内置的聚合函数

返回类型    函数 说明 bigint count(*),count(expr),count(disTINCT expr[,  expr_.,expr_.]) 返回记录条数。 double sum(col),sum(disTINCT col) 求和 avg(col),avg(disTINCT col) 求平均值 min(col) 返回指定列中最小值 max(col) 返回指定列中最大值 var_pop(col) 返回指定列的方差 var_samp(col) 返回指定列的样本方差 stddev_pop(col) 返回指定列的偏差 stddev_samp(col) 返回指定列的样本偏差 covar_pop(col1,col2) 两列数值协方差 covar_samp(col1,245); overflow:hidden"> 两列数值样本协方差 corr(col1,245); overflow:hidden"> 返回两列数值的相关系数 percentile(col,p) 返回数值区域的百分比数值点。0<=P<=1,否则返回NULL,不支持浮点型数值。 array<double> normal; font-size:14px; padding:4px; border:1px solid rgb(227,array(p~1,\ [,p,2,]…)) 返回数值区域的一组百分比值分别对应的数值点。0<=P<=1,245); overflow:hidden"> percentile_approx(col,p[,B]) Returns an approximate p^th^ percentile of a  numeric column (including floating point types) in the group. The B parameter  controls approximation accuracy at the cost of memory. Higher values yield  better approximations,and the default is 10,000. When the number of distinct  values in col is smaller than B,this gives an exact percentile value. Same as above,but accepts and returns an array  of percentile values instead of a single one. array<struct\{‘x’,'y’\}> histogram_numeric(col,b) Computes a histogram of a numeric column in the  group using b non-uniformly spaced bins. The output is an array of size b of  double-valued (x,y) coordinates that represent the bin centers and heights array collect_set(col) 返回无重复记录

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