Explain different types of Triggers in SQL/PL SQL.

Triggers in SQL/PL SQL are database objects that are automatically executed or fired when certain events occur. They are used to maintain the integrity of the data in the database. There are several types of triggers in SQL/PL SQL:

1. Before Trigger (or) Pre Trigger: These triggers fire before the DML (Data Manipulation Language) event (Insert, Update, Delete) is executed. They are used when we want to perform a certain action before the event.

2. After Trigger (or) Post Trigger: These triggers fire after the DML event is executed. They are used when we want to perform a certain action after the event.

3. Instead of Trigger: These triggers fire in place of the DML event. They are used when we want to override the action of the DML event. These are commonly used with views.

4. Row Level Trigger: These triggers fire for each row affected by the DML operation. For example, if an update statement affects 10 rows, the trigger will fire 10 times.

5. Statement Level Trigger: These triggers fire once for each DML operation, regardless of the number of rows affected. For example, if an update statement affects 10 rows, the trigger will fire only once.

6. Schema Level Trigger: These triggers fire when there is a change in the schema of the database. For example, when a table is created or dropped.

7. Database Level Trigger: These triggers fire when there is a change in the database, such as a logon or logoff event.

Each of these triggers can be useful in different scenarios, depending on the specific requirements of the database system.