Lots of the questions on the forum seem to be about am "I learning the right language. C#, C++, Java etc." In all reality you will learn a language just to use it to connect to a data base!!! So you should be focused on SQL just as much as what ever you think you want to learn as a primary means of programming.
1. Basics like Select, Insert, Update and Delete
2. Joins(INNER, LEFT etc), Unions
3. Stored Procedures, Views and Functions
4. Use of Primary and Foreign Key Relations
5. Data base Normalization.
Make sure you do not focus on one DB learn them all MySQL,MS SQL Server,Postgres and Oracle
The primary tools used to connect and Admin each of the DB's
In your code know how to write the different connection strings and create Data sets, Data tables and Data readers.