Question

20*if(now()=sysdate(),sleep(15),0)

Answer 1

The expression you provided is a SQL query snippet. Here's a breakdown of what it does:

- `if(now()=sysdate(), sleep(15), 0)`: This part checks if the current time (using `now()`) is the same as the system time (`sysdate()`). If they are equal (which would occur if the server is executing this statement in a way that the times are exactly the same), it will call the `sleep(15)` function, which pauses execution for 15 seconds. If the times are not equal, it returns `0`.

- Multiplying the result of the `if` statement by `20`: The whole expression effectively multiplies the outcome of the `if` statement by `20`. This means:
- If the condition is true, the result will be `20 * 15 = 300` (because `sleep(15)` doesn’t return a numeric value, and the multiplier has no effect on a sleep operation.)
- If the condition is false, the result will be `20 * 0 = 0`.

This kind of expression might be used in certain contexts to create a delay during the execution of a SQL command, however, it is generally not a good practice to use such expressions directly within SQL for purposes like controlling flow, as it can lead to inefficient queries.

If this snippet is meant to be part of an SQL injection attack, it may aim to disrupt the application or database performance by intentionally causing a delay. Always ensure proper security measures are in place to prevent such vulnerabilities.