SET send_logs_level = 'fatal'; SELECT (SELECT (SELECT (SELECT (SELECT (SELECT count() FROM (SELECT * FROM system.numbers LIMIT 10)))))) = (SELECT 10), ((SELECT 1, 'Hello', [1, 2]).3)[1]; SELECT toUInt64((SELECT 9)) IN (SELECT number FROM system.numbers LIMIT 10); SELECT (SELECT toDate('2015-01-02')) = toDate('2015-01-02'), 'Hello' = (SELECT 'Hello'); SELECT (SELECT toDate('2015-01-02'), 'Hello'); SELECT (SELECT toDate('2015-01-02'), 'Hello') AS x, x, identity((SELECT 1)), identity((SELECT 1) AS y); -- SELECT (SELECT uniqState('')); SELECT ( SELECT throwIf(1 + dummy) ); -- { serverError 395 } -- Scalar subquery with 0 rows must return Null SELECT (SELECT 1 WHERE 0); -- But tuple and array can't be inside nullable SELECT (SELECT 1, 2 WHERE 0); -- { serverError 125 } SELECT (SELECT [1] WHERE 0); -- { serverError 125 } -- Works for not-empty casle SELECT (SELECT 1, 2); SELECT (SELECT [1]); -- Several rows SELECT (SELECT number FROM numbers(2)); -- { serverError 125 }