SELECT user_id, array_distinct(event_name) AS event_history, flatten(array_distinct(collect_set(items.item_id))) AS cart_history FROM events GROUP BY user_id;

SELECT user_id, collect_set(event_name) AS event_history, array_distinct(flatten(collect_set(items.item_id))) AS cart_history FROM events GROUP BY user_id;

SELECT user_id, flatten(event_name) AS event_history, collect_set(flatten(array_distinct(items.item_id))) AS cart_history FROM events GROUP BY user_id;

SELECT user_id, array_distinct(event_name) AS event_history, collect_set(array_distinct(flatten(items:item_id))) AS cart_history FROM events GROUP BY user_id;

SELECT user_id, array_distinct(event_name) AS event_history, collect_set(flatten(explode(items.*))) AS cart_history FROM events GROUP BY user_id;