:) SELECT version();

┌─version()─┐
│ 20.5.3.27 │
└───────────┘

:) CREATE TABLE test.tuple
(
    `j` Tuple( a Int8, b String)
)
ENGINE = Memory;


Received exception from server (version 20.5.3):
Code: 62. DB::Exception: Received from localhost:9000. DB::Exception: Syntax error (data type): failed at position 9: Int8, b String). Expected one of: LIKE, GLOBAL NOT IN, AS, IS, OR, QuestionMark, BETWEEN, NOT LIKE, AND, Comma, alias, IN, Dot, NOT, Arrow, token, NOT IN, GLOBAL IN.

:) CREATE TABLE test.tuple_from_select
ENGINE = Memory AS
SELECT CAST((1, 'Test'), 'Tuple( a Int8,  b String)') AS j;


Received exception from server (version 20.5.3):
Code: 62. DB::Exception: Received from localhost:9000. DB::Exception: Syntax error (data type): failed at position 9: Int8, b String). Expected one of: LIKE, GLOBAL NOT IN, AS, IS, OR, QuestionMark, BETWEEN, NOT LIKE, AND, Comma, alias, IN, Dot, NOT, Arrow, token, NOT IN, GLOBAL IN.

:) SELECT version();

┌─version()─┐
│ 20.4.6.53 │
└───────────┘

:) CREATE TABLE test.tuple
(
    `j` Tuple( a Int8, b String)
)
ENGINE = Memory;

Ok.

:) SHOW CREATE TABLE test.tuple

┌─statement───────────────────────────────────────────────────────────────────────┐
│ CREATE TABLE test.tuple
(
    `j` Tuple(
    a Int8, 
    b String)
)
ENGINE = Memory │
└─────────────────────────────────────────────────────────────────────────────────┘

:) CREATE TABLE test.tuple_from_select
ENGINE = Memory AS
SELECT CAST((1, 'Test'), 'Tuple( a Int8,  b String)') AS j;

Ok.