SQL aggregations index Aggregations APPROX_DISTINCT APPROX_MEDIAN APPROX_PERCENTILE ARBITRARY AVG BOOL_AND BOOL_OR CHECKSUM CORRELATION COUNT COUNT_IF COVAR_POP COVAR_SAMP GROUP_CONCAT KURTOSIS MAX MAX_BY MIN MIN_BY REGR_AVGX REGR_AVGY REGR_COUNT REGR_INTERCEPT REGR_R2 REGR_SLOPE REGR_SXX REGR_SXY REGR_SYY SKEWNESS STD_POP STD_SAMP STDEV SUM VAR_POP VAR_SAMP VARIANCE