I am actually stuck in 3-tier structure. I surfed the internet and found two terminologies \"Database Abstraction Layer\" &开发者_Python百科amp; \"Data Access Layer\".
3 tables: items(item_id, ...) tags(item_id, tag_name) downloads(item_id, ...) How do I select a single item together with the number of occurrences of this item in the downloads table and all tag_nam
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