Nested(name1 Type1, Name2 Type2, ...)

SELECT
    Goals.ID,
    Goals.EventTime
FROM test.visits
WHERE CounterID = 101500 AND length(Goals.ID) < 5
ORDER BY VisitID
LIMIT 10

    ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
    ┃ Goals.ID                       ┃ Goals.EventTime                                                                           ┃
    ┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩
 1. │ [1073752,591325,591325]        │ ['2014-03-17 16:38:10','2014-03-17 16:38:48','2014-03-17 16:42:27']                       │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
 2. │ [1073752]                      │ ['2014-03-17 00:28:25']                                                                   │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
 3. │ [1073752]                      │ ['2014-03-17 10:46:20']                                                                   │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
 4. │ [1073752,591325,591325,591325] │ ['2014-03-17 13:59:20','2014-03-17 22:17:55','2014-03-17 22:18:07','2014-03-17 22:18:51'] │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
 5. │ []                             │ []                                                                                        │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
 6. │ [1073752,591325,591325]        │ ['2014-03-17 11:37:06','2014-03-17 14:07:47','2014-03-17 14:36:21']                       │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
 7. │ []                             │ []                                                                                        │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
 8. │ []                             │ []                                                                                        │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
 9. │ [591325,1073752]               │ ['2014-03-17 00:46:05','2014-03-17 00:46:05']                                             │
    ├────────────────────────────────┼───────────────────────────────────────────────────────────────────────────────────────────┤
10. │ [1073752,591325,591325,591325] │ ['2014-03-17 13:28:33','2014-03-17 13:30:26','2014-03-17 18:51:21','2014-03-17 18:51:45'] │
    └────────────────────────────────┴───────────────────────────────────────────────────────────────────────────────────────────┘

-- WRONG: compares the entire Array to a scalar
SELECT * FROM test.visits
WHERE Goals.ID = 591325;

Code: 43. DB::Exception: Illegal types of arguments (`Array(UInt32)`, `UInt32`)
of function `equals`. (ILLEGAL_TYPE_OF_ARGUMENT)

-- Find visits that have at least one goal with ID 591325
SELECT CounterID, VisitID, Goals.ID
FROM test.visits
WHERE has(Goals.ID, 591325);

-- Find visits that have at least one goal with ID greater than 1000000
SELECT CounterID, VisitID, Goals.ID
FROM test.visits
WHERE arrayExists(id -> id > 1000000, Goals.ID);

-- Visits with at least 3 goals
SELECT CounterID, VisitID, Goals.ID
FROM test.visits
WHERE length(Goals.ID) >= 3;

-- Visits with at least one goal (non-empty array)
SELECT CounterID, VisitID, Goals.ID
FROM test.visits
WHERE notEmpty(Goals.ID);

SELECT
    Goal.ID,
    Goal.EventTime
FROM test.visits
ARRAY JOIN Goals AS Goal
WHERE CounterID = 101500 AND length(Goals.ID) < 5
ORDER BY VisitID, Goal.Serial
LIMIT 10

    ┏━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━┓
    ┃ Goal.ID ┃      Goal.EventTime ┃
    ┡━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━┩
 1. │ 1073752 │ 2014-03-17 16:38:10 │
    ├─────────┼─────────────────────┤
 2. │  591325 │ 2014-03-17 16:38:48 │
    ├─────────┼─────────────────────┤
 3. │  591325 │ 2014-03-17 16:42:27 │
    ├─────────┼─────────────────────┤
 4. │ 1073752 │ 2014-03-17 00:28:25 │
    ├─────────┼─────────────────────┤
 5. │ 1073752 │ 2014-03-17 10:46:20 │
    ├─────────┼─────────────────────┤
 6. │ 1073752 │ 2014-03-17 13:59:20 │
    ├─────────┼─────────────────────┤
 7. │  591325 │ 2014-03-17 22:17:55 │
    ├─────────┼─────────────────────┤
 8. │  591325 │ 2014-03-17 22:18:07 │
    ├─────────┼─────────────────────┤
 9. │  591325 │ 2014-03-17 22:18:51 │
    ├─────────┼─────────────────────┤
10. │ 1073752 │ 2014-03-17 11:37:06 │
    └─────────┴─────────────────────┘

INSERT INTO test.visits
    (CounterID, StartDate, Sign, IsNew, VisitID, UserID,
     Goals.ID, Goals.Serial, Goals.EventTime, Goals.Price, Goals.OrderID, Goals.CurrencyID)
VALUES
    -- A visit with two goals: each nested sub-column gets an array of length 2
    (101500, '2014-03-18', 1, 1, 2001, 200001,
     [1073752, 591325], [1, 2],
     ['2014-03-18 10:00:00', '2014-03-18 10:05:00'],
     [100, 200], ['order_a', 'order_b'], [1, 2]),
    -- A visit with no goals: all nested sub-columns get empty arrays
    (101500, '2014-03-18', 1, 0, 2002, 200002,
     [], [], [], [], [], []);

-- ERROR: Goals.ID has 2 elements, but Goals.Serial has 1
INSERT INTO test.visits
    (CounterID, StartDate, Sign, IsNew, VisitID, UserID,
     Goals.ID, Goals.Serial, Goals.EventTime, Goals.Price, Goals.OrderID, Goals.CurrencyID)
VALUES
    (101500, '2014-03-18', 1, 1, 2003, 200003,
     [1073752, 591325], [1],
     ['2014-03-18 12:00:00'], [0], [''], [0]);

ALTER TABLE test.visits ADD COLUMN Goals.Revenue Float64;

ALTER TABLE test.visits DROP COLUMN Goals.Revenue;

ALTER TABLE test.visits MODIFY COLUMN Goals.Price Int32;

-- OK: stays within the Goals structure
ALTER TABLE test.visits RENAME COLUMN Goals.Price TO Goals.Amount;