Aggregate functions in Cloud Dataflow SQL

An aggregate function is a function that performs a calculation on a set of values. COUNT, MIN and MAX are examples of aggregate functions.

SELECT COUNT(*) as total_count, COUNT(fruit) as non_null_count,
       MIN(fruit) as min, MAX(fruit) as max
FROM UNNEST([NULL, "apple", "pear", "orange"]) as fruit;
+-------------+----------------+-------+------+
| total_count | non_null_count | min   | max  |
+-------------+----------------+-------+------+
| 4           | 3              | apple | pear |
+-------------+----------------+-------+------+

The following sections describe the aggregate functions that Cloud Dataflow SQL supports.

AVG

AVG(expression)

Description

Returns the average of non-NULL input values.

Supported Argument Types

FLOAT64. Note that, for floating point input types, the return result is non-deterministic, which means you might receive a different result each time you use this function.

Returned Data Types

  • FLOAT64

Examples

SELECT AVG(x) as avg
FROM UNNEST([0, 2, NULL, 4, 4, 5]) as x;

+-----+
| avg |
+-----+
| 3   |
+-----+

COUNT

1. COUNT(*)

2. COUNT(expression)

Description

  1. Returns the number of rows in the input.
  2. Returns the number of rows with expression evaluated to any value other than NULL.

Supported Argument Types

expression can be any data type.

Return Data Types

INT64

Examples

SELECT COUNT(*) AS count_star, COUNT(x) AS count_x
FROM UNNEST([1, 4, NULL, 4, 5]) AS x;

+------------+---------+
| count_star | count_x |
+------------+---------+
| 5          | 4       |
+------------+---------+


MAX

MAX(expression)

Description

Returns the maximum value of non-NULL expressions. Returns NULL if there are zero input rows or expression evaluates to NULL for all rows.

Supported Argument Types

Any data type except: ARRAY STRUCT

Return Data Types

Same as the data type used as the input values.

Examples

SELECT MAX(x) AS max
FROM UNNEST([8, NULL, 37, 4, NULL, 55]) AS x;

+-----+
| max |
+-----+
| 55  |
+-----+


MIN

MIN(expression)

Description

Returns the minimum value of non-NULL expressions. Returns NULL if there are zero input rows or expression evaluates to NULL for all rows.

Supported Argument Types

Any data type except: ARRAY STRUCT

Return Data Types

Same as the data type used as the input values.

Examples

SELECT MIN(x) AS min
FROM UNNEST([8, NULL, 37, 4, NULL, 55]) AS x;

+-----+
| min |
+-----+
| 4   |
+-----+


SUM

SUM(expression)

Description

Returns the sum of non-null values.

If the expression is a floating point value, the sum is non-deterministic, which means you might receive a different result each time you use this function.

Supported Argument Types

Any supported numeric data types.

Return Data Types

  • Returns INT64 if the input is an integer.
  • Returns FLOAT64 if the input is a floating point value.

Returns NULL if the input contains only NULLs.

Examples

SELECT SUM(x) AS sum
FROM UNNEST([1, 2, 3, 4, 5, 4, 3, 2, 1]) AS x;

+-----+
| sum |
+-----+
| 25  |
+-----+


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