Aggregate Functions
AVG
AVG ([DISTINCT] expression)Parameters
-
DISTINCT- optional keyword. If presents, will average the unique values.
Description
The average (mean) value. If no rows are selected, the result is NULL. Aggregates are only allowed in select statements. The returned value is of the same data type as the parameter.
Examples
Calculating average players' age:
SELECT AVG(age) "AverageAge" FROM Players;BIT_AND
BIT_AND (expression)Description
The bitwise AND of all non-null values. If no rows are selected, the result is NULL. Aggregates are only allowed in select statements.
A logical AND operation is performed on each pair of corresponding bits of two binary expressions of equal length.
In each pair, it returns 1 if the first bit is 1 AND the second bit is 1. Else, it returns 0.
BIT_OR
BIT_OR (expression)Description
The bitwise OR of all non-null values. If no rows are selected, the result is NULL. Aggregates are only allowed in select statements.
A logical OR operation is performed on each pair of corresponding bits of two binary expressions of equal length.
In each pair, the result is 1 if the first bit is 1 OR the second bit is 1 OR both bits are 1, and otherwise the result is 0.
BOOL_AND
BOOL_AND (boolean)Description
Returns true if all expressions are true. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements.
Example
SELECT item, BOOL_AND(price > 10) FROM Items GROUP BY item;BOOL_OR
BOOL_AND (boolean)Description
Returns true if any expression is true. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements.
Example
SELECT BOOL_OR(CITY LIKE 'W%') FROM Users;COUNT
COUNT (* | [DISTINCT] expression)Description
The count of all entries or of the non-null values. This method returns a long. If no entries are selected, the result is 0. Aggregates are only allowed in select statements.
Example
Calculate the number of players in every city:
SELECT city_id, COUNT(*) FROM Players GROUP BY city_id;GROUP_CONCAT
GROUP_CONCAT([DISTINCT] expression || [expression || [expression ...]]
[ORDER BY expression [ASC|DESC], [[ORDER BY expression [ASC|DESC]]]
[SEPARATOR expression])The expression can be a concatenation of columns and strings using the || operator, for example: column1 || "=" || column2.
Parameters
-
DISTINCT- filters the result set for unique sets of expressions. -
expression- specifies an expression that may be a column name, a result of another function, or a math operation. -
ORDER BY- orders rows by expression. -
SEPARATOR- overrides a string separator. By default, the separator character is the comma ','.
Description
Concatenates strings with a separator. The default separator is a ',' (without whitespace). This method returns a string. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements.
Example
Group all players' names in one row:
SELECT GROUP_CONCAT(name ORDER BY id SEPARATOR ', ') FROM Players;MAX
MAX (expression)Parameters
-
expression- may be a column name, a result of another function, or a math operation.
Description
Returns the highest value. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements. The returned value is of the same data type as the parameter.
Example
Return the height of the tallest player:
SELECT MAX(height) FROM Players;MIN
MIN (expression)Parameters
-
expression- may be a column name, the result of another function, or a math operation.
Description
Returns the lowest value. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements. The returned value is of the same data type as the parameter.
Example
Return the age of the youngest player:
SELECT MIN(age) FROM Players;SUM
SUM ([DISTINCT] expression)Parameters
-
DISTINCT- accumulate unique values only. -
expression- may be a column name, the result of another function, or a math operation.
Description
Returns the sum of all values. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements. The data type of the returned value depends on the parameter data.
Example
Get the total number of goals scored by all players:
SELECT SUM(goal) FROM Players;SELECTIVITY
SELECTIVITY (expression)Parameters
-
expression- may be a column name.
Description
Estimates the selectivity (0-100) of a value. The value is defined as (100 * distinctCount / rowCount). The selectivity of 0 rows is 0 (unknown). Aggregates are only allowed in select statements.
Example
Calculate the selectivity of the first_name and second_name columns:
SELECT SELECTIVITY(first_name), SELECTIVITY(second_name) FROM Player
WHERE ROWNUM() < 20000;STDDEV_POP
STDDEV_POP ([DISTINCT] expression)Parameters
-
DISTINCT- calculate unique value only. -
expression- may be a column name.
Description
Returns the population standard deviation. This method returns a double. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements.
Example
Calculate the standard deviation for Players' age:
SELECT STDDEV_POP(age) from Players;STDDEV_SAMP
STDDEV_SAMP ([DISTINCT] expression)Parameters
-
DISTINCT- calculate unique values only. -
expression- may be a column name.
Description
Calculates the sample standard deviation. This method returns a double. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements.
Example
Calculates the sample standard deviation for Players' age:
SELECT STDDEV_SAMP(age) from Players;VAR_POP
VAR_POP ([DISTINCT] expression)Parameters
-
DISTINCT- calculate unique values only. -
expression- may be a column name.
Description
Calculates the population variance (square of the population standard deviation). This method returns a double. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements.
Example
Calculate the variance of Players' age:
SELECT VAR_POP (age) from Players;VAR_SAMP
VAR_SAMP ([DISTINCT] expression)Parameters
-
DISTINCT- calculate unique values only. -
expression- may be a column name.
Description
Calculates the sample variance (square of the sample standard deviation). This method returns a double. If no entries are selected, the result is NULL. Aggregates are only allowed in select statements.
Example
Calculate the variance of Players' age:
SELECT VAR_SAMP(age) FROM Players;