Description
The Hash output format calculates a single hash value for all columns and rows of the result.
This is useful for calculating a "fingerprint" of the result, for example in situations where data transfer is the bottleneck.
Example usage
Reading data
Consider a table football with the following data:
┌───────date─┬─season─┬─home_team─────────────┬─away_team───────────┬─home_team_goals─┬─away_team_goals─┐
1. │ 2022-04-30 │ 2021 │ Sutton United │ Bradford City │ 1 │ 4 │
2. │ 2022-04-30 │ 2021 │ Swindon Town │ Barrow │ 2 │ 1 │
3. │ 2022-04-30 │ 2021 │ Tranmere Rovers │ Oldham Athletic │ 2 │ 0 │
4. │ 2022-05-02 │ 2021 │ Port Vale │ Newport County │ 1 │ 2 │
5. │ 2022-05-02 │ 2021 │ Salford City │ Mansfield Town │ 2 │ 2 │
6. │ 2022-05-07 │ 2021 │ Barrow │ Northampton Town │ 1 │ 3 │
7. │ 2022-05-07 │ 2021 │ Bradford City │ Carlisle United │ 2 │ 0 │
8. │ 2022-05-07 │ 2021 │ Bristol Rovers │ Scunthorpe United │ 7 │ 0 │
9. │ 2022-05-07 │ 2021 │ Exeter City │ Port Vale │ 0 │ 1 │
10. │ 2022-05-07 │ 2021 │ Harrogate Town A.F.C. │ Sutton United │ 0 │ 2 │
11. │ 2022-05-07 │ 2021 │ Hartlepool United │ Colchester United │ 0 │ 2 │
12. │ 2022-05-07 │ 2021 │ Leyton Orient │ Tranmere Rovers │ 0 │ 1 │
13. │ 2022-05-07 │ 2021 │ Mansfield Town │ Forest Green Rovers │ 2 │ 2 │
14. │ 2022-05-07 │ 2021 │ Newport County │ Rochdale │ 0 │ 2 │
15. │ 2022-05-07 │ 2021 │ Oldham Athletic │ Crawley Town │ 3 │ 3 │
16. │ 2022-05-07 │ 2021 │ Stevenage Borough │ Salford City │ 4 │ 2 │
17. │ 2022-05-07 │ 2021 │ Walsall │ Swindon Town │ 0 │ 3 │
└────────────┴────────┴───────────────────────┴─────────────────────┴─────────────────┴─────────────────┘
Read data using the Hash format:
SELECT *
FROM football
FORMAT Hash
The query will process the data, but will not output anything.
df2ec2f0669b000edff6adee264e7d68
1 rows in set. Elapsed: 0.154 sec.
