HASH_AGG

Calculates a hash value over all rows on a list of arguments. When * is specified as an argument - calculates a hash aggregation over all columns in the input. Performing a hash aggregation operation is useful for warming up table data or to check if the same values exist in two different tables.

Alias: CHECKSUM

Syntax

HASH_AGG( <expression1> [, <expression2>] [, <expression3>] [, ...<expressionN>] )
HASH_AGG(*)

Parameters

Parameter	Description	Supported input types
<expression>	A column name for specific results for the HASH_AGG function to be applied to	Any <column> name

Return Type

BIGINT

Example

For this example, we’ll create a new table tournament_information as shown below.

CREATE DIMENSION TABLE tournament_information (name TEXT, prizedollars DOUBLE PRECISION, tournamentid INTEGER);

INSERT INTO
	tournament_information
VALUES
	('The Snow Park Grand Prix', 20903, 1),
	('The Acceleration Championsip', 19274, 2),
	('The Acceleration Trials', 13877, 3)

The example below calculates a hash aggregation based on all columns in the table tournament_information.

SELECT HASH_AGG(*) FROM tournament_information;

Returns: 1,889,915,309,908,437,919

The next example calculates a hash aggregation based on columns prizedollars and tournamentid only.

SELECT HASH_AGG(prizedollars, tournamentid) FROM tournament_information;

Returns: 3,058,600,455,882,068,351