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Documentation
/ SQL
/ Query Syntax
SAMPLE Clause
The SAMPLE
clause allows you to run the query on a sample from the base table. This can significantly speed up processing of queries, at the expense of accuracy in the result. Samples can also be used to quickly see a snapshot of the data when exploring a data set. The sample clause is applied right after anything in the FROM
clause (i.e., after any joins, but before the WHERE
clause or any aggregates). See the SAMPLE
page for more information.
Examples
Select a sample of 1% of the addresses table using default (system) sampling:
SELECT *
FROM addresses
USING SAMPLE 1%;
Select a sample of 1% of the addresses table using bernoulli sampling:
SELECT *
FROM addresses
USING SAMPLE 1% (bernoulli);
Select a sample of 10 rows from the subquery:
SELECT *
FROM (SELECT * FROM addresses)
USING SAMPLE 10 ROWS;