CHECKSUM
Calculates a hash value known as a checksum operation on a list of arguments. When *
is specified as an argument - calculates checksum over all columns in the input. Performing a checksum operation is useful for warming up table data or to check if the same values exist in two different tables.
Syntax
CHECKSUM( <expression1> [, <expression2>] [, <expression3>] [, ...<expressionN>] )
CHECKSUM(*)
Example
For this example, we’ll create a new table albums
as shown below.
CREATE DIMENSION TABLE albums (year INTEGER, artist TEXT, title TEXT);
INSERT INTO
albums
VALUES
(1982, 'Michael Jackson', 'Thriller'),
(1973, 'Pink Floyd', 'The Dark Side of the Moon'),
(1969, 'The Beatles', 'Abbey Road'),
(1976, 'Eagles', 'Hotel California');
The example below calculates a checksum based on all columns in the table albums
.
SELECT CHECKSUM(*) FROM albums;
Returns: 1630068993470241196
The next example calculates a checksum based on columns year
and title
only.
SELECT CHECKSUM(year, title) FROM albums;
Returns: 4056287705143712538