Aggregate functions
Aggregate functions compute a single result from a set of input values.
For details about the supported syntaxes of aggregate expressions, see Aggregate expressions.
General-purpose aggregate functions
array_agg
Returns an array from input values in which each value in the set is assigned to an array element. The ORDER BY clause is optional and specifies the order of rows processed in the aggregation, which determines the order of the elements in the result array.
array_agg ( expression [ ORDER BY [ sort_expression { ASC | DESC } ] ] ) -> output_array
avg
Returns the average (arithmetic mean) of the selected values.
avg ( expression ) -> see description
Input types include smallint, int, bigint, numeric, real, and double precision.
Return type is numeric for integer inputs and double precision for float point inputs.
bit_and
Returns the bitwise AND of all non-null input values or null if no non-null values are provided.
bit_and ( smallint, int, or bigint ) -> same as input type
bit_or
Returns the bitwise OR of all non-null input values or null if no non-null values are provided.
bit_or ( smallint, int, or bigint ) -> same as input type
bool_and
Returns true if all input values are true, otherwise false.
bool_and ( boolean ) -> boolean
bool_or
Returns true if at least one input value is true, otherwise false.
bool_or ( boolean ) -> boolean
count
Returns the number of non-null rows.
count ( expression ) -> bigint
The input can be of any supported data type.
jsonb_agg
Aggregates values, including nulls, as a JSON array. The ORDER BY clause is optional and specifies the order of rows processed in the aggregation, which determines the order of the elements in the result array.
jsonb_agg ( any_element ) -> jsonb
jsonb_object_agg
Aggregates name/value pairs as a JSON object.
jsonb_object_agg ( key "string" , value "any" ) -> jsonb
max
Returns the maximum value in a set of values.
max ( expression ) -> same as input type
Input can be of any numeric, string, date/time, or interval type, or an array of these types.
min
Returns the minimum value in a set of values.
min ( expression ) -> same as input type
Input can be of any numeric, string, date/time, or interval type, or an array of these types.
string_agg
Combines non-null values into a string, separated by delimiter_string. The ORDER BY clause is optional and specifies the order of rows processed in the aggregation, which determines the order of the elements in the result array.
string_agg ( expression, delimiter_string ) -> output_string
sum
Returns the sum of all input values.
sum ( expression )
Input types include smallint, int, bigint, numeric, real, and double precision.
Return type is bigint for smallint or int inputs, numeric for bigint inputs, otherwise the same as the input data type.
Aggregate functions for statistics
stddev_pop
Calculates the population standard deviation of the input values. Returns NULL if the input contains no non-null values.
stddev_pop ( expression ) -> output_value
stddev_samp
Calculates the sample standard deviation of the input values. Returns NULL if the input contains fewer than two non-null values.
stddev_samp ( expression ) -> output_value
var_pop
Calculates the population variance of the input values. Returns NULL if the input contains no non-null values.
var_pop ( expression ) -> output_value
var_samp
Calculates the sample variance of the input values. Returns NULL if the input contains fewer than two non-null values.
var_samp ( expression ) -> output_value
Ordered-set aggregate functions
At present, ordered-set aggregate functions support only constant fraction arguments.
mode
Computes the mode, which is the most frequent value of the aggregated argument. If there are multiple equally-frequent values, it arbitrarily chooses the first one.
mode () WITHIN GROUP ( ORDER BY sort_expression anyelement ) -> same as sort_expression
sort_expression: Must be of a sortable type.
This example calculates the mode of the values in column1 from table1.
SELECT mode() WITHIN GROUP (ORDER BY column1) FROM table1;
percentile_cont
At present, percentile_cont is not supported for streaming queries yet.
Computes the continuous percentile, which is a value corresponding to the specified fraction within the ordered set of aggregated argument values. It can interpolate between adjacent input items if needed.
percentile_cont ( fraction double precision ) WITHIN GROUP ( ORDER BY sort_expression double precision ) -> double precision
fraction: The fraction value representing the desired percentile. It should be between 0 and 1.
This example calculates the median (50th percentile) of the values in column1 from table1.
SELECT percentile_cont(0.5) WITHIN GROUP (ORDER BY column1) FROM table1;
If NULL is provided, the function will not calculate a specific percentile and return NULL instead.
percentile_disc
At present, percentile_disc is not supported for streaming queries yet.
Computes the discrete percentile, which is the first value within the ordered set of aggregated argument values whose position in the ordering equals or exceeds the specified fraction.
percentile_disc ( fraction double precision ) WITHIN GROUP ( ORDER BY sort_expression anyelement ) -> same as sort_expression
fraction: The fraction value representing the desired percentile. It should be between 0 and 1.
sort_expression: Must be of a sortable type.
This example calculates the 75th percentile of the values in column1 from table1.
SELECT percentile_disc(0.75) WITHIN GROUP (ORDER BY column1) FROM table1;
If NULL is provided, the function will not calculate a specific percentile and return NULL instead.
Grouping operation functions
Grouping operation functions are used in conjunction with grouping sets to distinguish result rows. The arguments to the grouping() function are not actually evaluated, but they must exactly match expressions given in the GROUP BY clause of the associated query level.
grouping
Returns a bit mask indicating which GROUP BY expressions are not included in the current grouping set. Bits are assigned with the rightmost argument corresponding to the least-significant bit; each bit is 0 if the corresponding expression is included in the grouping criteria of the grouping set generating the current result row, and 1 if it is not included.
grouping ( group_by_expression(s) ) → integer
Example
CREATE TABLE items_sold (brand varchar, size varchar, sales int);
INSERT INTO items_sold VALUES ('Foo', 'L', 10),('Foo', 'M', 20),('Bar', 'M', 15),('Bar', 'L', '5');
SELECT brand, size, sum(sales), grouping(brand), grouping(size), grouping(brand,size), count(DISTINCT sales)
FROM items_sold
GROUP BY GROUPING SETS ((brand), (size), ());
------RESULTS
Bar NULL 20 0 1 1 2
Foo NULL 30 0 1 1 2
NULL L 15 1 0 2 2
NULL M 35 1 0 2 2
NULL NULL 50 1 1 3 4
