Difference between Row level and Statement level triggers
Triggers are very essential in the management of database operations since they provide for the automation of tasks and business rules. Triggers can be defined to occur on either the ‘before’ or the ‘after’ creation of a record using typical database activities such as inserting, updating, or deleting records. There are two main types of triggers: Row-level triggers and Statement-level triggers.
In this article, we will learn about the differences between these triggers and some pros and cons of each so that we can choose which of the two to use in our application.
What is a Row-Level Trigger?
A Row-level trigger fires once for each for row in the database affected by a particular operation. In the case of `DELETE`, `UPDATE`, or `INSERT` operations, the row-level trigger is fired multiple times depending on the number of rows impacted.
Advantages of Row-Level Triggers
- Granular control: ROW level triggers allow getting exact control over each record of a table, therefore is useful at places where row-by-row check is necessary for example, while auditing and validations.
- Customization: These triggers permit operation that is flexible based on the selection of a row or a single database row as the case may be.
- Suitable for complex calculations: Preferred if you want to generate a calculation or an update on some specific row.
Disadvantages of Row-Level Triggers
- Performance overhead: This is because row-level triggers run for each row hence are not efficient when dealing with large sets of data.
- Complexity: The management of row-level triggers for bulk operations is a possible point of development of problems and increased complexity in code logic.
What is Statement-Level Trigger?
A Statement-level trigger fires once for each SQL statement executed and this is irrespective to the number of rows to have been changed. Whether one row or many rows are inserted, updated or deleted, the statement-level trigger fires a single time based on the statement.
Advantages of Statement-Level Triggers
- Efficient execution: Since the trigger fires only once for a statement it can benefit when operating on a large amount of rows.
- Simpler logic: Appropriate for situations where you don’t have to work with individual rows of the data, but you need something done on an SQL operation.
- Lower overhead: Another important aspect is that at reduced number of execution(s) carried out on the call, there are lesser computations involved, particularly for large sets/tuples or other types of data.
Disadvantages of Statement-Level Triggers
- Less granular control: At the same time, statement-level triggers do not include the option for row-level control Therefore, when there is a need for field-by-field validation, or individual rows to be processed separately, this is not possible to achieve using statement-level triggers alone.
- Limited use cases: Because of this, triggers are not very efficient when used in cases such as detailed auditing or per-row validation.
Difference between Row level and Statement level triggers
| Row Level Triggers | Statement Level Triggers |
|---|---|
| Row level triggers executes once for each and every row in the transaction. | Statement level triggers executes only once for each single transaction. |
| Specifically used for data auditing purpose. | Used for enforcing all additional security on the transactions performed on the table. |
| “FOR EACH ROW” clause is present in CREATE TRIGGER command. | “FOR EACH STATEMENT” clause is omitted in CREATE TRIGGER command. |
| Example: If 1500 rows are to be inserted into a table, the row level trigger would execute 1500 times. | Example: If 1500 rows are to be inserted into a table, the statement level trigger would execute only once. |
Conclusion
Row-level as well as statement level trigger found to be useful for database management in certain circumstances. Row-level triggers are most appropriate for cases where, for one reason or the other, there is need to process the rows individually without having to address all other rows collectively, hence convenience in such cases comes from using row-level triggers. Statement-level triggers are most effective in cases where there is need to process many rows at once but without having to handle each row one at a time i. e. many rows all at once hence saving time is best achieved using Selection of a good type of trigger depends on the granularity that the application requires, performance issues that an application has, and the level of complexity that the application has.
Difference between Row level and Statement level triggers-FAQ’s
That brings us to the last question which is when should you use row-level triggers?
Row-level triggers are useful in a situation where you have to carry out certain operations on the individuals rows affected in a row process, like in the case of auditing, validation or computational tasks.
It is crucial to understand whether it is possible to reap performance gains with the help of row-level triggers.
This is correct, due to the fact that they perform for every modified row, they can in some times add to the performance cost particularly as it pertains to a big table.
What do we use statement-level triggers for?
If the action you require should happen once per SQL operation and regardless of the number of records then statement-level triggers are best to implement this with requirements such as logging or very general business rules.
Are it possible to inactivate a row-level trigger when a statement-level triggers runs in the same table?
Yes, one can use both the LDM and the TIM triggers on the same table but then the two have to be handled well so that they do not cause an intertur structure conflict or intertur function interference.
