clickhouse中的标准方法是使用嵌套结构，并从使用数组连接的结构中进行选择。
clickhouse中的underhood嵌套字段只是一组长度相同的数组。
样品：
创建这样的表

CREATE TABLE performance_metrics
(
    timestamp DateTime, 
    website String, 
    custom_events Nested (
        metric String,
        value UInt64  -- actually you can have more attributes here, if needed
    )
)
ENGINE = MergeTree
PARTITION BY toMonday(timestamp)
ORDER BY (website, timestamp);

将数据作为多个数组引用嵌套的子字段。这些数组的名称应以嵌套名称作为前缀，长度应相同：

INSERT INTO performance_metrics (timestamp, website, custom_events.metric, custom_events.value)  VALUES
( '2019-02-04 10:00:00', 'google.com',        ['a', 'b', 'c'],[10,20,30]),
( '2019-02-04 10:00:01', 'stackoverflow.com', ['b', 'c', 'd'],[22,29,40]),
( '2019-02-04 10:00:01', 'google.com',        ['a','d'], [8,42]);

现在您可以使用array join从性能指标中选择：

SELECT 
    website, 
    custom_events.metric, 
    median(custom_events.value), 
    min(timestamp), 
    max(timestamp)
FROM performance_metrics 
ARRAY JOIN custom_events
GROUP BY 
    website, 
    custom_events.metric
ORDER BY 
    website ASC, 
    custom_events.metric ASC