Difference Between Triggers and Stored Procedures
In a database, a trigger is a process or code segment that is carried out on its own when some particular event happens in a view or table. There are other uses for triggers as they are usually applied for maintaining consistency in a database. On the other hand, a stored procedure is a procedure that is used by applications making use of a relational database. Normally, they are used as a process for validating information and controlling access to the database.
Triggers are executed automatically when the event that the trigger is thought to respond to happens, whereas in order to execute a stored procedure a certain EXECUTE or CALL statement needs to be made. In addition, it is important to understand that debugging triggers are a very tough task and are considered to be harder than debugging stored procedures. Also, triggers are very handy if you wish to make sure that a certain thing happens when a particular event occurs.
Triggers are generally used to enforce business regulations, auditing changes in the database and replicating information as well. A very well known trigger is Data Manipulation Language (DML) that activate when data is interrupted. A number of database systems support non data triggers, which are caused when Data Definition Language (DDL) events happen. A few examples are triggers that are established when views are made, during rollback operations or commit. They are also used for auditing purposes. Moreover, Oracle database system validates schema level triggers. These triggers are made when database schemas are updated like After Creation, After Alter, Before Alter, After Drop, Before Drop among others. The four main kinds of triggers supported by Oracle are Row Level triggers, Each Row Type triggers, For Each Statement Type triggers and Column Level triggers.
Understand that if data processing operation needs a number of SQL statements to be executed, these are implemented as stored procedures. Use a CALL or EXECUTE statement when citing a stored procedure. They are supposed to return results. For instance, results from the SELECT statements which can be later used by applications or other stored procedures. Languages that write them usually support control structures like if, for, while, etc. A variety of languages can be used to implement stored procedures such as PL, SQL, Java in Oracle, T-SQL and .NET Framework in Microsoft SQL Server.