There are a lot of good books on SQL, so you can choose for a long time. This is a great guide considers the techniques of database design for mere developers, and methods of optimization of loads for system administrators.
The book covers the following topics:
✔ select, insert, update and delete data;
✔ working with strings;
✔ work with date and time;
✔ indexes and transactions;
✔ database administration and more.
➕ relevant material on the topic;
➕ definitive guide to MySQL;
➕ numerous examples.