How to Intentionally Create a Long-Running MySQL Query

I assume you could use benchmark() for this, although that isn't the scope of it.

select benchmark(9999999999, md5('when will it end?'));

If you need them to run for a bit, but not that long, then try

select benchmark(1000000, md5('when will it end?')); -- around 0.3s
select benchmark(10000000, md5('when will it end?')); -- around 3s
select benchmark(100000000, md5('when will it end?')); -- around 30s