A better understanding of SQL changes the database black box perception to a time saver reducing development effort.
I am database specialist helping developers solve their database problems. Many developers still treat databases and SQL as a black box: You write a query with a lot of trial and error, and hopefully the database returns the expected results. The implications of the query's properties or processing in the database are unknown to you. And because of the simple handling of MySQL, MariaDB, PostgreSQL and others, this basic knowledge has always been sufficient!
However you are missing out on many useful features! Some of the operations you have implemented in your application's code could have been done by the database and saved a lot of development time. And when your database has performance problems, expert knowledge is needed. However you don't have to become an expert, knowing a little more will make a big difference. And for this purpose this repository of knowledge has been created, check out all the information and learn anytime you may want to.