https://selectstarsql.com/ is an interactive book which aims to be the best place on the internet for learning SQL. It helps you learn by running queries against a real-world dataset to complete projects of consequence. It is free of charge, free of ads and doesn't require registration or downloads.
The Linux Command Line and Adventures with the Linux Command Line, both by William Shotts, are a nice read for beginner linux administartion
http://www.linuxcommand.org/tlcl.php/