Question: What Are The Triggers In SQL?

How do you create a trigger?

Creating TriggersCREATE [OR REPLACE] TRIGGER trigger_name − Creates or replaces an existing trigger with the trigger_name.{BEFORE | AFTER | INSTEAD OF} − This specifies when the trigger will be executed.

{INSERT [OR] | UPDATE [OR] | DELETE} − This specifies the DML operation.More items….

Triggers can cause performance issues if not written carefully and not enough developers are knowledgeable enough to write them well. … Triggers are often slower than other means of maintaining data integrity, so if you can use a check constraint, use that instead of a trigger.

What are cursors in SQL?

A cursor holds the rows (one or more) returned by a SQL statement. The set of rows the cursor holds is referred to as the active set. You can name a cursor so that it could be referred to in a program to fetch and process the rows returned by the SQL statement, one at a time.

What is SQL Query Injection?

What is SQL injection (SQLi)? SQL injection is a web security vulnerability that allows an attacker to interfere with the queries that an application makes to its database. It generally allows an attacker to view data that they are not normally able to retrieve.

What are triggers in SQL with examples?

Trigger: A trigger is a stored procedure in database which automatically invokes whenever a special event in the database occurs. For example, a trigger can be invoked when a row is inserted into a specified table or when certain table columns are being updated.

What are the types of triggering?

Types of TriggersData Manipulation Language (DML) Triggers. DML triggers are executed when a DML operation like INSERT, UPDATE OR DELETE is fired on a Table or View. … Data Definition Language (DDL) Triggers. … LOGON Triggers. … CLR Triggers.

What trigger means?

Triggers are anything that remind someone of previous trauma. To be triggered is to have an intense emotional or physical reaction, such as a panic attack, after encountering a trigger. Related words: content warning. safe space.

What are the two types of triggers?

There are two types of triggers.BEFORE trigger: – This trigger is called before the execution of the DML statement. … After Trigger: – this trigger is called after once DML statement is executed. … Combination of triggers: – We can have combination of row, statement, BEFORE and AFTER triggers.

Can we write commit in trigger?

Trigger should not commit and cannot commit. Committing in a trigger usually raises an exception unless it happens into autonomous transaction. When you open connection, Oracle creates session for it.

What are the types of triggers in SQL?

Types of Triggers in OracleDML Trigger: It fires when the DML event is specified (INSERT/UPDATE/DELETE)DDL Trigger: It fires when the DDL event is specified (CREATE/ALTER)DATABASE Trigger: It fires when the database event is specified (LOGON/LOGOFF/STARTUP/SHUTDOWN)

What is the main purpose of triggers in database?

A database trigger is procedural code that is automatically executed in response to certain events on a particular table or view in a database. The trigger is mostly used for maintaining the integrity of the information on the database.

What is purpose of triggers?

Triggers are used to maintain the referential integrity of data by changing the data in a systematic fashion. Each trigger is attached to a single, specified table in the database. Triggers can be viewed as similar to stored procedures in that both consist of procedural logic that is stored at the database level.