USE test; DROP TABLE IF EXISTS table1; DROP TABLE IF EXISTS table2; CREATE TABLE table1 ( id String ) ENGINE = Log; CREATE TABLE table2 ( parent_id String ) ENGINE = Log; insert into table1 values ('1'); SELECT table2.parent_id = '', isNull(table2.parent_id) FROM table1 ANY LEFT JOIN table2 ON table1.id = table2.parent_id; SET join_use_nulls = 1; SELECT table2.parent_id = '', isNull(table2.parent_id) FROM table1 ANY LEFT JOIN table2 ON table1.id = table2.parent_id; DROP TABLE test.table1; DROP TABLE test.table2;