Understanding SQLi Payloads: https://www.db-fiddle.com/f/nLpyQDMd49iRygnY9H7CB8/5

Guided Lab: https://portswigger.net/web-security/sql-injection/blind/lab-conditional-responses

Challenge Lab: https://portswigger.net/web-security/sql-injection/blind/lab-time-delays