In data analysis, before and after triggers are important as they provide a unique way to look at data, allowing you to compare different data points. You can look at the mean, median, or percentile of a data set before and after you perform a trigger.
Before and after triggers are used to access the data points in a data set. You can find values of a data set before and after you perform a trigger, which can be used to compare two data sets.
Summary Table
| Before | After |
| fired to validate a condition before the update | fired after the change has occurred |
| for every row affected by the update | for only the changed rows |
| more suited for transactional database systems | more suited for non-transactional database systems |
In this article, we will learn the differences between before and after triggers, we will see how they are used, and why they are important.
What is Before Trigger?
Validating a record before inserting into the database is a good practice to prevent data integrity issues.
You can validate the record in a before insert trigger. This is different from an after insert trigger. In this trigger, you can validate the record before inserting into the database.
What is After Trigger?
After trigger is a trigger that runs after the record is inserted into the database. In this trigger, you can run your custom code after inserting the record into the database. This is different from a before trigger. In this trigger, accessing data in the database is limited to a select, insert, update, or delete operation.
The Similarities Between Before and After Trigger
Before trigger and after trigger are similar in a way that both of them allow you to access data and validate it against a set of conditions.
Let’s see how they are similar.
The use
Before trigger and after trigger are used to execute some actions before or after a set of actions happen. The Before trigger is used to validate data against a set of conditions and the After trigger is used to display data on the screen.
The action
Before trigger and after trigger are used to perform a specific action on the specified data at the start of an event or before a set of events that take place during a certain time period.
The condition
Before trigger and after trigger are used to check if the specified data meets a set of conditions. The condition is the basis for checking if the data is valid or not. It is also used to check if the specified data has been modified.
The result
Before trigger and after trigger are used to execute a set of actions when the condition is met. The result is the same as the action.
Before Trigger VS After Trigger
Now that you know the similarities, let’s take a look at the differences between before trigger and after trigger.
The timing
Before trigger is fired to validate a condition before the update or change occurs to the data. After trigger is fired after the change has occurred.
The scope of the trigger
Before trigger is fired for every row affected by the update or change. After trigger is fired for only the changed rows.
The usage of triggers vs transactions
Before triggers are more suited for transactional database systems. In a transactional database system, you need to ensure that all the updates and changes are processed before the transaction is committed. In a non-transactional database system, you can use before triggers to validate your data without worrying about transactions.
