  Random uniform sampling has been studied in various statistical tasks but few
of them have covered the Q-error metric for cardinality estimation (CE). In
this paper, we analyze the confidence intervals of random uniform sampling with
and without replacement for single-table CE. Results indicate that the upper
Q-error bound depends on the sample size and true cardinality. Our bound gives
a rule-of-thumb for how large a sample should be kept for single-table CE.
