I have user, items and user_items tables, and as usual user has many items. Tables contains: User: ~50K Items: ~3.5M UserItems: ~5M
I am using MySQL and most of my queries are selecting items of a user. So I wonder If it helps to keep data on UserItems table as follows,
user_id item_ids 1 1,22,23,45,66...
Then after getting ids, simply parse to get item ids. Any suggestion/experience?