Junior Level

Creating databases and tables

Data Types; Char vs varchar, storing date in DB

Retrieving data with SELECT statement

Inserting data with INSERT statement

Updating data with UPDATE statement

Removing data with DELETE statement

Junior Strong Level

SQL Joins (INNER, LEFT)

ORDER BY

DISTINCT

Middle Level

Indices, unique indices and primary keys

Relationships (One-to-one, One-to-many, Many-to-many)