When learning SQL, there are ideas and concepts you must know. If I ask you... what's DML? What's the difference between DML and DDL? You need to know what they are and be able to articulate what each does. If I ask you... What's Transact-SQL? You need to know it's Microsoft's flavor of SQL. If I ask you... what's a data type? You need to know what that is and be able to provide examples. For example... what's the difference between varchar and nvarchar? Interviewers won't have patience for candidates who don't know the basics. They will simply move on to the next candidate. My Transact-SQL course and associated study guide has all of this. You have zero excuses for not having all the basics memorized.

SQL isn't complicated until you get to authoring stored procedures that are hundreds of lines long. However, for most of us, that isn't going to happen. Thankfully. With that said, you still need to know a lot about it. You need to know a lot about the language and a lot about databases themselves. Almost all data stores speak SQL at some level. All relational database use SQL and so do all data warehouses. Here are five easy SQL questions you must know. 1) What's a primary key? 2) What's a clustered index? 3) Why is structured data? 4) What's a data type? 5) How are tables related in a relational database? If you've taken my Transact-SQL course then you'll know these. If not, then that's where you start. If you miss the softball questions (the easy ones), you won't make it past this interview I promise. SQL is the single most important skill machine learning engineers need. Machine learning is about data, not modeling.

For those taking my SQL course, here is the location of the AdventureWorks database .bak files. You can download the one you want and restore it to your local instance. https://learn.microsoft.com/en-us/sql/samples/adventureworks-install-configure?view=sql-server-ver16&tabs=ssms If you navigate down this page it will show you how to restore it.

SQL is one of the top skills for data professionals and that includes the machine learning engineer. Without heavy SQL knowledge you won't work in machine learning or any other data role for that matter.