Blind injection (time difference, delayed injection)
Time difference injection, also known as delayed injection, is a blind injection technique.
Submit the function sql statement that is impressed by the execution time, and judge whether the execution is successful by the length of the execution time. For example, if it is correct, it will take a long time, and if it is wrong, it will lead to a short execution time. This is the so-called advanced blind note.
Using BENCHMARK sleep function to inject
Using sleep can also cause a denial of service
