Does anyone have any suggestions on the best resources to use to get me back up to speed, ideally books?
Thanks
One of my favorites to get the very basics is Select Star, especially because you work with real and meaningful data: https://selectstarsql.com/
Use the Index, Luke has also really helped me make queries that don't waste a ton of time: https://use-the-index-luke.com/
Microsoft also has a bunch of paid training classes for MSSQL, if you or your boss don't mind ponying up some $$$. MSSQL is an amazing tool, and it's worth it to really learn how to use it well.
Good luck!
By far, the best actionable resource I used. Google search for answers/explanations & theory