SELECT DISTINCT #
SELECT DISTINCT is specified, all duplicate rows are removed from the result set (one row is kept from each group of duplicates).
SELECT DISTINCT id FROM Orders
For streaming queries, the required state for computing the query result might grow infinitely. State size depends on number of distinct rows. You can provide a query configuration with an appropriate state time-to-live (TTL) to prevent excessive state size. Note that this might affect the correctness of the query result. See query configuration for details