Every job I've applied to wants me to know SQL, so I'm glad that I did a tutorial. It's very efficient and clean/clear. 
I feel like there's a lot more to it than I'm getting out of these basic tutorials. This website let me use
an actual database which was helpful: http://pgexercises.com/ I kinda had though that SQL was mostly just a database
retrieval language thing, but it looks like it's a lot more developmental than I had anticipated. There's lots of add-ons,
like a Columnstore Index and stuff. I have a lot more to learn but I think it will be useful. Actually I know it will be 
useful if I want a job. 
<3