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What is a “trigger”?
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What is a “trigger”?
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Triggers are stored procedures created in order to enforce integrity rules in a database. A trigger is executed every time a data-modification operation occurs (i.e., insert, update or delete). Triggers are executed automatically on occurance of one of the data-modification operations.
A trigger is a database object directly associated with a particular table. It fires whenever a specific statement/type of statement is issued against that table. The types of statements are insert,update,delete and query statements. Basically, trigger is a set of SQL statements that execute in response to a data modification/retrieval event on a table.
A trigger is a solution to the restrictions of a constraint.
For instance :
1.A database column cannot carry PSEUDO columns as criteria where a trigger can.
2.A database constraint cannot refer old and new values for a row where a trigger can.
Adding to all others here . . .
Other than table triggers there are also schema and database triggers. These can be made to fire when new objects are created, when a user logs in, when the database shutdown etc.
Table level triggers can be classified into row and statement level triggers and those can be further broken down into before and after triggers. Before triggers can modify data.
It is a stored procedure which is automatically fired on a table whenever any DML operation is performed.it is used to prevent any invalid entries of the data in the table.
In a DBMS a trigger is a SQL procedure that initiates an action when an event occurs.
trigger is an event that fires when a DML statement
occurs.
Trigger is a stored procedure program. it excutes
the function one or more automatically.
Trigger is an SQL statement which fires an action when an event occurs.
The event may be insert , update or delet
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