Sure, here's an SQL topic and question you can explore:

Topic: Joins in SQL

Question:

You're working with a database that stores information about customers and their orders. The customers table has columns for customer ID, name, and email. The orders table has columns for order ID, customer ID (foreign key referencing the customers table), order date, and total amount.

Write a SQL query to find the total number of orders placed by each customer along with their email address.

Keywords like : self join , outer join (right outer join , left outer join , full outher join ) , inner join , natural join 

Others topics like 

What is SQL

Statements or components in sql

• Data Query Language 
• Data Manipulation Language 
• Data Definition Language 
• Data control Language 
• Transaction Control Language 

Insert update delete modifiy Create drop alter rename truncate

20 to 30 Query per topics  

Clauses : 

• Select Clause 
• Where Clause 
• Order by Clause 
• Given by Clause 
• Having Clause