select arr[rand()%length(arr)+1] from 
(select ['a', 'b', 'c'] as arr);

import sshtunnel as sshtunnel
from clickhouse_driver import connect

with sshtunnel.SSHTunnelForwarder(
    ('localhost', 22),
    ssh_username="root",
    ssh_password="root",
    remote_bind_address=('localhost', 9000)) as server:

    local_port = server.local_bind_port
    print(local_port)


    conn = connect(host='localhost', port=local_port, database='ertb', user='default', password='')

    cursor = conn.cursor()
    cursor.execute('SHOW TABLES')
    print(cursor.fetchall())

SELECT *
FROM test

┌───────Date─┬─Name─┐
│ 2020-06-02 │ A    │
│ 2020-06-01 │ A    │
│ 2020-06-03 │ B    │
│ 2020-06-02 │ B    │
│ 2020-06-03 │ C    │
│ 2020-06-02 │ C    │
│ 2020-06-01 │ C    │
└────────────┴──────┘

7 rows in set. Elapsed: 0.004 sec. 

SET joined_subquery_requires_alias = 0

Ok.

0 rows in set. Elapsed: 0.001 sec. 


SELECT 
    Name, 
    groupArray(flag)
FROM 
(
    SELECT 
        Name, 
        sum(Date = Date2) AS flag
    FROM 
    (
        SELECT 
            *, 
            1 AS joinusingme
        FROM test
        INNER JOIN 
        (
            SELECT 
                Date AS Date2, 
                1 AS joinusingme
            FROM test
            GROUP BY Date
        ) USING (joinusingme)
    )
    GROUP BY 
        Name, 
        Date2
    ORDER BY 
        Name ASC, 
        Date2 DESC
)
GROUP BY Name

┌─Name─┬─groupArray(flag)─┐
│ B    │ [1,1,0]          │
│ C    │ [1,1,1]          │
│ A    │ [0,1,1]          │
└──────┴──────────────────┘

3 rows in set. Elapsed: 0.004 sec.