For all aggregations other than COUNT( * ), NULL and missing values are ignored.
AVG( num_expr )
Computes the average of num_expr for the rows in the group. Num_expr must be numeric.
COUNT( expr )
COUNT( * )
Counts the number of times expr is not NULL in the group. COUNT( * ) returns the total number of rows in the group.
GROUP_CONCAT( expr, <separator = ’,’> )
Concatenates all non-NULL values of expr and returns them as a string. Numeric values of expr are converted to character. If separator is present, it is placed between the values. The default separator is a comma. DISTINCT can be used only with GROUP_CONCAT() if separator is not specified.
MAX( expr )
Returns the maximum value of expr in the group. Expr can be character or numeric.
MIN( expr )
Returns the minimum value of expr in the group. Expr can be character or numeric.
STDDEV_POP( num_expr )
STDDEV_SAMP( num_expr )
SUM( num_expr )
Returns the sum of num_expr for the group. If no non-NULL values are found, SUM() returns NULL.
TOTAL( num_expr )
Same as SUM( num_expr ), except TOTAL() returns 0.0 if no non-NULL values are found.
VAR_POP( num_expr )
VAR_SAMP( num_expr )
Computes the sample variance of num_expr for the group.