CREATE DATABASE IF NOT EXISTS test; DROP TABLE IF EXISTS test.one; CREATE TABLE test.one(dummy UInt8) ENGINE = Memory; SELECT x, t.name FROM (SELECT name, database AS x FROM system.tables) AS t ALL INNER JOIN (SELECT name AS x FROM system.databases) AS db USING x WHERE x = 'system' AND t.name = 'one' FORMAT PrettyCompactNoEscapes; SELECT x, t.name FROM (SELECT name, database AS x FROM system.tables) AS t JOIN (SELECT name AS x FROM system.databases) AS db USING x WHERE x = 'system' AND t.name = 'one' SETTINGS join_default_strictness = 'ALL' FORMAT PrettyCompactNoEscapes; SET join_default_strictness = 'ALL'; SELECT database, t.name FROM (SELECT * FROM system.tables) AS t JOIN (SELECT name, name AS database FROM system.databases) AS db USING database WHERE db.name = 'system' AND t.name = 'one' FORMAT PrettyCompactNoEscapes; --SELECT db.name, t.name -- FROM (SELECT name, database AS x FROM system.tables) AS t -- JOIN (SELECT name AS x FROM system.databases) AS db USING x -- WHERE x = 'system' AND t.name = 'one' -- FORMAT PrettyCompactNoEscapes; SELECT t.name --, db.name FROM (SELECT name, database FROM system.tables WHERE name = 'one') AS t JOIN (SELECT name FROM system.databases WHERE name = 'system') AS db ON t.database = db.name; --SELECT db.name, t.name -- FROM system.tables AS t -- JOIN (SELECT * FROM system.databases WHERE name = 'system') AS db ON t.database = db.name -- WHERE t.name = 'one'; SELECT database, t.name FROM system.tables AS t JOIN (SELECT name, name AS database FROM system.databases) AS db ON t.database = db.name WHERE t.name = 'one'; SELECT count(t.database) FROM (SELECT * FROM system.tables WHERE name = 'one') AS t JOIN system.databases AS db ON t.database = db.name; --SELECT count(db.name) -- FROM system.tables AS t -- JOIN system.databases AS db ON t.database = db.name -- WHERE t.name = 'one'; SELECT count() FROM system.tables AS t JOIN system.databases AS db ON db.name = t.database WHERE t.name = 'one'; DROP TABLE test.one;