ClickHouse/tests/queries/0_stateless/02812_subquery_operators.sql

SELECT singleValueOrNull(toNullable(''));
SELECT singleValueOrNull(toNullable('Hello'));
SELECT singleValueOrNull((SELECT 'Hello'));
SELECT singleValueOrNull(toNullable(123));
SELECT '' = ALL (SELECT toNullable(''));
SELECT '', ['\0'], [], singleValueOrNull(( SELECT '\0' ) ), [''];