Triggers in SQL | Edureka
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Triggers are SQL codes that automatically execute in response to certain events on a specific table, helping maintain data integrity. The document outlines the syntax for creating, using, and dropping triggers, as well as advantages like data validation and disadvantages such as increased database overhead. Examples of trigger operations, including before and after actions, are also provided.
![SYNTAX
OF TRIGGER
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Create Trigger Trigger_Name
(Before | After)
[ Insert | Update | Delete]
on [Table_Name]
[ for each row | for each column ]
[ Trigger_body ]](https://image.slidesharecdn.com/triggers-200105052017/85/Triggers-in-SQL-Edureka-21-320.jpg)
Triggers in SQL | Edureka
- 2. WHAT IS A TRIGGER? SYNTAX AND EXAMPLE OPERATION ON TRIGGERS ADVANTAGES AND DISADVANTAGES www.edureka.co
- 4. Triggers are the SQL codes that are automatically executed in response to certain events on a particular table. These are used to maintain the integrity of the data. What is a TRIGGER? www.edureka.co
- 5. WHAT IS A TRIGGER? Hey Sharan, Do you know what Triggers are? www.edureka.co
- 6. WHAT IS A TRIGGER? www.edureka.co Well, Let me explain you in a simple way www.edureka.co
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- 21. SYNTAX OF TRIGGER www.edureka.co Create Trigger Trigger_Name (Before | After) [ Insert | Update | Delete] on [Table_Name] [ for each row | for each column ] [ Trigger_body ]
- 22. EXAMPLE OF TRIGGER CREATE TRIGGER sample_trigger before INSERT ON student FOR EACH ROW SET new.marks = new.marks+6; www.edureka.co
- 23. NESTED TRIGGERS www.edureka.co Nested Triggers in SQL are the actions that automatically executed when a certain database operation is performed
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- 25. www.edureka.co SYNTAX: DROP TRIGGER trigger name; EXAMPLE: DROP TRIGGER calculate name; We can use DROP command to remove a trigger from the database DROP
- 26. www.edureka.co We can use SHOW command to display triggers from the database DISPLAY SYNTAX: SHOW TRIGGERS IN database_name; EXAMPLE: SHOW TRIGGERS IN edureka;
- 27. www.edureka.co SYNTAX: CREATE TRIGGER calculate before INSERT ON student FOR EACH ROW SET new.marks = new.marks+100; Before Insert Triggers are used to update or validate record values before they’re saved to the database INSERT
- 28. www.edureka.co SYNTAX: CREATE TRIGGER total_mark after insert ON student FOR EACH ROW insert into Final_mark values(new.marks); After Insert Triggers are used to access field values that are set by the system and to effect changes in other records INSERT
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- 30. ADVANTAGES OF TRIGGERS 02 Triggers check the integrity of data 01 Forcing security approvals on the table 03 Counteracting invalid exchanges 04 Triggers handle errors 05 Triggers are useful for inspecting the data www.edureka.co
- 31. DISADVANTAGES OF TRIGGERS Overhead Triggers may increase the overhead of the database Validation Triggers can only provide extended validations, i.e, not all kind validations Troubleshoot Triggers can be difficult to troubleshoot because they execute automatically in the database www.edureka.co
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