enable_* 会话设置

SET enable_json_ast_dialect = 1;
SET dialect = 'clickhouse_json';

-- Subsequent queries are parsed as JSON ASTs:
{"type":"SelectWithUnionQuery", ...}

CREATE TABLE TAB(C1 Int, C2 Int, ALL Int) ENGINE=Memory();

INSERT INTO TAB VALUES (10, 20, 30), (20, 20, 10), (30, 10, 20);

SELECT * FROM TAB ORDER BY ALL; -- returns an error that ALL is ambiguous

SELECT * FROM TAB ORDER BY ALL SETTINGS enable_order_by_all = 0;

┌─C1─┬─C2─┬─ALL─┐
│ 20 │ 20 │  10 │
│ 30 │ 10 │  20 │
│ 10 │ 20 │  30 │
└────┴────┴─────┘

SELECT
    count()
FROM events
WHERE (_part, _part_offset) IN (
    SELECT _part, _part_offset
    FROM events
    WHERE user_id = 42
)