I love postgres json aggregates, but since postgres cant do nested aggregates it is kinda limiting when I would like to build my whole query response in a single postgres query
[0] : https://medium.com/r3d-buck3t/command-execution-with-postgre...
Nested aggregates in databases are useful when you want to perform calculations or summaries on groups of data within larger groups. For example, imagine you have a database of sales transactions with products and categories. You could use nested aggregates to find the total sales for each category and then calculate the average sales per category. It saves effort by allowing you to perform calculations at different levels of granularity in a single query.
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Use cases:[2]
autoparts inventory (book keeping page statics of sales/sales person, parts, inventory on hand, etc)
internet statistics for through put on all interfaces on group of servers [0]
--- topic related books:
Joe Celko has book series 'SQL for Smarties' that covers basic through advanced aggrecation with sql using example queries.
Joe Celko's 'Trees and Hierarchies in SQL for Smarties' covers some of the ideas related to 'SQL statment returned a database'?
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[0]: https://dba.stackexchange.com/questions/173044/nested-aggreg...
[1] : http://unicon.org/
[2] : https://cs.uwaterloo.ca/~tozsu/courses/CS338/lectures/6%20Ne...
You can do an array aggregate to get all users and their posts in the array, with build_jsonb_object you can make the posts an object of say id and content. But then you can't really make another array aggregate per post.
[0] : https://medium.com/r3d-buck3t/command-execution-with-postgre...