In this chapter, we discussed most of the SQL statements and features that are normally used when working with a database.

First, we discussed the statements that are used to modify data: INSERT, UPDATE, REPLACE, and DELETE. Then we learned the basis of transactions, a mechanism used to isolate the operations performed by different connections to avoid conflicts between them. We also examined foreign keys, a way to guarantee data integrity and automate some operations on correlated tables.

Then, we discussed the statements used to query data: simple SELECT, JOIN, UNION, and finally, subqueries.

Furthermore, we examined the most commonly used MariaDB operators that are needed to write or read data. We also learned how to perform some common operations on temporal values.

In the last section, we discussed comments. While comments are commonly seen as a way to write annotations in the code, MariaDB and MySQL support what they call executable comments. Thanks to this feature, we can use...