555*if(now()=sysdate(),sleep(39.572),0)

Here’s what that expression does in MySQL-like syntax:

• 555* ... multiplies the result of the IF by 555.
• IF(cond, a, b) returns a if cond is true, otherwise returns b.
• now() and sysdate() both return the current date/time (slightly different timing semantics in some versions).
• sleep(39.572) pauses execution for 39.572 seconds and returns 0.
• If the condition is true, the inner part evaluates to sleep(39.572) (so the query sleeps for ~39.6 seconds, then yields 0). If false, it yields 0 immediately.

So, in typical cases:

• The condition now() = sysdate() is often true within the same statement, causing a ~39.572-second delay.
• The result of the IF is 0 in either case (sleep returns 0, or the false branch is 0), and then you multiply by 555 to get 0.

In short: this is a time-delay payload. It mostly delays the response by about 39.6 seconds, and the final numeric result is 0.

Note: This kind of construct is associated with time-based blind SQL injection tests. Use only in safe, authorized environments (e.g., your own lab) and with proper defensive practices (prepared statements, parameterized queries, input validation).