trigger in SQL server

Question

what is trigger and how to use it?

Sonu Gupta · Accepted Answer

Hi,   Go to below links -   https://www.c-sharpcorner.com/UploadFile/a53f1a/triggers-in-sql-server/   https://www.codeproject.com/Articles/25600/Triggers-SQL-Server   https://www.tutorialspoint.com/plsql/plsql_triggers.htm

Rajanikant Hawaldar · Answer

Hi Harish, A SQL trigger is a set of SQL statements stored in the database catalog. A SQL trigger is executed or fired whenever an event associated with a table occurs e.g., insert, update or delete. That means when insert, update, delete data in table performing some actions on table which are associated with this table.   Lets say for example if you insert exit formalities(When employee leave company) of employee then triggering event to delete employee data from all table. Refer below links.   A SQL trigger is a special type of stored procedure. It is special because it is not called directly like a stored procedure. The main difference between a trigger and a stored procedure is that a trigger is called automatically when a data modification event is made against a table whereas a stored procedure must be called explicitly.   SQL triggers provide an alternative way to check the integrity of data. SQL triggers can catch errors in business logic in the database layer. SQL triggers provide an alternative way to run scheduled tasks. By using SQL triggers, you don’t have to wait to run the scheduled tasks because the triggers are invoked automatically before or after a change is made to the data in the tables. SQL triggers are very useful to audit the changes of data in tables   http://www.mysqltutorial.org/mysql-insert-statement.aspx http://www.mysqltutorial.org/mysql-update-data.aspx http://www.mysqltutorial.org/mysql-delete-statement.aspx http://www.mysqltutorial.org/mysql-stored-procedure-tutorial.aspx

satheesh d · Answer

Triggers are stored programs which are get exceuted automatically when some events occurs. This triggers is helps to maintain the integrity of the data.  Let us consider that the table consists of studentname and mark is obtained. If any new records are added to the table then the mark should increase by 50 than the new inserted value. For this we can use trigger to solve this query. CREATE TRIGGER Addmarks    BEFORE INSERT     ON StudentMarks    FOR EACH ROW    SET  new .Marks =  new .Marks+50;   After executing this trigger, whenever any new records are added, the corresponding marks are increased by 50 with the inserted value.