Decent quick overview but
This was a decent little overview of sqli, but didn't really touch upon any topics besides mssql. There is also mysql, oracle, etc.. Other topics that could have been mentioned are error based, union based, blind, and sqli in different parts of websites of web forms besides the search box, user agent, cookies, how sqli can be used with xss, uploading shells, WAF bypassing: encoding, double encoding, hexing, etc... While I understand it would be hard to cover all of these in depth, but could quickly go through all of these within an hour.