which in case needed can be used more than once. One of them is that compared to other forms of programming, procedures are called directly by the user or the application for the purpose of executing some particular operation. As a result of using them, it is easier to encapsulate logic for performing operations in a database. Procedures, unlike triggers, can not be initiated upon any event except when a user or an application program calls for the procedure.

Advantages of Procedures

A Stored Procedure can be used as modular programming, which means that it can be created once, stored, and called multiple times as needed. This allows for speedier execution.
Reduces network traffic
Improving data security
Easy to maintain because the stored procedure scripts are all in one place and hence, it is easy to update and track dependencies when schema changes occur.
Testing can be carried out independent of the application.

Disadvantages of Procedures

Manual Execution: It is essential to call procedures manually, which might be annoying in cases where something needs to be done automatically.
Less Flexibility in Event-Handling: They cannot be invoked as triggers do whenever some event happens, and therefore are not very useful for tasks that need constant updates.

Difference Between Triggers and Procedures

Parameters	Triggers	Procedures
Basics	A Trigger is implicitly invoked whenever any event such as INSERT, DELETE, or UPDATE occurs in a TABLE.	A Procedure is explicitly called by the user/application using statements or commands such as exec, EXECUTE, or simply procedure name
Action	When an event occurs, a trigger helps to execute an action automatically.	A procedure helps to perform a specified task when it is invoked.
Define/ call	Only nesting of triggers can be achieved in a table. We cannot define/call a trigger inside another trigger.	We can define/call procedures inside another procedure.
Syntax	In a database, the syntax to define a trigger: CREATE TRIGGER TRIGGER_NAME	In a database, the syntax to define a procedure: CREATE PROCEDURE PROCEDURE_NAME
Transaction statements	Transaction statements such as COMMIT, ROLLBACK, and SAVEPOINT are not allowed in triggers.	All transaction statements such as COMMIT and ROLLBACK are allowed in procedures.
Usage	Triggers are used to maintain referential integrity by keeping a record of activities performed on the table.	Procedures are used to perform tasks defined or specified by the users.
Return value	We cannot return values in a trigger. Also, as an input, we cannot pass values as a parameter.	We can return 0 to n values. However, we can pass values as parameters.

Conclusion

Overall, triggers and procedures for DBMS have different functions. Triggers are defined in response to particular events and run as soon as particular change happens in the database, which makes them appropriate to be used to keep state of data and perform various tasks. While procedures are pre-defined code that must be hand-triggered and are suitable for repeatable, modular actions.

Difference between Selection and Projection in DBMS

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