A comma-separated list of data sources to query.
FROM dataset[,…] [ TABLESAMPLE(percent) ]
A set of data to query, one of the following:
Specifies to return a random sampling of records, where percent specifies the approximate sampling size. The percent value must be between 0 and 100, exclusive, and can include decimal values. The number of records returned is not guaranteed to be the exact percentage specified.
All rows of the data have equal opportunities to be selected. Vertica performs sampling before applying other query filters.
Count all records in
=> SELECT COUNT(*) FROM customer_dimension; COUNT ------- 50000 (1 row)
Return a small sampling of rows in table
=> SELECT customer_name, customer_state FROM customer_dimension TABLESAMPLE(0.5) WHERE customer_state='IL'; customer_name | customer_state ---------------------+---------------- Amy Y. McNulty | IL Daniel C. Nguyen | IL Midori O. Greenwood | IL Meghan U. Lampert | IL Tiffany Y. Lang | IL Laura S. King | IL Steve T. Nguyen | IL Craig S. Webber | IL Luigi A. Lewis | IL Mark W. Williams | IL (10 rows)