What are different types of cursors in PL/SQL and when would you use each type?

In PL/SQL, there are mainly three types of cursors:

1. **Explicit Cursors**:
Explicit cursors are explicitly declared by the programmer. They provide more control over the result set and allow fetching records one by one. Explicit cursors are typically used in scenarios where one needs to process rows individually or update records based on specific conditions within a loop.

2. **Implicit Cursors**:
Implicit cursors are automatically generated by the Oracle server when DML statements like SELECT, INSERT, UPDATE, or DELETE are executed without explicitly declaring a cursor. They are suitable for simple queries where there is no need for manual cursor management.

3. **REF CURSOR**:
Ref Cursors (Reference Cursors) are pointers to result sets. They are used to pass query result sets between PL/SQL programs or to pass result sets to calling programs. Ref cursors are especially useful when you want to return a dynamic result set from a stored procedure or function.

When choosing the appropriate cursor type in PL/SQL, consider the complexity of the query, the need for manual cursor management, and the requirement to pass result sets between programs. Each cursor type has its strengths and use cases, so selecting the right one will depend on the specific requirements of your PL/SQL program.

Optimizing your PL/SQL code with the suitable cursor type can enhance performance and efficiency. Make sure to effectively leverage explicit, implicit, or REF cursors based on your application needs to achieve optimal results.