stddev (expl)
Returns the standard deviation of the expr expression
MySQL > select stddev(scan_rows) from log_statis group by datetime; +---------------------+ | stddev(`scan_rows`) | +---------------------+ | 2.3736656687790934 | +---------------------+ MySQL > select stddev_pop(scan_rows) from log_statis group by datetime; +-------------------------+ | stddev_pop(`scan_rows`) | +-------------------------+ | 2.3722760595994914 | +-------------------------+
STDDEV,STDDEV_POP,POP