PL/SQL (Procedural Language/Structured Query Language) is an extension of SQL that enables developers to write procedural code and implement business logic within an Oracle database. Here are some of the key topics to learn in PL/SQL:

1. PL/SQL blocks and variables: Learn how to create and execute PL/SQL blocks and how to declare variables within them.

2. Control structures: Learn how to use control structures such as IF/THEN, CASE, LOOP, WHILE, and FOR to control the flow of a PL/SQL program.

3. Cursors: Learn how to use cursors to retrieve and manipulate data from the database.

4. Exception handling: Learn how to handle errors and exceptions that may occur during the execution of a PL/SQL program.

5. Stored procedures and functions: Learn how to create and call stored procedures and functions within a PL/SQL program.

6. Packages: Learn how to use packages to organize related procedures, functions, and types in a modular and reusable way.

7. Triggers: Learn how to use triggers to execute PL/SQL code in response to database events such as INSERT, UPDATE, and DELETE.

8. Dynamic SQL: Learn how to use dynamic SQL to generate SQL statements dynamically at runtime.

9. Collections: Learn how to use collections such as arrays, nested tables, and associative arrays to store and manipulate data within a PL/SQL program.

10. Advanced features: Learn about advanced features such as object types, subprograms, and PL/SQL optimization techniques.