• Getting started finding a vulnerable parameter: https://github.com/AdmiralGaust/SQL-Injection-cheat-sheet
• Master list: https://www.netsparker.com/blog/web-security/sql-injection-cheat-sheet/
• General list: https://portswigger.net/web-security/sql-injection/cheat-sheet
• UNION attacks https://portswigger.net/web-security/sql-injection/union-attacks
• Continued...

Helpful reference material:

• Info gathering: https://portswigger.net/web-security/sql-injection/examining-the-database
• Blind injections: https://portswigger.net/web-security/sql-injection/blind
• General SQL tips & tricks: https://sqlzoo.net/
• Juice Shop hints: https://bkimminich.gitbooks.io/pwning-owasp-juice-shop/part2/injection.html

Helpful reference material: